Run Fueling

Time-restricted eating effects on performance, immune function, and body composition in elite cyclists: a randomized controlled trial

Tatiana Moro, Grant M. Tinsley, Giovanni Longo +8 more · Journal of the International Society of Sports Nutrition · 2020 · 139 citations

Four weeks of time-restricted eating (16-hour daily fast, 8-hour eating window) in elite cyclists caused a 2% body weight loss and 1.1% reduction in body fat percentage without losing muscle mass, did not impair cycling performance, and reduced inflammation markers — but also lowered anabolic hormones (free testosterone and IGF-1), which could be a concern for long-term training adaptations.

The Impact of Individualizing Sodium Bicarbonate Supplementation Strategies on World-Class Rowing Performance

Susan Boegman, Trent Stellingwerff, G. Shaw +4 more · Frontiers in Nutrition · 2020 · 37 citations

Timing sodium bicarbonate (baking soda) ingestion to match each athlete's individual peak blood bicarbonate level improved 2,000-meter rowing time-trial performance by an average of 2 seconds compared to a standard fixed timing protocol, but the effect was small and the mechanism remains unclear.

Crisis of confidence averted: Impairment of exercise economy and performance in elite race walkers by ketogenic low carbohydrate, high fat (LCHF) diet is reproducible

Louise M. Burke, Avish P. Sharma, Ida A. Heikura +7 more · PLoS ONE · 2020 · 96 citations

A ketogenic low-carbohydrate, high-fat (LCHF) diet increased fat burning but made elite race walkers less efficient and slower over 10,000 m, and a 2.5-week return to high-carb eating did not rescue performance — meaning the keto diet is likely harmful for high-intensity endurance performance, even as a short-term strategy.

2023 International Olympic Committee’s (IOC) consensus statement on Relative Energy Deficiency in Sport (REDs)

Margo Mountjoy, Kathryn E. Ackerman, David M. Bailey +14 more · British Journal of Sports Medicine · 2023 · 539 citations

This consensus statement synthesises over 170 new studies since 2018 to define Relative Energy Deficiency in Sport (REDs) as a syndrome caused by low energy availability (LEA)—not eating enough to cover exercise energy expenditure—that impairs health and performance in both female and male athletes, and introduces a new clinical assessment tool and physiological model to guide diagnosis, prevention, and treatment.

IOC consensus statement: dietary supplements and the high-performance athlete

Ronald J. Maughan, Louise M. Burke, Jiří Dvořák +22 more · British Journal of Sports Medicine · 2018 · 933 citations

Nutrition usually makes a small but potentially valuable contribution to successful performance in elite athletes, and dietary supplements can make a minor contribution to this nutrition program. Nonetheless, supplement use is widespread at all levels of sport. Products described as supplements target different issues, including the management of micronutrient deficiencies, supply of convenient forms of energy and macronutrients, and provision of direct benefits to performance or indirect benefits such as supporting intense training regimens. The appropriate use of some supplements can offer benefits to the athlete, but others may be harmful to the athlete's health, performance, and/or livelihood and reputation if an anti-doping rule violation results. A complete nutritional assessment should be undertaken before decisions regarding supplement use are made. Supplements claiming to directly or indirectly enhance performance are typically the largest group of products marketed to athletes, but only a few (including caffeine, creatine, specific buffering agents and nitrate) have good evidence of benefits. However, responses are affected by the scenario of use and may vary widely between individuals because of factors that include genetics, the microbiome, and habitual diet. Supplements intended to enhance performance should be thoroughly trialed in training or simulated competition before implementation in competition. Inadvertent ingestion of substances prohibited under the anti-doping codes that govern elite sport is a known risk of taking some supplements. Protection of the athlete's health and awareness of the potential for harm must be paramount, and expert professional opinion and assistance is strongly advised before embarking on supplement use.

Sports Drinks on the Edge of a New Era

Shaun Sutehall, Borja Muñiz-Pardos, Andrew N. Bosch +2 more · Current Sports Medicine Reports · 2018 · 30 citations

Introduction Since the first modern Olympics in 1896 in Athens, fluid intake and carbohydrate (CHO) delivery practices during sports and exercise have varied greatly, reflecting the uncertainty and lack of agreement within the scientific community. The present perspective serves to summarize some of the most important milestones and advances in scientific knowledge that has shaped current recommendations in fluid and CHO intake during exercise and to encourage new research paradigms that embrace novel advances in technology and personal medicine. There are only a few places on earth where human beings survive solely by persistence hunting. In the Kalahiri region of South Africa, the San tribe survival requires tracking prey over difficult terrain and running it down at high speeds in severe ambient conditions (46°C/115°F) until either man (the hunter) or animal (the hunted) collapses (1). During a chase, high metabolic heat production during the short, intense exercise combined with an impaired ability to lose heat would cause the core temperature (Tc) of the prey (e.g., antelope) to rise with each subsequent sprint until the elevated Tc caused the animal to collapse to the ground. To compensate for the lack of sufficient speed, savanna-adapted humans developed several evolutionary adaptations, such as a higher sweat rate allowing the dissipation of metabolic heat production to the environment, a bipedal posture which reduced the heat gained from solar radiation and an enhanced ability to perform aerobic exercise for prolonged durations compared with their prey. Humans living as hunter gatherers with these evolutionary adaptations migrated from Africa as recently as 50,000 to 60,000 yr ago and spread throughout Africa, Eurasia, Oceania, and the Americas. In comparison to other large mammals and most animals considered excellent runners, antelopes, cheetahs, horses, and dogs, modern day humans are better designed to perform prolonged endurance exercise in the heat. In the early 1900s, there was a clear lack of knowledge in the area of hydration and endurance performance. For example, at the 1904 Olympic marathon in St. Louis, on a hot and humid summer day, 32 runners began the 24.85-mile-long course with water being provided at only two stations (2). There was widespread belief during this time that drinking during exercise was unnecessary and to compete without nourishment was a worthy achievement. As such, there was little research interest in carbohydrate (CHO) and fluid consumption during sport and exercise. However, in 1923, exercise physiology advanced significantly with the pioneering research of A.V. Hill, with seminal studies investigating the limits of maximal exercise that stressed the importance of maintaining blood supply to the exercising skeletal muscles and the heart during maximal exercise as reflected in the following extract (3): “A heart, adequate in every other way, might fail to allow its owner to undertake severe continued effort, simply because of the imperfect arrangement of its own supply of blood.” A.V. Hill (1923) Hill termed this inhibition of the heart, “the governor” that protected against increases in cardiac output (Q˙) that could result in too great a mismatch between oxygen delivery and oxygen consumption of the heart, potentially leading to a myocardial infarction. This research was the primary impetus for the advancement of the “cardiovascular” model of physiology and thermoregulation that represents the basis of much of the subsequent research into fluid consumption during sport and exercise. The cardiovascular model of thermoregulation has been used to explain the consequences of an excessive water loss (4). This model contends that the reduction in plasma volume (PV) (caused predominately through sweating) during exercise induces a concurrent rise in Q˙ to maintain blood flow to the exercising muscles and the skin (4–6). If the decline in PV was to continue, the model predicts that there is a point at which increases in heart rate can no longer compensate for the reduction in stroke volume and therefore Q˙ must decline (7). In this situation, mean arterial pressure will be protected by increasing vascular resistance, leading to reduced blood flow to the skin, increasing Tc and potentially leading to heat stroke (8). Wyndham and Strydom (8) in 1969 were among the first to propose that dehydration negatively influenced exercise performance. They reported a strong correlation between the rise in Tc and percentage water deficit in 20 athletes during two marathons. Notably, their fastest runner incurred a deficit of 4.3% and 4.8% in the first and second marathon, respectively; suggesting the effect of dehydration in excess of 2% body mass loss is not necessarily detrimental to performance. The cardiovascular model of exercise physiology/thermoregulation prevailed in different guises for the next four decades and is reflected in several consensus statements on exercise and fluid replacement (9,10). In 1996, it was advised that athletes undertaking exercise should drink fluids at a rate that matched fluid loss via sweat as best practice for preventing the negative symptoms associated with dehydration (i.e., decreased PV, increased cardiac strain and decreased performance) (11). This recommendation was reached based on several studies demonstrating the potentially negative effects of dehydration such as impaired skin blood flow and decreased Q˙ which could ultimately lead to heat stroke (12–14). In 2007, the American College of Sports Medicine (ACSM) released a revised consensus statement regarding fluid consumption during exercise, suggesting that preventing all dehydration may be unnecessary and that there may exist a level of “tolerable dehydration” (15). Since then, there has been substantial research into hydration and performance that would appear to support the position that there exists a level of dehydration due to sweating, about 2% body mass loss, above which exercise performance is impaired (16,17). Some of the literature on this topic, such as the article written by Wyndham and Strydom in 1969, seem to ignore or downplay the observation that the best performing athletes also were the most dehydrated as assessed by a loss in body mass. For example, using data from a review, when the relationship between running speed and percentage dehydration was plotted, the best-performing runner was dehydrated by some 8%, while the only runner to prevent body mass loss of >2% was the slowest (Fig. 1), suggesting dehydration at this modest level did not impair performance significantly (17,18).Figure 1: Finish time and % body mass loss due to dehydration. The fastest runner was the most dehydrated (~8%) and the slowest runner the least dehydrated (~1.9%) (17).It has been proposed that when one or more bodily systems are stressed beyond capacity and in order to prevent a cardiovascular “catastrophe” (i.e., myocardial infarction in the worse case scenario), exercise intensity is dramatically reduced (19,20). There may exist a “central governor” which responds to sensory feedback from multiple organs and tissues and regulates the extent of skeletal muscle recruitment during exercise to attenuate the rate of heat storage and prevent heat stroke (21,22). A similar concept sometimes referred to as the anticipatory model of thermoregulation has gained popularity (23). The idea is that exercise in the heat is terminated or intensity reduced due to a downregulation of muscle drive by the central nervous system in response to the rate at which Tc increases (i.e., to avoid a “catastrophe”). There are striking similarities between the different ideas suggesting that they may be describing similar/related phenomena. Deciding which is closer to the truth is conceptually difficult because we use the brain to study the brain. Ideas on dehydration have divided current opinion and it remains unclear if the fastest and most dehydrated runners in some of the aforementioned studies would have benefited from a better maintenance of hydration (to <2% body mass loss) or if the runners benefited from greater levels of dehydration — e.g., improved running economy. More recent research has suggested that it was not dehydration per se that impaired performance but rather whole-body hyperthermia (24). In this study, participants were placed under sufficient heat stress to either acutely raise skin temperature or raise skin temperature and Tc. It was found that an elevated skin temperature did not impair exercise performance, whereas the increase in whole body temperature did (24). In this context, a high sweat rate and a subsequent water deficit are the consequence of preventing hyperthermia and the high fluid loss seen in many of the fastest runners in previous studies. This may have allowed the faster athletes to continue producing higher metabolic heat (i.e., run faster) than the slower runners as more heat is dissipated to the environment (8,17). In 1970, Costill et al. (25) demonstrated the efficacy of a novel electrolyte/glucose drink on maintaining CHO metabolism during prolonged running. This study compared running for 2 h at 70% of maximal oxygen uptake (V˙O2max) while ingesting either a CHO drink containing glucose and electrolytes or water. Both drinks resulted in a levelling-off in core temperature after 45 min, whereas only with glucose ingestion was electrolyte balance and CHO metabolism maintained. Following this initial research into CHO ingestion during exercise, optimizing the formulation of CHO drinks became a popular area of research. For example, in 1970, there were 59 publications related to “exercise” and “carbohydrate,” whereas in 2017, there were 849, demonstrating the rapid increase in scientific interest in this area over the last ~50 years. It is now well accepted that CHO ingestion in various forms improves endurance performance by maintaining blood glucose and muscle glycogen stores (26) and research is now focused on determining the optimal mix of CHO (e.g., glucose, maltodextrin, fructose, sucrose and galactose) (27,28). The current literature suggests that the optimum mix of CHO is a maltodextrin and fructose approaching a 1:1 ratio (28). Maltodextrin is preferred over glucose due to the lower osmolality for a given energy density that does not inhibit gastric emptying to the same extent as glucose (29). The use of glucose/maltodextrin as a single source of CHO elicits an exogenous CHO oxidation rate of ~1.1 g·min−1 when administered at a rate of ~2.4 g·min−1 (30). Jeukendrup et al. (31) compared the ingestion rates of ~0.5 g·min−1 and ~2.7 g·min−1 during exercise. In both trials, there was a reduced fat oxidation, increased rate of appearance and disappearance of glucose and increased exogenous CHO oxidation, whereas in the ~2.7 g·min−1 trial, liver glycogen breakdown was inhibited. Despite the ingestion of a large amount of glucose, exogenous CHO oxidation did not exceed 1 g·min−1. The addition of fructose as a second CHO source has been shown to increase exogenous CHO oxidation through the utilisation of different transporters required to uptake glucose/fructose in the intestine. Glucose is absorbed into the blood via the sodium-dependent glucose co-transporter (SGLT1) and a glucose transporter (GLUT2), whereas fructose is primarily transported through a separate glucose transporter (GLUT5) via facilitated diffusion and GLUT2 (32) (Fig. 2). The combination of maltodextrin and fructose has repeatedly been shown to increase exogenous CHO oxidation compared with glucose-only ingestion up to a maximum of 1.8 g·min−1 (34).Figure 2: Glucose and fructose transporter routes across the intestinal lumen into the circulation. Adapted from Jeukendrup et al., 2015 (33).Current ACSM guidelines recommend the ingestion of 30 to 60 g·h−1 during prolonged endurance exercise lasting between 1 and 2.5 h and up to 90 g·h−1 during ultraendurance exercise exceeding 2 h (35). While these recommendations are generally well accepted, there is research that suggests no further benefit of ingesting CHO in excess of about 60 g·h−1 under more realistic conditions (e.g., breakfast before the trial commencing) (36). However, this position is not universally accepted. A recent systematic review assessed the existing evidence related to CHO intake and running performance (37). The authors suggest that CHO beverages with a concentration of 5.0% to 6.9% are the most beneficial in improving running performance. When the concentration increases above this, CHO feedings can cause gastrointestinal (GI) discomfort during intense running, lasting 60 to 90 min, mainly due to physical distortion of the GI region while running (38). A recent innovation for providing fluid and CHO during exercise is the use of alginate. Alginate is a naturally occurring anionic polymer typically derived from seaweed and is commonly used in oral drug delivery, wound healing, and tissue engineering due to its high biocompatibility and ease of gelation (39). The formulation of an alginate hydrogel can be tailored to form in a low pH environment that allows the hydrogel to encapsulate substrates or compounds of choice. The hydrogel subsequently dissolves in an environment with a much higher pH (i.e., the intestine), releasing the substrates or compound(s) (40). When an alginate-CHO mixture reaches the gastric fluid in the stomach, a hydrogel will form and encapsulate the CHO contained within the solution. The encapsulated CHO passes into the proximal section of the duodenum, without activating the glucose receptors and subsequently gastric emptying will not be reduced as is typically the case with the ingestion of high CHO drinks (29). This novel fuel delivery system permits the ingestion of higher amounts of CHO without the associated inhibition of gastric emptying which typically occurs when CHO drinks are ingested, allowing increased water uptake (41,42). To test this new concept, we recently conducted a pilot study in well-trained Kenyan athletes to investigate the effects of alginate hydrogel as a unique fluid and CHO delivery system. A secondary aim was to determine the loss in body mass in well-trained Kenyan runners drinking ad libitum during strenuous exercise conducted at moderate altitude (approximately 2000 m above sea level) to estimate the levels of dehydration. For this pilot study, 16 well-trained Kenyan runners provided written consent to be part of the study and provided near nude body mass before and after the training runs. The average body mass before the run was 54.0 ± 3.9 kg. The training run was 25.1 km, with an average temperature of 20.1°C and relative humidity of 37%. The average pace was 3:48 min·km−1 and the run was completed within 95 min; the change in altitude during the run was approximately 500 m. A CHO drink containing approximately 40 to 50 g·L−1 CHO was provided to all athletes every 5 km in sufficient volume to allow drinking ad libitum. Four athletes were provided with either 180 g·L−1 or 300 g·L−1 CHO using alginate hydrogel (i.e., maltodextrin to fructose ratio of 1:0.7). Drinking bottles were collected following each 5 km station to assess fluid consumption; the bottles of one athlete were damaged during the run and thus this data has been omitted. After the completion of the run, the average body mass was 51.7 ± 3.7 kg, representing a water deficit of 4.2 ± 1.0% body mass loss, with a range of 2.2% to 5.9%. For the three athletes using the alginate hydrogel drink, 291.3 ± 26.4 mL was consumed over the 95 min. While this research is ongoing, there are some encouraging preliminary findings. Firstly, all athletes failed to prevent a decrease in body mass of ≤2% despite having regular access to sports drinks. Secondarily, there were no reports of any GI distress with any drink including the alginate hydrogel. Although the volumes consumed were fairly modest, the use of alginate hydrogel as high as 300 g·L-1 of CHO was well tolerated, illustrating the unique ability of hydrogels to provide CHO in concentrations that far exceed what can typically be tolerated using commercially available sports drinks. Although there is only indirect evidence for its ergogenic effect, the winners of the 2016/2017 Berlin, Chicago, New York, Tokyo, Boston, and London marathons all used a CHO beverage containing alginate hydrogel, demonstrating its popularity in the elite field (43). Given its potential, further research is required to quantify the effect of alginate hydrogel on exogenous CHO oxidation and gastric emptying rates before the efficacy of this new delivery system can be confirmed. For example, the provision of a high concentration of CHO during exercise using this innovation can easily be modified to deliver other essential substrates/nutrients that may otherwise not be so well tolerated by the GI tract, such as protein (40) and iron status regulating drugs (44). If the efficacy of this innovative fuel and fluid delivery system is confirmed, this will represent significant progress toward the development of a personalised next generation sports drink containing a specific combination of substrates/nutrients for the athlete for any given situation. Dental health should be considered when choosing to use a sports drink. The International Olympic Committee provides comprehensive dental treatment during the Olympic Games to all competing athletes (45). In particular, cavities and dental erosion are among the most commonly reported dental issues in athletes with incidents up to 75% and 86%, respectively, and is likely a result of a diet that contains a high amount of CHO supplements which often contain flavorings, such as citric acid (46–48). Commonly consumed sports drinks have a low pH (i.e., 2.4-4.5) and therefore, these beverages could be a contributing factor in the dental problems seen in athletes (48). When using an alginate hydrogel, the beverage requires a relatively neutral pH with the encapsulation process beginning only when contact is made with gastric secretions in the stomach. In theory, a CHO beverage containing alginate hydrogel may be superior from a dental health perspective and could aid in reducing dental cavities in elite athletes. A survey at the London 2012 Olympic Games found that 18% of athletes reported that their oral health had a negative impact on their performance and 46.5% had not been to a dentist in the past year (45). The latest consensus statement aims to address such issues by oral health into the of sports health and health research area of interest is the use of systems to assess the drinking of athletes during training and in such as systems that can flow rate through an drink and can estimate drinking rate are beginning to to the suggested hydration of each providing feedback to and athletes through a hydration with a sweat to the hydration of This technology could be used in combination with other technology allowing several to be and in allowing for an regarding fluid intake and CHO delivery during exercise have change over the past reflecting different of regarding the scientific This perspective some of the milestones and in scientific opinion the current recommendations for fluid and fuel intake during exercise and to encourage new research paradigms to advances in technology and personal medicine. Despite that dehydration in excess of 2% body mass loss during exercise performance, the of this position in elite in running, is and some data with to body mass during no symptoms or of research into sports drinks is primarily focused on optimizing the mix to increase the rate of exogenous CHO of CHO could represent a new in the process of research is required to quantify the effects on the rate of gastric emptying and exogenous CHO oxidation rate of this in sports drinks.

Pomegranate Extract Improves Maximal Performance of Trained Cyclists after an Exhausting Endurance Trial: A Randomised Controlled Trial

Antonio Torregrosa-García, Vicente Ávila-Gandía, Antonio J. Luque-Rubia +3 more · Nutrients · 2019 · 36 citations

Taking 225 mg of punicalagins (from pomegranate extract) daily for 15 days helped trained cyclists ride ~94 seconds longer to exhaustion after a fatiguing endurance bout, compared to placebo — suggesting pomegranate extract may boost late-stage performance when you're already tired.

Nutritional Ketosis Alters Fuel Preference and Thereby Endurance Performance in Athletes

Pete J. Cox, Tom Kirk, Tom Ashmore +15 more · Cell Metabolism · 2016 · 520 citations

IOC Consensus Statement: Dietary Supplements and the High-Performance Athlete

Ronald J. Maughan, Louise M. Burke, Jiří Dvořák +22 more · International Journal of Sport Nutrition and Exercise Metabolism · 2018 · 506 citations

Nutrition usually makes a small but potentially valuable contribution to successful performance in elite athletes, and dietary supplements can make a minor contribution to this nutrition program. Nonetheless, supplement use is widespread at all levels of sport. Products described as supplements target different issues, including the management of micronutrient deficiencies, supply of convenient forms of energy and macronutrients, and provision of direct benefits to performance or indirect benefits such as supporting intense training regimens. The appropriate use of some supplements can offer benefits to the athlete, but others may be harmful to the athlete’s health, performance, and/or livelihood and reputation if an anti-doping rule violation results. A complete nutritional assessment should be undertaken before decisions regarding supplement use are made. Supplements claiming to directly or indirectly enhance performance are typically the largest group of products marketed to athletes, but only a few (including caffeine, creatine, specific buffering agents and nitrate) have good evidence of benefits. However, responses are affected by the scenario of use and may vary widely between individuals because of factors that include genetics, the microbiome, and habitual diet. Supplements intended to enhance performance should be thoroughly trialed in training or simulated competition before implementation in competition. Inadvertent ingestion of substances prohibited under the anti-doping codes that govern elite sport is a known risk of taking some supplements. Protection of the athlete’s health and awareness of the potential for harm must be paramount, and expert professional opinion and assistance is strongly advised before embarking on supplement use.

Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers

Louise M. Burke, Megan L. Ross, Laura A. Garvican‐Lewis +8 more · The Journal of Physiology · 2016 · 400 citations

Key points Three weeks of intensified training and mild energy deficit in elite race walkers increases peak aerobic capacity independent of dietary support. Adaptation to a ketogenic low carbohydrate, high fat (LCHF) diet markedly increases rates of whole‐body fat oxidation during exercise in race walkers over a range of exercise intensities. The increased rates of fat oxidation result in reduced economy (increased oxygen demand for a given speed) at velocities that translate to real‐life race performance in elite race walkers. In contrast to training with diets providing chronic or periodised high carbohydrate availability, adaptation to an LCHF diet impairs performance in elite endurance athletes despite a significant improvement in peak aerobic capacity. Abstract We investigated the effects of adaptation to a ketogenic low carbohydrate (CHO), high fat diet (LCHF) during 3 weeks of intensified training on metabolism and performance of world‐class endurance athletes. We controlled three isoenergetic diets in elite race walkers: high CHO availability (g kg −1 day −1 : 8.6 CHO, 2.1 protein, 1.2 fat) consumed before, during and after training (HCHO, n = 9); identical macronutrient intake, periodised within or between days to alternate between low and high CHO availability (PCHO, n = 10); LCHF (&lt; 50 g day −1 CHO; 78% energy as fat; 2.1 g kg −1 day −1 protein; LCHF, n = 10). Post‐intervention, during race walking increased in all groups ( P &lt; 0.001, 90% CI: 2.55, 5.20%). LCHF was associated with markedly increased rates of whole‐body fat oxidation, attaining peak rates of 1.57 ± 0.32 g min −1 during 2 h of walking at ∼80% . However, LCHF also increased the oxygen (O 2 ) cost of race walking at velocities relevant to real‐life race performance: O 2 uptake (expressed as a percentage of new ) at a speed approximating 20 km race pace was reduced in HCHO and PCHO (90% CI: −7.047, −2.55 and −5.18, −0.86, respectively), but was maintained at pre‐intervention levels in LCHF. HCHO and PCHO groups improved times for 10 km race walk: 6.6% (90% CI: 4.1, 9.1%) and 5.3% (3.4, 7.2%), with no improvement (−1.6% (−8.5, 5.3%)) for the LCHF group. In contrast to training with diets providing chronic or periodised high‐CHO availability, and despite a significant improvement in , adaptation to the topical LCHF diet negated performance benefits in elite endurance athletes, in part due to reduced exercise economy.

UEFA expert group statement on nutrition in elite football. Current evidence to inform practical recommendations and guide future research

James Collins, Ronald J. Maughan, Michael Gleeson +28 more · British Journal of Sports Medicine · 2020 · 269 citations

Football is a global game which is constantly evolving, showing substantial increases in physical and technical demands. Nutrition plays a valuable integrated role in optimising performance of elite players during training and match-play, and maintaining their overall health throughout the season. An evidence-based approach to nutrition emphasising, a 'food first' philosophy (ie, food over supplements), is fundamental to ensure effective player support. This requires relevant scientific evidence to be applied according to the constraints of what is practical and feasible in the football setting. The science underpinning sports nutrition is evolving fast, and practitioners must be alert to new developments. In response to these developments, the Union of European Football Associations (UEFA) has gathered experts in applied sports nutrition research as well as practitioners working with elite football clubs and national associations/federations to issue an expert statement on a range of topics relevant to elite football nutrition: (1) match day nutrition, (2) training day nutrition, (3) body composition, (4) stressful environments and travel, (5) cultural diversity and dietary considerations, (6) dietary supplements, (7) rehabilitation, (8) referees and (9) junior high-level players. The expert group provide a narrative synthesis of the scientific background relating to these topics based on their knowledge and experience of the scientific research literature, as well as practical experience of applying knowledge within an elite sports setting. Our intention is to provide readers with content to help drive their own practical recommendations. In addition, to provide guidance to applied researchers where to focus future efforts.

Auditing the Representation of Female Versus Male Athletes in Sports Science and Sports Medicine Research: Evidence-Based Performance Supplements

Ella S. Smith, Alannah K. A. McKay, Megan A. Kuikman +5 more · Nutrients · 2022 · 88 citations

Although sports nutrition guidelines promote evidence-based practice, it is unclear whether women have been adequately included in the underpinning research. In view of the high usage rates of performance supplements by female athletes, we conducted a standardised audit of the literature supporting evidence-based products: β-alanine, caffeine, creatine, glycerol, nitrate/beetroot juice and sodium bicarbonate. Within 1826 studies totalling 34,889 participants, just 23% of participants were women, although 34% of studies included at least one woman. Across different supplements, 0-8% of studies investigated women exclusively, while fewer (0-2%) were specifically designed to compare sex-based responses. The annual publication of female-specific studies was ~8 times fewer than those investigating exclusively male cohorts. Interestingly, 15% of the female participants were classified as international/world-class athletes, compared with 7% of men. Most studies investigated performance outcomes but displayed poorer representation of women (16% of participants), whereas health-focussed studies had the greatest proportion of female participants (35%). Only 14% of studies including women attempted to define menstrual status, with only three studies (~0.5%) implementing best practice methodologies to assess menstrual status. New research should target the efficacy of performance supplements in female athletes, and future sports nutrition recommendations should specifically consider how well female athletes have contributed to the evidence-base.

Nutritional Factors That Influence Change in Bone Density and Stress Fracture Risk Among Young Female Cross‐Country Runners

Jeri W. Nieves, Kathryn Melsop, Meredith Curtis +5 more · PM&R · 2010 · 178 citations

OBJECTIVE: To identify nutrients, foods, and dietary patterns associated with stress fracture risk and changes in bone density among young female distance runners. DESIGN AND SETTING: Two-year, prospective cohort study. Observational data were collected in the course of a multicenter randomized trial of the effect of oral contraceptives on bone health. PARTICIPANTS: One hundred and twenty-five female competitive distance runners ages 18-26 years. ASSESSMENT OF RISK FACTORS: Dietary variables were assessed with a food frequency questionnaire. MAIN OUTCOME MEASUREMENTS: Bone mineral density and content (BMD/BMC) of the spine, hip, and total body were measured annually by dual x-ray absorptiometry (DEXA). Stress fractures were recorded on monthly calendars, and had to be confirmed by radiograph, bone scan, or magnetic resonance imaging. RESULTS: Seventeen participants had at least one stress fracture during follow-up. Higher intakes of calcium, skim milk, and dairy products were associated with lower rates of stress fracture. Each additional cup of skim milk consumed per day was associated with a 62% reduction in stress fracture incidence (P < .05); and a dietary pattern of high dairy and low fat intake was associated with a 68% reduction (P < .05). Higher intakes of skim milk, dairy foods, calcium, animal protein, and potassium were associated with significant (P < .05) gains in whole-body BMD and BMC. Higher intakes of calcium, vitamin D, skim milk, dairy foods, potassium, and a dietary pattern of high dairy and low fat were associated with significant gains in hip BMD. CONCLUSIONS: In young female runners, low-fat dairy products and the major nutrients in milk (calcium, vitamin D, and protein) were associated with greater bone gains and a lower stress fracture rate. Potassium intake was also associated with greater gains in hip and whole-body BMD.

International Association of Athletics Federations Consensus Statement 2019: Nutrition for Athletics

Louise M. Burke, L M Castell, Douglas J. Casa +13 more · International Journal of Sport Nutrition and Exercise Metabolism · 2019 · 233 citations

The International Association of Athletics Federations recognizes the importance of nutritional practices in optimizing an Athlete's well-being and performance. Although Athletics encompasses a diverse range of track-and-field events with different performance determinants, there are common goals around nutritional support for adaptation to training, optimal performance for key events, and reducing the risk of injury and illness. Periodized guidelines can be provided for the appropriate type, amount, and timing of intake of food and fluids to promote optimal health and performance across different scenarios of training and competition. Some Athletes are at risk of relative energy deficiency in sport arising from a mismatch between energy intake and exercise energy expenditure. Competition nutrition strategies may involve pre-event, within-event, and between-event eating to address requirements for carbohydrate and fluid replacement. Although a "food first" policy should underpin an Athlete's nutrition plan, there may be occasions for the judicious use of medical supplements to address nutrient deficiencies or sports foods that help the athlete to meet nutritional goals when it is impractical to eat food. Evidence-based supplements include caffeine, bicarbonate, beta-alanine, nitrate, and creatine; however, their value is specific to the characteristics of the event. Special considerations are needed for travel, challenging environments (e.g., heat and altitude); special populations (e.g., females, young and masters athletes); and restricted dietary choice (e.g., vegetarian). Ideally, each Athlete should develop a personalized, periodized, and practical nutrition plan via collaboration with their coach and accredited sports nutrition experts, to optimize their performance.

Exercise training modulates the gut microbiota profile and impairs inflammatory signaling pathways in obese children

Rocío Quiroga, Esther Nistal, Brisamar Estébanez +8 more · Experimental & Molecular Medicine · 2020 · 208 citations

Childhood obesity has reached epidemic levels and is a serious health concern associated with metabolic syndrome, nonalcoholic fatty liver disease, and gut microbiota alterations. Physical exercise is known to counteract obesity progression and modulate the gut microbiota composition. This study aims to determine the effect of a 12-week strength and endurance combined training program on gut microbiota and inflammation in obese pediatric patients. Thirty-nine obese children were assigned randomly to the control or training group. Anthropometric and biochemical parameters, muscular strength, and inflammatory signaling pathways in mononuclear cells were evaluated. Bacterial composition and functionality were determined by massive sequencing and metabolomic analysis. Exercise reduced plasma glucose levels and increased dynamic strength in the upper and lower extremities compared with the obese control group. Metagenomic analysis revealed a bacterial composition associated with obesity, showing changes at the phylum, class, and genus levels. Exercise counteracted this profile, significantly reducing the Proteobacteria phylum and Gammaproteobacteria class. Moreover, physical activity tended to increase some genera, such as Blautia, Dialister, and Roseburia, leading to a microbiota profile similar to that of healthy children. Metabolomic analysis revealed changes in short-chain fatty acids, branched-chain amino acids, and several sugars in response to exercise, in correlation with a specific microbiota profile. Finally, the training protocol significantly inhibited the activation of the obesity-associated NLRP3 signaling pathway. Our data suggest the existence of an obesity-related deleterious microbiota profile that is positively modified by physical activity intervention. Exercise training could be considered an efficient nonpharmacological therapy, reducing inflammatory signaling pathways induced by obesity in children via microbiota modulation.

Significant Molecular and Systemic Adaptations after Repeated Sprint Training in Hypoxia

Raphaël Faiss, Bertrand Léger, Jean-Marc Vésin +4 more · PLoS ONE · 2013 · 281 citations

While intermittent hypoxic training (IHT) has been reported to evoke cellular responses via hypoxia inducible factors (HIFs) but without substantial performance benefits in endurance athletes, we hypothesized that repeated sprint training in hypoxia could enhance repeated sprint ability (RSA) performed in normoxia via improved glycolysis and O(2) utilization. 40 trained subjects completed 8 cycling repeated sprint sessions in hypoxia (RSH, 3000 m) or normoxia (RSN, 485 m). Before (Pre-) and after (Post-) training, muscular levels of selected mRNAs were analyzed from resting muscle biopsies and RSA tested until exhaustion (10-s sprint, work-to-rest ratio 1:2) with muscle perfusion assessed by near-infrared spectroscopy. From Pre- to Post-, the average power output of all sprints in RSA was increased (p<0.01) to the same extent (6% vs 7%, NS) in RSH and in RSN but the number of sprints to exhaustion was increased in RSH (9.4±4.8 vs. 13.0±6.2 sprints, p<0.01) but not in RSN (9.3±4.2 vs. 8.9±3.5). mRNA concentrations of HIF-1α (+55%), carbonic anhydrase III (+35%) and monocarboxylate transporter-4 (+20%) were augmented (p<0.05) whereas mitochondrial transcription factor A (-40%), peroxisome proliferator-activated receptor gamma coactivator 1α (-23%) and monocarboxylate transporter-1 (-36%) were decreased (p<0.01) in RSH only. Besides, the changes in total hemoglobin variations (Δ[tHb]) during sprints throughout RSA test increased to a greater extent (p<0.01) in RSH. Our findings show larger improvement in repeated sprint performance in RSH than in RSN with significant molecular adaptations and larger blood perfusion variations in active muscles.

Gut bacteria are critical for optimal muscle function: a potential link with glucose homeostasis

Kévin Nay, Maxence Jollet, Bénédicte Goustard +12 more · American Journal of Physiology-Endocrinology and Metabolism · 2019 · 206 citations

Gut microbiota is involved in the development of several chronic diseases, including diabetes, obesity, and cancer, through its interactions with the host organs. It has been suggested that the cross talk between gut microbiota and skeletal muscle plays a role in different pathological conditions, such as intestinal chronic inflammation and cachexia. However, it remains unclear whether gut microbiota directly influences skeletal muscle function. In this work, we studied the impact of gut microbiota modulation on mice skeletal muscle function and investigated the underlying mechanisms. We determined the consequences of gut microbiota depletion after treatment with a mixture of a broad spectrum of antibiotics for 21 days and after 10 days of natural reseeding. We found that, in gut microbiota-depleted mice, running endurance was decreased, as well as the extensor digitorum longus muscle fatigue index in an ex vivo contractile test. Importantly, the muscle endurance capacity was efficiently normalized by natural reseeding. These endurance changes were not related to variation in muscle mass, fiber typology, or mitochondrial function. However, several pertinent glucose metabolism markers, such as ileum gene expression of short fatty acid chain and glucose transporters G protein-coupled receptor 41 and sodium-glucose cotransporter 1 and muscle glycogen level, paralleled the muscle endurance changes observed after treatment with antibiotics for 21 days and reseeding. Because glycogen is a key energetic substrate for prolonged exercise, modulating its muscle availability via gut microbiota represents one potent mechanism that can contribute to the gut microbiota-skeletal muscle axis. Taken together, our results strongly support the hypothesis that gut bacteria are required for host optimal skeletal muscle function.

Ketogenic Diets Are Not Beneficial for Athletic Performance: Response to Noakes

LOUISE M. BURKE, Jamie Whitfield · Medicine & Science in Sports & Exercise · 2024 · 7 citations

Across 19 separate data points from studies of competitive endurance athletes, ketogenic diets (very low carbohydrate, high fat) consistently failed to improve real-world race performance compared to high-carbohydrate diets, with most studies showing either no difference or a clear detriment, and any apparent benefits were explained by methodological flaws like lack of randomization, order effects, or weight loss confounding.

Atlas of exercise metabolism reveals time-dependent signatures of metabolic homeostasis

Shogo Sato, Kenneth A. Dyar, Jonas T. Treebak +19 more · Cell Metabolism · 2022 · 193 citations

Tissue sensitivity and response to exercise vary according to the time of day and alignment of circadian clocks, but the optimal exercise time to elicit a desired metabolic outcome is not fully defined. To understand how tissues independently and collectively respond to timed exercise, we applied a systems biology approach. We mapped and compared global metabolite responses of seven different mouse tissues and serum after an acute exercise bout performed at different times of the day. Comparative analyses of intra- and inter-tissue metabolite dynamics, including temporal profiling and blood sampling across liver and hindlimb muscles, uncovered an unbiased view of local and systemic metabolic responses to exercise unique to time of day. This comprehensive atlas of exercise metabolism provides clarity and physiological context regarding the production and distribution of canonical and novel time-dependent exerkine metabolites, such as 2-hydroxybutyrate (2-HB), and reveals insight into the health-promoting benefits of exercise on metabolism.

Beneficial effects of exercise on gut microbiota functionality and barrier integrity, and gut-liver crosstalk in an <i>in vivo</i> model of early obesity and non-alcoholic fatty liver disease

Sara Carbajo‐Pescador, David Porras, María Victoria García‐Mediavilla +7 more · Disease Models & Mechanisms · 2019 · 184 citations

ABSTRACT Childhood obesity has reached epidemic levels, representing one of the most serious public health concerns associated with metabolic syndrome and non-alcoholic fatty liver disease (NAFLD). There is limited clinical experience concerning pediatric NAFLD patients, and thus the therapeutic options are scarce. The aim of this study was to evaluate the benefits of exercise on gut microbiota composition and functionality balance, and consequent effects on early obesity and NAFLD onset in an in vivo model. Juvenile (21-day-old) male Wistar rats fed a control diet or a high-fat diet (HFD) were subjected to a combined aerobic and resistance training protocol. Fecal microbiota was sequenced by an Illumina MiSeq system, and parameters related to metabolic syndrome, fecal metabolome, intestinal barrier integrity, bile acid metabolism and transport, and alteration of the gut-liver axis were measured. Exercise decreased HFD-induced body weight gain, metabolic syndrome and hepatic steatosis, as a result of its lipid metabolism modulatory capacity. Gut microbiota composition and functionality were substantially modified as a consequence of diet, age and exercise intervention. In addition, the training protocol increased Parabacteroides, Bacteroides and Flavobacterium genera, correlating with a beneficial metabolomic profile, whereas Blautia, Dysgonomonas and Porphyromonas showed an opposite pattern. Exercise effectively counteracted HFD-induced microbial imbalance, leading to intestinal barrier preservation, which, in turn, prevented deregulation of the gut-liver axis and improved bile acid homeostasis, determining the clinical outcomes of NAFLD. In conclusion, we provide scientific evidence highlighting the benefits of gut microbiota composition and functionality modulation by physical exercise protocols in the management of early obesity and NAFLD development.

Running economy: measurement, norms, and determining factors

Kyle R. Barnes, Andrew E. Kilding · Sports Medicine - Open · 2015 · 439 citations

Running economy (RE) is considered an important physiological measure for endurance athletes, especially distance runners. This review considers 1) how RE is defined and measured and 2) physiological and biomechanical factors that determine or influence RE. It is difficult to accurately ascertain what is good, average, and poor RE between athletes and studies due to variation in protocols, gas-analysis systems, and data averaging techniques. However, representative RE values for different caliber of male and female runners can be identified from existing literature with mostly clear delineations in oxygen uptake across a range of speeds in moderately and highly trained and elite runners. Despite being simple to measure and acceptably reliable, it is evident that RE is a complex, multifactorial concept that reflects the integrated composite of a variety of metabolic, cardiorespiratory, biomechanical and neuromuscular characteristics that are unique to the individual. Metabolic efficiency refers to the utilization of available energy to facilitate optimal performance, whereas cardiopulmonary efficiency refers to a reduced work output for the processes related to oxygen transport and utilization. Biomechanical and neuromuscular characteristics refer to the interaction between the neural and musculoskeletal systems and their ability to convert power output into translocation and therefore performance. Of the numerous metabolic, cardiopulmonary, biomechanical and neuromuscular characteristics contributing to RE, many of these are able to adapt through training or other interventions resulting in improved RE.

Fuel for the Work Required: A Theoretical Framework for Carbohydrate Periodization and the Glycogen Threshold Hypothesis

Samuel G. Impey, Mark A. Hearris, Kelly M. Hammond +4 more · Sports Medicine · 2018 · 224 citations

Deliberately training with reduced carbohydrate (CHO) availability to enhance endurance-training-induced metabolic adaptations of skeletal muscle (i.e. the 'train low, compete high' paradigm) is a hot topic within sport nutrition. Train-low studies involve periodically training (e.g., 30-50% of training sessions) with reduced CHO availability, where train-low models include twice per day training, fasted training, post-exercise CHO restriction and 'sleep low, train low'. When compared with high CHO availability, data suggest that augmented cell signalling (73% of 11 studies), gene expression (75% of 12 studies) and training-induced increases in oxidative enzyme activity/protein content (78% of 9 studies) associated with 'train low' are especially apparent when training sessions are commenced within a specific range of muscle glycogen concentrations. Nonetheless, such muscle adaptations do not always translate to improved exercise performance (e.g. 37 and 63% of 11 studies show improvements or no change, respectively). Herein, we present our rationale for the glycogen threshold hypothesis, a window of muscle glycogen concentrations that simultaneously permits completion of required training workloads and activation of the molecular machinery regulating training adaptations. We also present the 'fuel for the work required' paradigm (representative of an amalgamation of train-low models) whereby CHO availability is adjusted in accordance with the demands of the upcoming training session(s). In order to strategically implement train-low sessions, our challenge now is to quantify the glycogen cost of habitual training sessions (so as to inform the attainment of any potential threshold) and ensure absolute training intensity is not compromised, while also creating a metabolic milieu conducive to facilitating the endurance phenotype.

Interval training in the fed or fasted state improves body composition and muscle oxidative capacity in overweight women

Jenna B. Gillen, Michael E. Percival, Alison C. Ludzki +2 more · Obesity · 2013 · 224 citations

OBJECTIVE: To investigate the effects of low-volume high-intensity interval training (HIT) performed in the fasted (FAST) versus fed (FED) state on body composition, muscle oxidative capacity, and glycemic control in overweight/obese women. DESIGN AND METHODS: Sixteen women (27 ± 8 years, BMI: 29 ± 6 kg/m(2) , VO2peak : 28 ± 3 ml/kg/min) were assigned to either FAST or FED (n = 8 each) and performed 18 sessions of HIT (10× 60-s cycling efforts at ∼90% maximal heart rate, 60-s recovery) over 6 weeks. RESULTS: There was no significant difference between FAST and FED for any measured variable. Body mass was unchanged following training; however, dual energy X-ray absorptiometry revealed lower percent fat in abdominal and leg regions as well as the whole body level (main effects for time, P ≤ 0.05). Fat-free mass increased in leg and gynoid regions (P ≤ 0.05). Resting muscle biopsies revealed a training-induced increase in mitochondrial capacity as evidenced by increased maximal activities of citrate synthase and β-hydroxyacyl-CoA dehydrogenase (P ≤ 0.05). There was no change in insulin sensitivity, although change in insulin area under the curve was correlated with change in abdominal percent fat (r = 0.54, P ≤ 0.05). CONCLUSION: Short-term low-volume HIT is a time-efficient strategy to improve body composition and muscle oxidative capacity in overweight/obese women, but fed- versus fasted-state training does not alter this response.

Carnitine Insufficiency Caused by Aging and Overnutrition Compromises Mitochondrial Performance and Metabolic Control

Robert C. Noland, Timothy R. Koves, Sarah E. Seiler +6 more · Journal of Biological Chemistry · 2009 · 315 citations

In addition to its essential role in permitting mitochondrial import and oxidation of long chain fatty acids, carnitine also functions as an acyl group acceptor that facilitates mitochondrial export of excess carbons in the form of acylcarnitines. Recent evidence suggests carnitine requirements increase under conditions of sustained metabolic stress. Accordingly, we hypothesized that carnitine insufficiency might contribute to mitochondrial dysfunction and obesity-related impairments in glucose tolerance. Consistent with this prediction whole body carnitine diminution was identified as a common feature of insulin-resistant states such as advanced age, genetic diabetes, and diet-induced obesity. In rodents fed a lifelong (12 month) high fat diet, compromised carnitine status corresponded with increased skeletal muscle accumulation of acylcarnitine esters and diminished hepatic expression of carnitine biosynthetic genes. Diminished carnitine reserves in muscle of obese rats was accompanied by marked perturbations in mitochondrial fuel metabolism, including low rates of complete fatty acid oxidation, elevated incomplete beta-oxidation, and impaired substrate switching from fatty acid to pyruvate. These mitochondrial abnormalities were reversed by 8 weeks of oral carnitine supplementation, in concert with increased tissue efflux and urinary excretion of acetylcarnitine and improvement of whole body glucose tolerance. Acetylcarnitine is produced by the mitochondrial matrix enzyme, carnitine acetyltransferase (CrAT). A role for this enzyme in combating glucose intolerance was further supported by the finding that CrAT overexpression in primary human skeletal myocytes increased glucose uptake and attenuated lipid-induced suppression of glucose oxidation. These results implicate carnitine insufficiency and reduced CrAT activity as reversible components of the metabolic syndrome.

Quantification of training load during one-, two- and three-game week schedules in professional soccer players from the English Premier League: implications for carbohydrate periodisation

Liam Anderson, Patrick Orme, Rocco Di Michele +4 more · Journal of Sports Sciences · 2015 · 206 citations

Muscle glycogen is the predominant energy source for soccer match play, though its importance for soccer training (where lower loads are observed) is not well known. In an attempt to better inform carbohydrate (CHO) guidelines, we quantified training load in English Premier League soccer players (n = 12) during a one-, two- and three-game week schedule (weekly training frequency was four, four and two, respectively). In a one-game week, training load was progressively reduced (P < 0.05) in 3 days prior to match day (total distance = 5223 ± 406, 3097 ± 149 and 2912 ± 192 m for day 1, 2 and 3, respectively). Whilst daily training load and periodisation was similar in the one- and two-game weeks, total accumulative distance (inclusive of both match and training load) was higher in a two-game week (32.5 ± 4.1 km) versus one-game week (25.9 ± 2 km). In contrast, daily training total distance was lower in the three-game week (2422 ± 251 m) versus the one- and two-game weeks, though accumulative weekly distance was highest in this week (35.5 ± 2.4 km) and more time (P < 0.05) was spent in speed zones >14.4 km · h(-1) (14%, 18% and 23% in the one-, two- and three-game weeks, respectively). Considering that high CHO availability improves physical match performance but high CHO availability attenuates molecular pathways regulating training adaptation (especially considering the low daily customary loads reported here, e.g., 3-5 km per day), we suggest daily CHO intake should be periodised according to weekly training and match schedules.

High-Intensity Exercise Causes Greater Irisin Response Compared with Low-Intensity Exercise under Similar Energy Consumption

Yoshifumi Tsuchiya, Daisuke Ando, Kazushige Goto +3 more · The Tohoku Journal of Experimental Medicine · 2014 · 169 citations

Irisin is mainly released from skeletal muscle (myocytes) and promotes thermogenesis by browning of the white adipose tissue. Although exercise has been shown to increase irisin concentration in blood and myocytes via up-regulation peroxisome proliferator receptor γ coactivator-1α (PGC-1α) expression, the influence of exercise intensity on irisin secretion remains unclear. Therefore, we determined circulating irisin responses following a single bout of running at different intensities. Six sedentary males underwent treadmill running under two different conditions: a low-intensity (40% of VO2max) exercise trial (LIE) or a high-intensity (80% of VO2max) exercise trial (HIE). The exercises in LIE and HIE were lasted for 20 and 40 min, respectively. All subjects underwent the two trials on separate days, and a randomized cross-over design was used. Blood samples were collected before (Pre) and immediately after exercise, at 3, 6, and 19 h after exercise. Energy consumption during exercise did not significantly differ between the two trials. HIE significantly increased blood lactate and serum lactate dehydrogenase levels (P < 0.05). Compared with pre-exercise levels, the irisin concentrations were elevated at 6 h (18% increase) and 19 h (23% increase) after HIE, but significantly decreased after LIE. The relative irisin concentrations (compared with pre-exercise levels) were significantly greater in HIE than in LIE immediately after exercise, and at 6 and 19 h after exercise (P < 0.05). These findings suggest that irisin secretion after acute running exercise is affected by exercise intensity, independent of energy consumption.

Pharmacological but not physiological GDF15 suppresses feeding and the motivation to exercise

Anders B. Klein, Trine S. Nicolaisen, Niels Ørtenblad +22 more · Nature Communications · 2021 · 124 citations

Growing evidence supports that pharmacological application of growth differentiation factor 15 (GDF15) suppresses appetite but also promotes sickness-like behaviors in rodents via GDNF family receptor α-like (GFRAL)-dependent mechanisms. Conversely, the endogenous regulation of GDF15 and its physiological effects on energy homeostasis and behavior remain elusive. Here we show, in four independent human studies that prolonged endurance exercise increases circulating GDF15 to levels otherwise only observed in pathophysiological conditions. This exercise-induced increase can be recapitulated in mice and is accompanied by increased Gdf15 expression in the liver, skeletal muscle, and heart muscle. However, whereas pharmacological GDF15 inhibits appetite and suppresses voluntary running activity via GFRAL, the physiological induction of GDF15 by exercise does not. In summary, exercise-induced circulating GDF15 correlates with the duration of endurance exercise. Yet, higher GDF15 levels after exercise are not sufficient to evoke canonical pharmacological GDF15 effects on appetite or responsible for diminishing exercise motivation.

Effects of four different single exercise sessions on lipids, lipoproteins, and lipoprotein lipase

Michael A. Ferguson, Nathan L. Alderson, Stewart G. Trost +3 more · Journal of Applied Physiology · 1998 · 246 citations

The purpose of this study was to determine the threshold of exercise energy expenditure necessary to change blood lipid and lipoprotein concentrations and lipoprotein lipase activity (LPLA) in healthy, trained men. On different days, 11 men (age, 26.7 +/- 6.1 yr; body fat, 11.0 +/- 1.5%) completed four separate, randomly assigned, submaximal treadmill sessions at 70% maximal O2 consumption. During each session 800, 1,100, 1,300, or 1,500 kcal were expended. Compared with immediately before exercise, high-density lipoprotein cholesterol (HDL-C) concentration was significantly elevated 24 h after exercise (P < 0.05) in the 1,100-, 1,300-, and 1,500-kcal sessions. HDL-C concentration was also elevated (P < 0.05) immediately after and 48 h after exercise in the 1,500-kcal session. Compared with values 24 h before exercise, LPLA was significantly greater (P < 0.05) 24 h after exercise in the 1,100-, 1,300-, and 1,500-kcal sessions and remained elevated 48 h after exercise in the 1,500-kcal session. These data indicate that, in healthy, trained men, 1,100 kcal of energy expenditure are necessary to elicit increased HDL-C concentrations. These HDL-C changes coincided with increased LPLA.

Essential Role of Estrogen for Improvements in Vascular Endothelial Function With Endurance Exercise in Postmenopausal Women

Kerrie L. Moreau, Brian L. Stauffer, Wendy M. Kohrt +1 more · The Journal of Clinical Endocrinology & Metabolism · 2013 · 210 citations

OBJECTIVE: In contrast to age-matched men, endurance exercise training is not consistently associated with enhanced endothelial function in estrogen-deficient postmenopausal women. We determined whether endurance exercise training improves endothelial function in postmenopausal women treated with estrogen. In a substudy, we determined if oxidative stress is mechanistically linked to endothelial function adaptations to endurance exercise training. PARTICIPANTS AND DESIGN: Brachial artery flow-mediated dilation (FMD) was measured in 36 sedentary, estrogen-deficient postmenopausal women (45-65 y) at study entry (baseline), after 12 weeks of either placebo, oral (1 mg/d) estradiol, or transdermal estradiol (0.05 mg/d) (randomized), and after an additional 12 weeks of continued estradiol or placebo treatment with concurrent endurance exercise training. In subgroups of women, FMD also was measured during the infusion of ascorbic acid at baseline and following estradiol/placebo plus endurance exercise training, and in seven habitually endurance-trained estrogen-deficient controls. RESULTS: FMD increased in the estrogen-treated groups (both P < .01) after 12 weeks and remained unchanged in placebo. FMD further increased following 12 weeks of endurance exercise training in estrogen-treated (both P < .025), but not placebo-treated women (P = .55). In the substudy, baseline FMD was similar between sedentary and endurance-trained controls. Ascorbic acid increased FMD at baseline in sedentary women and endurance-trained controls, and following endurance exercise training in placebo-treated, but not in estrogen-treated women. CONCLUSIONS: Estrogen status appears to play an important modulatory role in improvements in endothelial function with endurance exercise training in postmenopausal women. The restored endurance exercise training adaptation in estrogen-treated postmenopausal women may be related to mitigation of oxidative stress.

Gut-training: the impact of two weeks repetitive gut-challenge during exercise on gastrointestinal status, glucose availability, fuel kinetics, and running performance

Ricardo J. S. Costa, Atlanta Miall, Anthony Khoo +4 more · Applied Physiology Nutrition and Metabolism · 2017 · 155 citations

) (trial × time: p = 0.015). No difference in oxidation rates, plasma I-FABP, and cortisol concentrations were observed between groups and trials. Distance test improved on CHO-S (5.2%) and CHO-F (4.3%) in GC2, but not on PLA (-2.1%) (trial × time: p = 0.009). Two weeks of gut-training with CHO-S and CHO-F improved gastrointestinal symptoms and running performance compared with PLA. CHO-S also reduced malabsorption and increased blood glucose availability during endurance running compared with PLA.

Four weeks of probiotic supplementation reduces GI symptoms during a marathon race

Jamie Pugh, S. Andy Sparks, Dominic A. Doran +6 more · European Journal of Applied Physiology · 2019 · 112 citations

PURPOSE: To evaluate the effects of probiotic supplementation on gastrointestinal (GI) symptoms, circulatory markers of GI permeability, damage, and markers of immune response during a marathon race. METHODS: Twenty-four recreational runners were randomly assigned to either supplement with a probiotic (PRO) capsule [25 billion CFU Lactobacillus acidophilus (CUL60 and CUL21), Bifidobacterium bifidum (CUL20), and Bifidobacterium animalis subs p. Lactis (CUL34)] or placebo (PLC) for 28 days prior to a marathon race. GI symptoms were recorded during the supplement period and during the race. Serum lactulose:rhamnose ratio, and plasma intestinal-fatty acid binding protein, sCD14, and cytokines were measured pre- and post-races. RESULTS: Prevalence of moderate GI symptoms reported were lower during the third and fourth weeks of the supplement period compared to the first and second weeks in PRO (p < 0.05) but not PLC (p > 0.05). During the marathon, GI symptom severity during the final third was significantly lower in PRO compared to PLC (p = 0.010). The lower symptom severity was associated with a significant difference in reduction of average speed from the first to the last third of the race between PLC (- 14.2 ± 5.8%) and PRO (- 7.9 ± 7.5%) (p = 0.04), although there was no difference in finish times between groups (p > 0.05). Circulatory measures increased to a similar extent between PRO and PLC (p > 0.05). CONCLUSION: Probiotics supplementation was associated with a lower incidence and severity of GI symptoms in marathon runners, although the exact mechanisms are yet to be elucidated. Reducing GI symptoms during marathon running may help maintain running pace during the latter stages of racing.

Energy Intake and Expenditure of Professional Soccer Players of the English Premier League: Evidence of Carbohydrate Periodization

Liam Anderson, Patrick Orme, Robert J. Naughton +11 more · International Journal of Sport Nutrition and Exercise Metabolism · 2017 · 146 citations

, Although players readily achieve current guidelines for daily protein and fat intake, data suggest that CHO intake on the day before and in recovery from match play was not in accordance with guidelines to promote muscle glycogen storage.

Dietary Nitrate and Physical Performance

Andrew M. Jones, Christopher Thompson, Lee J. Wylie +1 more · Annual Review of Nutrition · 2018 · 192 citations

cost of submaximal exercise and thereby improve endurance exercise performance and ( b) enhance skeletal muscle contractile function and thereby improve muscle power and sprint exercise performance. This review describes the physiological mechanisms potentially responsible for these effects, outlines the circumstances in which ergogenic effects are most likely to be evident, and discusses the effects of dietary nitrate supplementation on physical performance in a range of human populations.

Effect of caffeinated drinks on substrate metabolism, caffeine excretion, and performance

Éva Kovács, Jos H. C. H. Stegen, Fred Brouns · Journal of Applied Physiology · 1998 · 268 citations

The effect of addition of different dosages of caffeine (Caf) to a carbohydrate-electrolyte solution (CES) on metabolism, Caf excretion, and performance was examined. Subjects (n = 15) ingested 8 ml/kg of water placebo (Pla-W), 7% CES (Pla-CES), or 7% CES with 150, 225, and 320 mg/l Caf (CES-150, CES-225, and CES-320, respectively) during a warm-up protocol (20 min) and 3 ml/kg at one-third and two-thirds of a 1-h time trial. Performance was improved with Caf supplementation: 62.5 +/- 1.3, 61.5 +/- 1.1, 60.4 +/- 1.0, 58.9 +/- 1.0, and 58.9 +/- 1.2 min for Pla-W, Pla-CES, CES-150, CES-225, and CES-320, respectively. The postexercise urinary Caf concentration (range 1.3-2.5 microg/ml) was dose dependent and always far below the doping level of the International Olympic Committee (12 microg/ml) in all subjects. Sweat Caf excretion during exercise exceeded postexercise early-void urinary Caf excretion. Caffeinated CES did not enhance free fatty acid availability, ruling out the fact that performance improvement resulted from enhanced fat oxidation. It is concluded that addition of relatively low amounts of Caf to CES improves performance and that postexercise urinary Caf concentration remained low.

Toward a Common Understanding of Diet–Exercise Strategies to Manipulate Fuel Availability for Training and Competition Preparation in Endurance Sport

Louise M. Burke, John A. Hawley, Asker E. Jeukendrup +3 more · International Journal of Sport Nutrition and Exercise Metabolism · 2018 · 132 citations

From the breakthrough studies of dietary carbohydrate and exercise capacity in the 1960s through to the more recent studies of cellular signaling and the adaptive response to exercise in muscle, it has become apparent that manipulations of dietary fat and carbohydrate within training phases, or in the immediate preparation for competition, can profoundly alter the availability and utilization of these major fuels and, subsequently, the performance of endurance sport (events >30 min up to ∼24 hr). A variety of terms have emerged to describe new or nuanced versions of such exercise-diet strategies (e.g., train low, train high, low-carbohydrate high-fat diet, periodized carbohydrate diet). However, the nonuniform meanings of these terms have caused confusion and miscommunication, both in the popular press and among the scientific community. Sports scientists will continue to hold different views on optimal protocols of fuel support for training and competition in different endurance events. However, to promote collaboration and shared discussions, a commonly accepted and consistent terminology will help to strengthen hypotheses and experimental/experiential data around various strategies. We propose a series of definitions and explanations as a starting point for a more unified dialogue around acute and chronic manipulations of fat and carbohydrate in the athlete's diet, noting philosophies of approaches rather than a single/definitive macronutrient prescription. We also summarize some of the key questions that need to be tackled to help produce greater insight into this exciting area of sports nutrition research and practice.

The Effects of Nitrate Supplementation on Performance as a Function of Habitual Dietary Intake of Nitrates: A Randomized Controlled Trial of Elite Football Players

Matjaž Macuh, Nenad Kojić, Bojan Knap · Nutrients · 2023 · 7 citations

= 0.0104) in both the placebo and intervention groups. No effects of nitrate supplementation when baseline dietary nitrate intake was higher than 300 mg in the placebo group could be concluded due to the small sample size. Nitrate supplementation did not have a significant effect on perceived exertion. The daily nitrate intake of the participants was measured at 165 mg, with the majority of nitrates coming from nitrate-rich vegetables.

Influence of vitamin C supplementation on oxidative and immune changes after an ultramarathon

David C. Nieman, Dru A. Henson, Steve R. McAnulty +6 more · Journal of Applied Physiology · 2002 · 197 citations

The purpose of this randomized study was to measure the influence of vitamin C (n = 15 runners) compared with placebo (n = 13 runners) supplementation on oxidative and immune changes in runners competing in an ultramarathon race. During the 7-day period before the race and on race day, subjects ingested in randomized, double-blind fashion 1,500 mg/day vitamin C or placebo. On race day, blood samples were collected 1 h before race, after 32 km of running, and then again immediately after race. Subjects in both groups maintained an intensity of approximately 75% maximal heart rate throughout the ultramarathon race and ran a mean of 69 km (range: 48-80 km) in 9.8 h (range: 5-12 h). Plasma ascorbic acid was markedly higher in the vitamin C compared with placebo group prerace and rose more strongly in the vitamin C group during the race (postrace: 3.21 +/- 0.29 and 1.28 +/- 0.12 microg/100 microl, respectively, P < 0.001). No significant group or interaction effects were measured for lipid hydroperoxide, F2-isoprostane, immune cell counts, plasma interleukin (IL)-6, IL-10, IL-1-receptor antagonist, or IL-8 concentrations, or mitogen-stimulated lymphocyte proliferation and IL-2 and IFN-gamma production. These data indicate that vitamin C supplementation in carbohydrate-fed runners does not serve as a countermeasure to oxidative and immune changes during or after a competitive ultramarathon race.

Quercetin's Influence on Exercise Performance and Muscle Mitochondrial Biogenesis

David C. Nieman, Ashley S. Williams, R. Andrew Shanely +5 more · Medicine & Science in Sports & Exercise · 2010 · 196 citations

PURPOSE: To determine the influence of 2 wk of quercetin (Q; 1000 mg x d(-1)) compared with placebo (P) supplementation on exercise performance and skeletal muscle mitochondrial biogenesis in untrained, young adult males (N = 26, age = 20.2 +/- 0.4 yr, VO2max = 46.3 +/- 1.2 mL x kg(-1) x min(-1)). METHODS: Using a randomized, crossover design with a 2-wk washout period, subjects provided blood and muscle biopsy samples presupplementation and postsupplementation periods and were given 12-min time trials on 15% graded treadmills after 60 min of moderate exercise preloads at 60% VO2max. RESULTS: Plasma Q levels rose significantly in Q versus P during the 2-wk supplementation period (interaction P value <0.001). During the 12-min trial, the net change in distance achieved was significantly greater during Q (2.9%) compared with P (-1.2%; 29.5 +/- 11.5 vs -11.9 +/- 16.0 m, respectively, P = 0.038). Skeletal muscle messenger RNA expression tended to increase (range = 16-25%) during Q versus P for sirtuin 1 (interaction effect, P = 0.152), peroxisome proliferator-activated receptor gamma coactivator-1alpha (P = 0.192), cytochrome c oxidase (P = 0.081), and citrate synthase (P = 0.166). Muscle mitochondrial DNA (relative copy number per diploid nuclear genome) increased 140 +/- 154 (4.1%) with Q compared with -225 +/- 157 (6.0% decrease) with P (P = 0.098). CONCLUSIONS: In summary, 1000 mg x d(-1) Q versus P for 2 wk by untrained males was associated with a small but significant improvement in 12-min treadmill time trial performance and modest but insignificant increases in the relative copy number of mitochondrial DNA and messenger RNA levels of four genes related to mitochondrial biogenesis.

The effect of acute moderate-intensity exercise on the serum and fecal metabolomes and the gut microbiota of cross-country endurance athletes

Mariangela Tabone, Carlo Bressa, Jose Ángel García-Merino +5 more · Scientific Reports · 2021 · 94 citations

Physical exercise can produce changes in the microbiota, conferring health benefits through mechanisms that are not fully understood. We sought to determine the changes driven by exercise on the gut microbiota and on the serum and fecal metabolome using 16S rRNA gene analysis and untargeted metabolomics. A total of 85 serum and 12 fecal metabolites and six bacterial taxa (Romboutsia, Escherichia coli TOP498, Ruminococcaceae UCG-005, Blautia, Ruminiclostridium 9 and Clostridium phoceensis) were modified following a controlled acute exercise session. Among the bacterial taxa, Ruminiclostridium 9 was the most influenced by fecal and serum metabolites, as revealed by linear multivariate regression analysis. Exercise significantly increased the fecal ammonia content. Functional analysis revealed that alanine, aspartate and glutamate metabolism and the arginine and aminoacyl-tRNA biosynthesis pathways were the most relevant modified pathways in serum, whereas the phenylalanine, tyrosine and tryptophan biosynthesis pathway was the most relevant pathway modified in feces. Correlation analysis between fecal and serum metabolites suggested an exchange of metabolites between both compartments. Thus, the performance of a single exercise bout in cross-country non-professional athletes produces significant changes in the microbiota and in the serum and fecal metabolome, which may have health implications.

ISSN exercise & sports nutrition review update: research & recommendations

Chad M. Kerksick, Susan M. Kleiner, Jaci N Davis +12 more · UNC Libraries · 2019 · 92 citations

Abstract Background Sports nutrition is a constantly evolving field with hundreds of research papers published annually. In the year 2017 alone, 2082 articles were published under the key words ‘sport nutrition’. Consequently, staying current with the relevant literature is often difficult. Methods This paper is an ongoing update of the sports nutrition review article originally published as the lead paper to launch the Journal of the International Society of Sports Nutrition in 2004 and updated in 2010. It presents a well-referenced overview of the current state of the science related to optimization of training and performance enhancement through exercise training and nutrition. Notably, due to the accelerated pace and size at which the literature base in this research area grows, the topics discussed will focus on muscle hypertrophy and performance enhancement. As such, this paper provides an overview of: 1.) How ergogenic aids and dietary supplements are defined in terms of governmental regulation and oversight; 2.) How dietary supplements are legally regulated in the United States; 3.) How to evaluate the scientific merit of nutritional supplements; 4.) General nutritional strategies to optimize performance and enhance recovery; and, 5.) An overview of our current understanding of nutritional approaches to augment skeletal muscle hypertrophy and the potential ergogenic value of various dietary and supplemental approaches. Conclusions This updated review is to provide ISSN members and individuals interested in sports nutrition with information that can be implemented in educational, research or practical settings and serve as a foundational basis for determining the efficacy and safety of many common sport nutrition products and their ingredients.

Additive effects of beta-alanine and sodium bicarbonate on upper-body intermittent performance

Gabriel Cardial Tobias, Fabiana Braga Benatti, Vítor de Salles Painelli +6 more · Amino Acids · 2013 · 123 citations

We examined the isolated and combined effects of beta-alanine (BA) and sodium bicarbonate (SB) on high-intensity intermittent upper-body performance in judo and jiu-jitsu competitors. 37 athletes were assigned to one of four groups: (1) placebo (PL)+PL; (2) BA+PL; (3) PL+SB or (4) BA+SB. BA or dextrose (placebo) (6.4 g day⁻¹) was ingested for 4 weeks and 500 mg kg⁻¹ BM of SB or calcium carbonate (placebo) was ingested for 7 days during the 4th week. Before and after 4 weeks of supplementation, the athletes completed four 30-s upper-body Wingate tests, separated by 3 min. Blood lactate was determined at rest, immediately after and 5 min after the 4th exercise bout, with perceived exertion reported immediately after the 4th bout. BA and SB alone increased the total work done in +7 and 8 %, respectively. The co-ingestion resulted in an additive effect (+14 %, p < 0.05 vs. BA and SB alone). BA alone significantly improved mean power in the 2nd and 3rd bouts and tended to improve the 4th bout. SB alone significantly improved mean power in the 4th bout and tended to improve in the 2nd and 3rd bouts. BA+SB enhanced mean power in all four bouts. PL+PL did not elicit any alteration on mean and peak power. Post-exercise blood lactate increased with all treatments except with PL+PL. Only BA+SB resulted in lower ratings of perceived exertion (p = 0.05). Chronic BA and SB supplementation alone equally enhanced high-intensity intermittent upper-body performance in well-trained athletes. Combined BA and SB promoted a clear additive ergogenic effect.

Circulatory endotoxin concentration and cytokine profile in response to exertional-heat stress during a multi-stage ultra-marathon competition.

Samantha Gill, Ana Teixeira, Luís Rama +7 more · PubMed · 2015 · 120 citations

Exertional-heat stress has the potential to disturb intestinal integrity, leading to enhanced permeability of enteric pathogenic micro-organisms and associated clinical manifestations. The study aimed to determine the circulatory endotoxin concentration and cytokine profile of ultra-endurance runners (UER, n=19) and a control group (CON, n=12) during a five stage 230km ultra-marathon (mean ± SD: 27h38min ± 3h55min) conducted in hot and dry environmental conditions (30ºC to 40ºC and 31% to 40% relative humidity). Body mass and tympanic temperature were measured, and venous blood samples were taken before (pre-stage) and immediately after (post-stage) each stage of the ultra-marathon for the analysis of gram-negative bacterial endotoxin, C-reactive protein, cytokine profile (IL-6, IL-1β, TNF-α, IFN-γ, IL-10, and IL- 1ra), and plasma osmolality. Gastrointestinal symptoms and perceptive thermal tolerance rating were also monitored throughout competition. Mean exercise-induced body mass loss over the five stages ranged 1.0% to 2.5%. Pre- and poststage plasma osmolality in UER ranged277 to 282mOsmol/kg and 286 to 297 mOsmol/kg, respectively. Pre-stage concentrations of endotoxin (peak: 21% at Stage 5), C-reactive protein (889% at Stage 3), IL-6 (152% at Stage 2), IL-1β (95% at Stage 5), TNF-α (168% at Stage 5), IFN-γ (102% at Stage 5),IL-10 (1271% at Stage 3), and IL-1ra (106% at Stage 5) increased as the ultra-marathon progressed in UER; while no changes in CON were observed (except for IL-1β, 71% at Stage 5). Pre- to post-stage increases were observed for endotoxin (peak: 22% at Stage 3), C-reactive protein (25% at Stage 1), IL-6 (238% at Stage 1), IL-1β (64% at Stage 1), TNF-α (101% at Stage 1), IFN-γ (39% at Stage 1), IL-10 (1100% at Stage 1), and IL-1ra(207% at Stage 1) concentrations in UER. Multi-stage ultra-marathon competition in the heat resulted in a modest circulatory endotoxaemia accompanied by a pronounced pro-inflammatory cytokinaemia by post-Stage 1, both of which were sustained throughout competition at rest (pre-stage) and after stage completion. Compensatory anti-inflammatory responses and other external factors (i.e., training status, cooling strategies, heat acclimatization, nutrition and hydration) may have contributed towards limiting the extent of pro-inflammatory responses in the current scenario.

Influence of a Polyphenol-Enriched Protein Powder on Exercise-Induced Inflammation and Oxidative Stress in Athletes: A Randomized Trial Using a Metabolomics Approach

David C. Nieman, Nicholas D. Gillitt, Amy M. Knab +4 more · PLoS ONE · 2013 · 118 citations

OBJECTIVES: Polyphenol supplementation was tested as a countermeasure to inflammation and oxidative stress induced by 3-d intensified training. METHODS: Water soluble polyphenols from blueberry and green tea extracts were captured onto a polyphenol soy protein complex (PSPC). Subjects were recruited, and included 38 long-distance runners ages 19-45 years who regularly competed in road races. Runners successfully completing orientation and baseline testing (N = 35) were randomized to 40 g/d PSPC (N = 17) (2,136 mg/d gallic acid equivalents) or placebo (N = 18) for 17 d using double-blinded methods and a parallel group design, with a 3-d running period inserted at day 14 (2.5 h/d, 70% VO2max). Blood samples were collected pre- and post-14 d supplementation, and immediately and 14 h after the third day of running in subjects completing all aspects of the study (N = 16 PSPC, N = 15 placebo), and analyzed using a metabolomics platform with GC-MS and LC-MS. RESULTS: Metabolites characteristic of gut bacteria metabolism of polyphenols were increased with PSPC and 3 d running (e.g., hippurate, 4-hydroxyhippurate, 4-methylcatechol sulfate, 1.8-, 1.9-, 2.5-fold, respectively, P<0.05), an effect which persisted for 14-h post-exercise. Fatty acid oxidation and ketogenesis were induced by exercise in both groups, with more ketones at 14-h post-exercise in PSPC (3-hydroxybutyrate, 1.8-fold, P<0.05). Established biomarkers for inflammation (CRP, cytokines) and oxidative stress (protein carbonyls) did not differ between groups. CONCLUSIONS: PSPC supplementation over a 17-d period did not alter established biomarkers for inflammation and oxidative stress but was linked to an enhanced gut-derived phenolic signature and ketogenesis in runners during recovery from 3-d heavy exertion. TRIAL REGISTRATION: ClinicalTrials.gov, U.S. National Institutes of Health, identifier: NCT01775384.

The Impact of Moderate-Intensity Continuous or High-Intensity Interval Training on Adipogenesis and Browning of Subcutaneous Adipose Tissue in Obese Male Rats

Mousa Khalafi, Hamid Mohebbi, Michael Symonds +5 more · Nutrients · 2020 · 83 citations

This study compares the effect of two types of exercise training, i.e., moderate-intensity continuous training (MICT) or high-intensity interval training (HIIT) on the browning of subcutaneous white adipose tissue (scWAT) in obese male rats. Effects on fat composition, metabolites, and molecular markers of differentiation and energy expenditure were examined. Forty male Wistar rats were assigned to lean (n = 8) or obese (n = 32) groups and fed either a standard chow or high-fat obesogenic diet for 10 weeks. Eight lean and obese rats were then blood and tissue sampled, and the remaining obese animals were randomly allocated into sedentary, MICT, or HIIT (running on a treadmill 5 days/week) groups that were maintained for 12 weeks. Obesity increased plasma glucose and insulin and decreased irisin and FGF-21. In scWAT, this was accompanied with raised protein abundance of markers of adipocyte differentiation, i.e., C/EBP-α, C/EBP-β, and PPAR-γ, whereas brown fat-related genes, i.e., PRDM-16, AMPK/SIRT1/PGC-1α, were reduced as was UCP1 and markers of fatty acid transport, i.e., CD36 and CPT1. Exercise training increased protein expression of brown fat-related markers, i.e., PRDM-16, AMPK/SIRT1/PGC-1α, and UCP1, together with gene expression of fatty acid transport, i.e., CD36 and CPT1, but decreased markers of adipocyte differentiation, i.e., C/EBP-α, C/EBP-β, and plasma glucose. The majority of these adaptations were greater with HIIT compared to MICT. Our findings indicate that prolonged exercise training promotes the browning of white adipocytes, possibly through suppression of adipogenesis together with white to beige trans-differentiation and is dependent on the intensity of exercise.

A New Method for Non-Invasive Estimation of Human Muscle Fiber Type Composition

Audrey Baguet, Inge Everaert, Peter Hespel +3 more · PLoS ONE · 2011 · 112 citations

BACKGROUND: It has been established that excellence in sports with short and long exercise duration requires a high proportion of fast-twitch (FT) or type-II fibers and slow-twitch (ST) or type-I fibers, respectively. Until today, the muscle biopsy method is still accepted as gold standard to measure muscle fiber type composition. Because of its invasive nature and high sampling variance, it would be useful to develop a non-invasive alternative. METHODOLOGY: Eighty-three control subjects, 15 talented young track-and-field athletes, 51 elite athletes and 14 ex-athletes volunteered to participate in the current study. The carnosine content of all 163 subjects was measured in the gastrocnemius muscle by proton magnetic resonance spectroscopy ((1)H-MRS). Muscle biopsies for fiber typing were taken from 12 untrained males. PRINCIPAL FINDINGS: A significant positive correlation was found between muscle carnosine, measured by (1)H-MRS, and percentage area occupied by type II fibers. Explosive athletes had ∼30% higher carnosine levels compared to a reference population, whereas it was ∼20% lower than normal in typical endurance athletes. Similar results were found in young talents and ex-athletes. When active elite runners were ranked according to their best running distance, a negative sigmoidal curve was found between logarithm of running distance and muscle carnosine. CONCLUSIONS: Muscle carnosine content shows a good reflection of the disciplines of elite track-and-field athletes and is able to distinguish between individual track running distances. The differences between endurance and sprint muscle types is also observed in young talents and former athletes, suggesting this characteristic is genetically determined and can be applied in early talent identification. This quick method provides a valid alternative for the muscle biopsy method. In addition, this technique may also contribute to the diagnosis and monitoring of many conditions and diseases that are characterized by an altered muscle fiber type composition.

The Impact of Gastrointestinal Symptoms and Dermatological Injuries on Nutritional Intake and Hydration Status During Ultramarathon Events

Ricardo J. S. Costa, Rhiannon M. J. Snipe, Vera Camões‐Costa +2 more · Sports Medicine - Open · 2016 · 111 citations

BACKGROUND: Debilitating gastrointestinal symptoms (GIS) and dermatological injuries (DI) are common during and after endurance events and have been linked to performance decrements, event withdrawal, and issues requiring medical attention. The study aimed to determine whether GIS and DI affect food and fluid intake, and nutritional and hydration status, of ultramarathon runners during multi-stage (MSUM) and 24-h continuous (24 h) ultramarathons. METHODS: = 22) were recorded throughout both events and analysed by dietary analysis software. Body mass and urinary ketones were determined, and blood samples were taken, before and immediately after running. A medical log was used to monitor symptoms and injuries throughout both events. RESULTS: < 0.05) throughout the MSUM only. CONCLUSIONS: GIS during the MSUM, but not the 24 h, compromised nutritional intake. DI presence and severity also compromised nutrient intake during running and recovery in the MSUM.

Mouth rinse but not ingestion of a carbohydrate solution improves 1‐h cycle time trial performance

Andries Pottier, Jacques Bouckaert, W. Gilis +2 more · Scandinavian Journal of Medicine and Science in Sports · 2010 · 164 citations

The aim of the present study was to further explore the influence of ingestion and mouth rinse with a carbohydrate-electrolyte solution (CES) on the performance during a approximately 1 h high-intensity time trial on trained subjects. Subjects rinsed around the mouth or ingested a 6% isotonic CES or placebo (14 mL/kg body weight) before and throughout a time trial in which they had to accomplish a set amount of work (975+/-85 kJ) as quickly as possible. In the mouth rinse conditions, time to complete the test was shorter (P=0.02) with CES (61.7+/-5.1 min) than with placebo (64.1+/-6.5 min), whereas in the ingestion conditions, there was no difference between placebo (62.5+/-6.9 min) and CES (63.2+/-6.9 min). Although power output and lactate concentration during exercise were significantly higher when subjects rinsed their mouth with CES compared with placebo, the rating of perceived exertion values did not differ. Blood glucose concentration increased after ingestion of but not after mouth rinse with CES. The interesting finding of the present study is that rinsing the mouth with but not ingestion of CES resulted in improved performance.

Intake of a Ketone Ester Drink during Recovery from Exercise Promotes mTORC1 Signaling but Not Glycogen Resynthesis in Human Muscle

Tijs Vandoorne, Stefan De Smet, Monique Ramaekers +4 more · Frontiers in Physiology · 2017 · 107 citations

, we confirmed that ketone bodies potentiate the increase in mTORC1 activation and protein synthesis in leucine-stimulated myotubes. Whether, chronic oral KE intake during recovery from exercise can facilitate training-induced muscular adaptation and remodeling need to be further investigated.

Effects of sleeping with reduced carbohydrate availability on acute training responses

Stephen C. Lane, Donny M. Camera, David G. Lassiter +8 more · Journal of Applied Physiology · 2015 · 104 citations

We determined the effects of "periodized nutrition" on skeletal muscle and whole body responses to a bout of prolonged exercise the following morning. Seven cyclists completed two trials receiving isoenergetic diets differing in the timing of ingestion: they consumed either 8 g/kg body mass (BM) of carbohydrate (CHO) before undertaking an evening session of high-intensity training (HIT) and slept without eating (FASTED), or consumed 4 g/kg BM of CHO before HIT, then 4 g/kg BM of CHO before sleeping (FED). The next morning subjects completed 2 h of cycling (120SS) while overnight fasted. Muscle biopsies were taken on day 1 (D1) before and 2 h after HIT and on day 2 (D2) pre-, post-, and 4 h after 120SS. Muscle [glycogen] was higher in FED at all times post-HIT (P < 0.001). The cycling bouts increased PGC1α mRNA and PDK4 mRNA (P < 0.01) in both trials, with PDK4 mRNA being elevated to a greater extent in FASTED (P < 0.05). Resting phosphorylation of AMPK(Thr172), p38MAPK(Thr180/Tyr182), and p-ACC(Ser79) (D2) was greater in FASTED (P < 0.05). Fat oxidation during 120SS was higher in FASTED (P = 0.01), coinciding with increases in ACC(Ser79) and CPT1 as well as mRNA expression of CD36 and FABP3 (P < 0.05). Methylation on the gene promoter for COX4I1 and FABP3 increased 4 h after 120SS in both trials, whereas methylation of the PPARδ promoter increased only in FASTED. We provide evidence for shifts in DNA methylation that correspond with inverse changes in transcription for metabolically adaptive genes, although delaying postexercise feeding failed to augment markers of mitochondrial biogenesis.

Changes in lipoprotein subfractions during diet-induced and exercise-induced weight loss in moderately overweight men.

Paul T. Williams, Ronald M. Krauss, K M Vranizan +1 more · Circulation · 1990 · 207 citations

We studied separately the effects of weight loss by calorie restriction (dieting) and by calorie expenditure (primarily, running) on lipoprotein subfraction concentrations in sedentary, moderately overweight men assigned at random into three groups as follows: exercise without calorie restriction (n = 46), calorie restriction without exercise (n = 42), and control (n = 42). Plasma lipoprotein mass concentrations were measured by analytic ultracentrifugation for flotation rates (F0(1.20), S0f) within high density lipoprotein (HDL) (F0(1.20) 0-9), low density lipoprotein (LDL) (S0f 0-12), intermediate density lipoprotein (IDL) (S0f 12-20), and very low density lipoprotein (VLDL) (S0f 20-400) particle distributions. Particle diameter and flotation rate of the most abundant LDL species were determined by nondenaturing polyacrylamide gradient gel electrophoresis and analytic ultracentrifugation, respectively. During the 1-year trial, the exercisers ran (mean +/- SD) 15.6 +/- 9.1 km/wk, and the dieters ate 340 +/- 71 fewer kilocalories per day than at baseline. Total body weight was reduced significantly more in dieters (-7.2 +/- 4.1 kg) and exercisers (-4.0 +/- 3.9 kg) than controls (0.6 +/- 3.7 kg). As compared with mean changes in controls, the exercisers and dieters significantly increased HDL2 mass (48.6% and 47.1%, respectively), decreased VLDL mass (-23.9% and -25.5%), and increased LDL peak particle diameter (2.4 and 3.2 A). When adjusted to an equivalent change in body mass index by analysis of covariance, 1) exercise-induced and diet-induced weight loss produced comparable mean changes in the mass of small LDL and VLDL, and in LDL peak particle diameter; 2) the exercisers versus control group difference in HDL2 was attributed to the exercisers' reduced body mass index; and 3) HDL2 increased significantly less in dieters than in exercisers. In dieters, low calorie intake might mitigate the effects of weight loss on HDL2.