Muscle Damage
Conditions
Keywords
Tactical Athletes, Protein Distribution, Leucine Supplementation, Lean Body Mass, Muscle Protein Synthesis, Resistance Training
Brief summary
This randomized controlled trial will examine the effects of within-day protein distribution and leucine supplementation on body composition, physical performance, and biomarkers of muscle damage in tactical athletes during an 8-week intensive training program. Sixty-nine healthy male participants (18-35 years) enrolled in a Ministry of Defense training course will be randomly assigned to one of three iso-caloric dietary groups providing 1.6 g/kg/day of protein: (1) evenly distributed protein across three meals (EVEN), (2) a 16-hour daily protein fasting pattern with protein concentrated at lunch and dinner (FAST), or (3) the same fasting pattern with 5 g leucine supplementation at breakfast (FAST-RESCUE). Primary outcomes include changes in lean body mass. Secondary outcomes include strength, anaerobic performance, and biochemical markers of muscle damage, including urinary titin N-terminal fragment (UTF). Assessments will be conducted at baseline, Week 5, and Week 8.
Detailed description
This study is an 8-week, three-arm, parallel-group randomized controlled trial conducted in healthy male tactical trainees (18-35 years) enrolled in a Ministry of Defense training program. Participants will undergo a high-volume concurrent training regimen exceeding 30 hours per week, including resistance training, load carriage, aerobic conditioning, and combat-based drills. Participants (n=69) will be randomized in a 1:1:1 ratio to one of three iso-caloric dietary interventions providing 1.6 g/kg/day of protein: 1. EVEN: Protein evenly distributed across three daily meals (08:00, 13:00, 18:00). 2. FAST: Skewed protein distribution with a 16-hour protein-free window (21:00-13:00), omitting protein at breakfast and concentrating intake at lunch and dinner. 3. FAST-RESCUE: Identical to FAST, with addition of 5 g free-form leucine consumed at breakfast. Energy intake will be individualized based on measured resting metabolic rate and estimated physical activity level. Dietary adherence will be monitored daily using a mobile application and weekly dietitian supervision. Primary Outcome: \- Change in lean body mass measured by bioelectrical impedance analysis from baseline to Week 8. Secondary Outcomes: * Maximal strength (isometric mid-thigh pull, maximal voluntary contraction, handgrip strength) * Anaerobic performance (Wingate test, countermovement jump) * Serum biomarkers (creatine kinase, urea, testosterone, inflammatory markers) * Urinary titin N-terminal fragment to creatinine ratio (UTF/Cr) as a marker of myofibrillar damage Assessments will be performed at baseline, Week 5, and Week 8. Data will be analyzed according to the intention-to-treat principle using linear mixed models to evaluate Group × Time interactions.
Interventions
DIETARY_SUPPLEMENTL-leucine supplementation
Participants ingest 5 g free-form L-leucine at breakfast (\~08:00) daily for 8 weeks. Leucine is provided as unflavored, pharmaceutical-grade instantized powder, reconstituted in water and consumed at the protein-free breakfast meal.
BEHAVIORALEven Protein Distribution
Iso-caloric diet providing 1.6 g/kg/day protein evenly distributed across three daily meals for 8 weeks.
BEHAVIORALSkewed Protein Distribution (16-hour Protein-Fasting Window)
Iso-caloric diet providing 1.6 g/kg/day protein with protein omitted at breakfast and concentrated at lunch and dinner, creating a 16-hour daily protein-free window for 8 weeks.
Sponsors
Tel Aviv University
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
PREVENTION
Masking
NONE
Masking description
Due to the nature of the dietary intervention and differences in meal timing, participants and study personnel responsible for dietary supervision are not blinded to group allocation. Laboratory analyses of biochemical outcomes may be performed without knowledge of group assignment.
Intervention model description
This is a three-arm, parallel-group randomized controlled trial. Participants will be randomly assigned in a 1:1:1 ratio to one of three dietary intervention groups (EVEN, FAST, FAST-RESCUE) for 8 weeks during an intensive tactical training program. Each group will follow a distinct protein distribution strategy while maintaining identical total daily protein intake (1.6 g/kg/day) and iso-caloric energy intake.
Eligibility
Sex/Gender
MALE
Age
18 Years to 35 Years
Healthy volunteers
Yes
Inclusion criteria
* Male participants aged 18-35 years * Enrolled in an active Ministry of Defense tactical training program * Physically active and medically cleared to participate in intensive training * Willing and able to comply with the dietary intervention and training protocol * Provide written informed consent prior to participation
Exclusion criteria
* Musculoskeletal or neuromuscular injury or impairment limiting participation in exercise training * Cardiopulmonary disease (including recent myocardial infarction or unstable angina) * History of cancer, diabetes, thyroid disease, hypertension, or chronic renal failure * Cognitive impairment affecting ability to provide informed consent * Use of medications that may affect metabolism, muscle physiology, or exercise performance * Known allergy or intolerance to study dietary components or leucine supplementation * Non-compliance with study protocol requirements
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Change in Lean Body Mass (LBM) | Baseline (Week 1) to Week 8 | Lean body mass (kg) assessed by multi-frequency bioelectrical impedance analysis (BIA) using the SECA mBCA 515. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Change in Fat Mass Percentage | Baseline (Week 1), Week 5, and Week 8 | Fat mass percentage (%) assessed by multi-frequency bioelectrical impedance analysis (SECA mBCA 515). |
| Change in Fat-Free Mass (FFM) | Baseline (Week 1), Week 5, and Week 8 | Fat-free mass (kg) assessed by multi-frequency bioelectrical impedance analysis (SECA mBCA 515). |
| Change in Skeletal Muscle Mass (SMM) | Baseline (Week 1), Week 5, and Week 8 | Skeletal muscle mass (kg) assessed by multi-frequency bioelectrical impedance analysis (SECA mBCA 515). |
| Change in Maximal Strength - Isometric Mid-Thigh Pull (IMTP) | Baseline (Week 1), Week 5, and Week 8 | Maximal force during IMTP measured using a force plate system (k-Delta). Best of two trials recorded. |
| Change in Maximal Voluntary Isometric Contraction (MVC) | Baseline (Week 1), Week 5, and Week 8 | Knee extension MVC force measured using a strain gauge system. Best of trials recorded per protocol procedures. |
| Change in Handgrip Strength | Baseline (Week 1), Week 5, and Week 8 | Handgrip strength measured with a handgrip dynamometer; best value recorded. |
| Change in Countermovement Jump (CMJ) Performance | Baseline (Week 1), Week 5, and Week 8 | Jump height measured via force plate system; best of two trials recorded. |
| Change in Peak Power Output (Wingate Test) | Baseline (Week 1), Week 5, and Week 8 | Peak power output (W) during a 30-second Wingate Anaerobic Test performed on a cycle ergometer. |
| Change in Mean Power Output (Wingate Test) | Baseline (Week 1), Week 5, and Week 8 | Mean power output (W) during a 30-second Wingate Anaerobic Test performed on a cycle ergometer. |
| Change in Urinary Titin N-terminal Fragment to Creatinine Ratio (UTF/Cr) | Baseline (Week 1) and Week 5 | Urinary titin N-terminal fragment (UTF) normalized to creatinine as a biomarker of myofibrillar damage, assessed from morning urine samples using ELISA methods described in the protocol. |
| Change in Serum Creatine Kinase (CK) | Baseline (Week 1), Week 5, and Week 8 | Serum CK concentration measured from blood samples as a marker of muscle damage. |
| Change in Serum Urea (Blood Urea Nitrogen, BUN) | Baseline (Week 1), Week 5, and Week 8 | Serum urea concentration (mg/dL or mmol/L) measured from venous blood samples. |
| Change in Total Testosterone | Baseline (Week 1), Week 5, and Week 8 | Serum total testosterone measured from blood samples. |
| Change in C-Reactive Protein (CRP) | Baseline (Week 1), Week 5, and Week 8 | Serum C-reactive protein concentration (mg/L) measured from venous blood samples. |
| Change in Tumor Necrosis Factor-alpha (TNF-α) | Baseline (Week 1), Week 5, and Week 8 | Serum TNF-α concentration (pg/mL) measured from venous blood samples. |
| Change in Interleukin-6 (IL-6) | Baseline (Week 1), Week 5, and Week 8 | Serum IL-6 concentration (pg/mL) measured from venous blood samples. |
| Change in Resting Metabolic Rate (RMR) | Baseline (Week 1) and Week 8 | Resting metabolic rate (kcal/day) assessed by indirect calorimetry using a metabolic cart under standardized fasting conditions. |
Contacts
CONTACTLien Bruck
PRINCIPAL_INVESTIGATORYftach Gepner, PhD
Tel Aviv University
Outcome results
None listed