Dileucine and Resistance Training Adaptations

The study will be conducted using a randomized, double-blind approach with individuals being provided daily 2-gram doses of leucine, 2-gram doses of dileucine, or a placebo. Daily blinded supplementation will occur each day for a 10-week period of time while completing a heavy resistance training program. Participants follow the resistance training program for a total of 10 weeks. To compare the efficacy of leucine in form of amino acid or dipeptide supplementation on resistance training adaptations, changes in fat-free, lean, and fat mass will be determined using a 4-compartment body composition model. Skeletal muscle cross-sectional area will be assessed using ultrasound. Maximal strength, muscular endurance, and power will also be assessed. Participants will be required to provide weekly compliance and complete one supervised workout per week. After 2, 6, and 10 weeks of following the supplementation and resistance training regimens, participants will return to the laboratory to complete testing bouts consisting of identical assessments of body composition, muscular strength, muscular endurance, lower-body power, and anaerobic capacity. Adverse events related to each supplementation group will be recorded and assessed.

• Placebo (Dietary supplement): Participants will supplement daily for 10 weeks with 2 grams rice flower placebo in capsule form. On training days, participants will consume their assigned supplement within 60 minutes of completing their workout. On non-training days, participants will consume their assigned supplement with their first meal of the day. All doses will be consumed with 8-12 ounces of water.
• Leucine (Dietary supplement): Participants will supplement daily for 10 weeks with 2 grams leucine in capsule form. On training days, participants will consume their assigned supplement within 60 minutes of completing their workout. On non-training days, participants will consume their assigned supplement with their first meal of the day. All doses will be consumed with 8-12 ounces of water.
• Dileucine (Dietary supplement): Participants will supplement daily for 10 weeks with 2 grams dileucine (RAMPS, Ingenious Ingredients, TX, USA) in capsule form. On training days, participants will consume their assigned supplement within 60 minutes of completing their workout. On non-training days, participants will consume their assigned supplement with their first meal of the day. All doses will be consumed with 8-12 ounces of water.

Primary outcomes

• Fat-Free Mass [10 weeks]: Fat-free mass will be determined via Dual-Energy X-Ray Absorptiometry
• Leg Press 1RM [10 weeks]: Leg Press 1RM will be measured using the leg press (lower-body) exercise.
• Bench Press 1RM [10 weeks]: Bench Press 1RM will be measured using the bench press (upper-body) exercise.
• Maximal Isometric Mid-Thigh Pull Force Production [10 weeks]: Maximal Isometric Mid-Thigh Pull Force Production will be measured using an isometric mid-thigh pull test

Secondary outcomes

• Fat Mass [10 weeks]: Fat mass will be determined via Dual-Energy X-Ray Absorptiometry
• Lean mass [10 weeks]: Lean mass will be determined via Dual-Energy X-Ray Absorptiometry
• % Body Fat [10 weeks]: % Body Fat will be determined via Dual-Energy X-Ray Absorptiometry
• Total body water [10 weeks]: Total Body Water will be determined via bioelectrical impedance analysis
• Extracellular Body Water [10 weeks]: Extracellular Body Water will be determined via bioelectrical impedance analysis
• Intracellular Body Water [10 weeks]: Intracellular Body Water will be determined via bioelectrical impedance analysis
• Skeletal muscle cross-sectional area [10 weeks]: Skeletal muscle cross-sectional area will be measured using ultrasound measurements of the participants thigh muscles.
• Bench Press Repetitions to Fatigue [10 weeks]: Bench Press repetitions to fatigue will be measured using the bench press (upper-body) exercises on four separate occasions (visits 2, 3, 4, and 5). To complete this assessment, study participants will use a load that corresponds to 80% of their Visit 2 1RM for bench press exercise and will be instructed to complete as many repetitions as they can until failure for one set of each exercise. Failure will be defined as resting for more than two seconds throughout any point on the exercise set or technique failure.
• Leg Press Repetitions to Fatigue [10 weeks]: Leg Press repetitions to fatigue will be measured using the leg press (lower-body) exercises on four separate occasions (visits 2, 3, 4, and 5). To complete this assessment, study participants will use a load that corresponds to 80% of their Visit 2 1RM for leg press exercise and will be instructed to complete as many repetitions as they can until failure for one set of each exercise. Failure will be defined as resting for more than two seconds throughout any point on the exercise set or technique failure.
• Peak Anaerobic Power [10 weeks]: Peak Anaerobic Power will be measured using a Wingate Anaerobic Test lasting 30-seconds at a load set to 7.5% of week 0 body mass
• Mean Anaerobic Power [10 weeks]: Mean Anaerobic Power will be measured using a Wingate Anaerobic Test lasting 30-seconds at a load set to 7.5% of week 0 body mass
• Rate of Fatigue [10 weeks]: Rate of Fatigue will be measured using a Wingate Anaerobic Test lasting 30-seconds at a load set to 7.5% of week 0 body mass
• Maximal Concentric Rate of Force Development [10 weeks]: Maximal concentric rate of force development will be measured using a countermovement jump performed on a force plate

Sex: Male, ages: 18 Years to 39 Years, accepts healthy volunteers

Inclusion Criteria:

* Male
* Between the ages of 18-39 years of age
* Currently participating in resistance training exercise

Exclusion Criteria:

* Female
* Participants who are determined to not be weight stable defined as week 0 and week 2 body mass levels deviating by 3% or more.
* Any individual who is currently being treated for or diagnosed with a cardiac, respiratory, circulatory, musculoskeletal, metabolic, immune, autoimmune, psychiatric, hematological, neurological or endocrinological disorder or disease.
* Body mass index > 25 kg/m2. Individuals with a body mass index greater than 25 kg/m2, but a body fat percentage less than 25% fat will be accepted into the study
* Individuals who present with any previous injury or illness that would prevent them from appropriately completing all exercise lifts.
* Participants who are not able to fit onto the DEXA table will not be able to participate in the research due to size restrictions of the equipment. This typically includes individuals exceeding 400 pounds or those greater than 6'4".
* Those individuals with less than 12 months of structured resistance training experience will be excluded from the study.
* Individuals whose maximal relative upper body strength is below 1.0 will be excluded.
* Individuals whose maximal relative lower body strength is below 1.5 will be excluded.
* All participants who DO NOT abstain from taking any additional forms of nutritional supplementation deemed to be ergogenic or that will impact resistance training adaptations (pre-workouts, creatine, beta-alanine, etc.) for four weeks prior to beginning this study and for the entire duration of the study.
* Individuals who are currently using or have used within the past 12 months anabolic-androgenic steroids.

• Results publication: Hagele AM, Krieger JM, Gaige CJ, Holley KF, Gross KN, Iannotti JM, Allen LE, Sutton PJ, Orr LS, Mumford PW, Purpura M, Jager R, Kerksick CM. Dileucine ingestion, but not leucine, increases lower body strength and performance following resistance training: A double-blind, randomized, placebo-controlled trial. PLoS One. 2024 Dec 31;19(12):e0312997. doi: 10.1371/journal.pone.0312997. eCollection 2024. PMID 39739679

• Chad M Kerksick, PhD, Principal investigator, Lindenwood University