Skeletal Muscle Protein Synthetic Response to Amino Acid and Peptides

• Resistance Exercise (Behavioral): Prior to protein consumption participants will perform an acute bout of resistance exercise. They will warm up with two sets of 10 repetitions at 35-75% working load respectively, then perform four working sets of 10-12 repetitions at 65-70% of 1-RM. 1 min, 30 sec rest periods will be implemented between each set.
• No Resistance Exercise (Behavioral): Participants allocated to this group will not perform exercise prior to the administration of the nutritional intervention. Participants will remain at rest throughout the trial.
• Leucine (Dietary supplement): Participants will be given 2g of leucine dissolved in 250mL of water. Drink will be consumed immediately after exercise or equivalent time point for non-exercise group.
• Dileucine (Dietary supplement): Participants will be given 2g of dileucine dissolved in 250mL of water. Drink will be consumed immediately after exercise or equivalent time point for non-exercise group.

Primary outcomes

• Fractional Synthetic Rate of Mixed Muscle Proteins [Postabsorptive for 3.5 hours, Postprandial for 3 hours.]: Mixed muscle protein synthesis rates will be assessed during the 3.5hr Postabsorptive period (e.g. non-fed state) and the 3hr postprandial period (e.g. fed state) for both experimental interventions (e.g. leucine and leucine peptide). This will allow us to assess the change in fractional synthetic rate from the Postabsorptive period to the postprandial period.
• Fractional Synthetic Rate of Myofibrillar Proteins [Postabsorptive for 3.5 hours, Postprandial for 3 hours.]: Myofibrillar muscle protein synthesis rates will be assessed during the 3.5hr Postabsorptive period (e.g. non-fed state) and the 3hr postprandial period (e.g. fed state) for both experimental interventions (e.g. leucine and leucine peptide). This will allow us to assess the change in fractional synthetic rate from the Postabsorptive period to the postprandial period.
• Fractional Breakdown Rate of Mixed Muscle Proteins [Postprandial for 1 hour]: Mixed muscle protein breakdown rates will be assessed during the first hour of the postprandial period (e.g. fed state) for both experimental interventions (e.g. leucine and leucine peptide). This will allow us to assess the change in fractional breakdown rate for each respective experimental intervention.

Secondary outcomes

• Phosphorylation of muscle anabolic signaling [Baseline, immediately after ingestion of leucine/leucine peptides, and 3 hours after ingestion of leucine/leucine peptides]: Phosphorylation of anabolic signaling pathways will be assessed in the fasted state and after the ingestion of the experimental interventions.

Sex: All, ages: 18 Years to 35 Years, accepts healthy volunteers

Inclusion Criteria:

* Recreationally-active adults: ≥ 30 min of physical activity at moderate intensity ≥ 3 times per week
* Ages: 18-35 years old
* English fluency

Exclusion Criteria:

* Tobacco, nicotine (patch/gum) use (previous 6 mo)
* Alcohol consumption >10 drinks per week
* Metabolic disorders (e.g., Metabolic Syndrome, Diabetes, thyroid diseases)
* Cardiovascular disease, arrhythmias
* Hypogonadism
* Asthma
* History of uncontrolled hypertension
* Orthopedic injury/surgery (within 1 yr)
* Hepatorenal, musculoskeletal, autoimmune, or neurological disease
* History of neuromuscular problems
* Previous participation in amino acid tracer studies
* Predisposition to hypertrophic scarring or keloid formation
* Consumption of ergogenic-levels of dietary supplements that may affect muscle mass (e.g., creatine, HMB), insulin-like substances, or anabolic/catabolic pro-hormones (e.g., DHEA) within 6 weeks prior to participation
* Consumption of thyroid, androgenic, or other medications known to affect endocrine function
* Consumption of medications known to affect protein metabolism (e.g., prescription-strength corticosteroids, non-steroidal anti-inflammatories, or acne medication)
* Currently pregnant

• Informed Consent Form (PDF, 2019-06-20)

• Nicholas A. Burd, Ph.D., Principal investigator, University of Illinois at Urbana-Champaign