Effects of resistance training using elastic bands on muscle strength with or without a leucine supplement for 48 weeks in elderly patients with type 2 diabetes

This study investigated the effects of a home-based resistance training program using elastic bands, both with and without a daily leucine-rich amino acid supplement, on muscle strength, physical function, muscle mass, and cognitive function in elderly individuals with type 2 diabetes.

The interventions were:

**Resistance Exercise (R) group:** Performed daily bodyweight and elastic band resistance training at home.

**Resistance Exercise + Leucine Supplement (RL) group:** Performed the same daily resistance training as the R group and also took a daily leucine-rich amino acid supplement.

**Control (C) group:** Maintained their usual daily activities without any specific exercise or supplement intervention.

The primary outcome measure was:

**Knee extension strength:** A direct measure of quadriceps muscle strength, crucial for mobility and preventing falls.

Secondary outcome measures included:

**Grip strength:** A general indicator of overall muscle strength and frailty.

**Usual gait speed:** A measure of physical function and mobility.

**Muscle mass:** Measured by Dual-energy X-ray Absorptiometry (DEXA).

**Body mass index (BMI):** A measure of body weight relative to height.

**Fat mass:** Measured by DEXA.

**Cognitive function:** Assessed using the Mini-Mental State Examination (MMSE).

**Glycemic control:** Not explicitly listed as an outcome but mentioned as showing no changes.

The study included 60 elderly Japanese patients with type 2 diabetes.

**Sample size:** 60 patients initially, with 53 completing the study (18 in Control, 18 in Resistance Exercise, 17 in Resistance Exercise + Leucine).

**Population:** Patients with type 2 diabetes, aged 70 to 79 years, who had no dementia (MMSE score of 24 or higher).

**Exclusion criteria:** Patients with diabetic ketosis, proliferative diabetic retinopathy, chronic kidney disease, a history of ischemic heart disease, musculoskeletal disease, acute infection, diabetic foot, severe diabetic autonomic neuropathy, malignancy, or those currently taking certain diabetes medications (SGLT2 inhibitors, pioglitazone, GLP-1 receptor agonists) due to their effects on body weight.

**Setting:** Recruited from the outpatient clinic of St. Marianna University Hospital in Kawasaki, Japan.

**Baseline characteristics (for the 53 completers):**

* Mean age: 72.9 ± 2.4 years.

* Gender: 47% women (25 women, 28 men).

* Mean BMI: 23.7 ± 3.8 kg/m².

* Mean MMSE score: 28.7 ± 1.5.

* No significant differences in baseline characteristics were found among the three groups.

**Knee extension strength:** Measured twice using handheld dynamometry (μTas MF-01, ANIMA corp., Tokyo, Japan) by trained physical therapists. The average of two consecutive measurements was recorded. This method directly assesses the force generated by the quadriceps muscles.

**Grip strength:** Measured using a hand dynamometer (JAMAR® Hydraulic Hand Dynamometer, Sammons Preston Inc., Canada) with patients in a standing position, arms straight at their sides. This is a common, reliable measure of overall upper body strength.

**Usual gait speed:** Measured by a researcher using a stopwatch over a 6-meter distance. This is a simple, practical assessment of functional mobility.

**Bodyweight, lean body mass, and fat mass:** Measured using Dual-energy X-ray Absorptiometry (DEXA) (Lunar PRODIGY Advance, GE Healthcare Japan Corp., Tokyo, Japan). DEXA is a highly accurate method for assessing body composition, distinguishing between bone, lean tissue (muscle), and fat.

**Body Mass Index (BMI):** Calculated as body weight (kg) divided by height squared (m²).

**Cognitive function:** Assessed using the Mini-Mental State Examination (MMSE). The MMSE is a widely used 30-point questionnaire to screen for cognitive impairment, covering orientation, attention, memory, language, and visuospatial skills. A score of 24 or higher was an inclusion criterion, indicating no dementia.

**Exercise adherence:** Participants self-reported daily whether they performed the instructed exercise program. This relies on participant honesty and memory.

This was a **prospective, single-center, randomized, 48-week, 3-group, open trial** conducted in Kawasaki, Japan.

**Study Design:**

* **Randomized Controlled Trial (RCT):** Participants were randomly assigned to one of three groups (Control, Resistance Exercise, Resistance Exercise + Leucine Supplement). This is the gold standard for establishing cause-and-effect relationships because randomization helps ensure that, on average, the groups are similar in all characteristics (known and unknown) at the start of the study, except for the intervention they receive. This minimizes confounding variables.

* **Single-center:** The study was conducted at one hospital. While this can ensure consistency in procedures, it may limit the generalizability of findings to other populations or settings.

* **48-week duration:** This is a relatively long intervention period, allowing for the observation of sustained effects and adaptations to exercise and supplementation over time, which is important for muscle and cognitive changes.

* **3-group design:** Allowed for direct comparison of resistance training alone, resistance training plus supplement, and no intervention.

* **Open trial:** This means that neither the participants nor the researchers (including those measuring outcomes) were blinded to the group assignments.

**Randomisation:**

* 60 eligible patients were randomly allocated to one of the three groups (1:1:1 ratio) using the **minimization method**, taking into account gender.

* **Minimization** is a dynamic allocation method that aims to keep baseline characteristics (like gender in this case) balanced across groups as participants are recruited. This helps ensure that any observed differences are more likely due to the intervention rather than pre-existing imbalances.

**Blinding:**

* The study was an **"open trial,"** meaning there was no blinding. Participants knew which group they were in (e.g., if they were exercising or taking a supplement). The researchers and physical therapists who measured outcomes also knew the group assignments.

* **Why this design matters:** Lack of blinding can introduce **performance bias** (participants might change their behavior or effort based on their group knowledge) and **detection bias** (researchers measuring outcomes might consciously or unconsciously influence results if they know who received which intervention). For objective measures like knee extension strength measured by dynamometry, detection bias might be less pronounced than for subjective measures, but it's still a potential weakness. For self-reported exercise adherence, it's a significant concern.

**Washout Periods:** Not applicable, as this was a parallel-group RCT where each group received a distinct intervention (or none) for the entire study duration, rather than switching interventions.

**Intervention Details:**

* **Resistance Training (R and RL groups):** Participants were instructed to perform daily bodyweight and elastic band exercises for about 15 minutes for 48 weeks.

* **Elastic bands:** THERABAND® bands of varying resistance (yellow, red, green, blue, black, with resistance from 1.3 kg to 3.3 kg at 100% elongation).

* **Progression:** Participants started with a specific band color based on gender and prior exercise habits. When they could easily complete 20 repetitions, they were instructed to change to the next color (higher resistance).

* **Exercises:**

* **Upper limb (with elastic bands):** Tube fly, Front raise, Hammer curl.

* **Lower limb (with elastic band and bodyweight):** Leg extension (with band), Calf raise (bodyweight), Squat (bodyweight).

* **Repetitions:** 20 repetitions for each exercise, every day.

* **Adherence:** Self-reported daily. Mean adherence rate was 87.8% in the R group and 87.5% in the RL group.

* **Leucine Supplement (RL group):** Participants took 6 g of a leucine-rich amino acid supplement (Amino L40®, AJINOMOTO Co., Inc.) daily, divided into two doses (three hours after breakfast and lunch) for 48 weeks. Each 6g dose contained 1.2g leucine and 1.8g other amino acids.

**Statistical Approach:**

* **Sample Size Calculation:** Based on a previous study, a sample size of 16 patients per group was calculated to detect a significant mean change with an effect size of 10 Nm (for knee extension strength), assuming α = 0.05 and power = 0.80. They recruited 20 cases per group to account for potential dropouts.

* **Within-group changes:** Paired t-tests were used to evaluate changes from baseline to 48 weeks within each group.

* **Between-group differences (Primary Outcome):** A one-way Analysis