Acute resistance exercise augments integrative myofibrillar protein synthesis.
Level 2 - randomized trial
Controlled within-subject experimental trial in humans
PubMed 21864869 · doi:10.1016/j.metabol.2011.07.001
What was done
Twelve healthy young men were studied over 24 hours under controlled total energy and macronutrient intake. Participants performed an acute bout of exhaustive unilateral resistance exercise (5 sets to volitional failure at 85% 1-repetition maximum of leg press and knee extension), with one leg exercised (EX) and the contralateral leg serving as a resting control (CON). Deuterated water (2H2O, 70%) was administered to measure integrative mixed muscle and myofibrillar fractional synthesis rates (FSR). Vastus lateralis muscle biopsies were obtained from both legs 16 hours post-exercise.
What was found
Body water 2H-labeling was 0.32 ± 0.01 mole percent excess across the experiment. Integrative mixed muscle FSR (%/h) was similar between legs (CON: 0.76% ± 0.08% vs EX: 0.69% ± 0.06%). In contrast, myofibrillar FSR was significantly increased by resistance exercise (EX: 0.94% ± 0.16% vs CON: 0.75% ± 0.08%; P < .05).
Why it matters
Using heavy water tracer methodology, this study demonstrates that acute high-intensity resistance exercise selectively stimulates cumulative 24-hour myofibrillar protein synthesis in untrained individuals, an effect that is missed when evaluating whole mixed muscle protein synthesis.
Limits
The study is limited by a small sample size (n = 12) restricted entirely to healthy young men. It evaluated only a single acute exercise bout over 24 hours, and longer-term adaptations or training effects were not measured.
Cited by
- supports The human body remains highly anabolic for at least 24 hours following a resistance training workout.