Changes in human muscle protein synthesis after resistance exercise.
Level 3 - non-randomized controlled study
Non-randomized controlled physiological study using within-subject contralateral limb controls across two post-exercise cohorts.
PubMed 1280254 · doi:10.1152/jappl.1992.73.4.1383
What was done
Twelve male subjects performed heavy resistance exercise with the elbow flexors of one arm while the opposite arm served as an unexercised control. Subjects were allocated to two groups of six: Group A was assessed at 4 hours post-exercise and Group B at 24 hours post-exercise. Muscle protein synthesis (MPS) in biceps brachii biopsy samples was measured by the incorporation of L-[1-13C]leucine. Total RNA capacity and RNA activity were also assessed to determine translational versus transcriptional contributions.
What was found
MPS was significantly elevated in the exercised biceps compared to the control arm at 4 hours (Group A: 0.1007 ± 0.0330%/h vs. 0.067 ± 0.0204%/h) and at 24 hours post-exercise (Group B: 0.0944 ± 0.0363%/h vs. 0.0452 ± 0.0126%/h). RNA capacity did not differ between exercised and control arms in either group. RNA activity was significantly increased in the exercised arm at 4 hours (0.19 ± 0.10 vs. 0.12 ± 0.05 µg protein·h⁻¹·µg⁻¹ total RNA) and at 24 hours (0.18 ± 0.06 vs. 0.08 ± 0.02 µg protein·h⁻¹·µg⁻¹ total RNA).
Why it matters
This paper demonstrates that a single bout of resistance exercise elevates human muscle protein synthesis for up to 24 hours, primarily driven by increases in translational activity rather than increased RNA capacity.
Limits
The sample size is very small (n = 12 total, 6 per time group) and restricted exclusively to males. Measurements were taken at only two discrete time points (4 and 24 hours), and longer-term time courses or protein breakdown rates were not reported.
Cited by
- supports The muscle protein synthetic response to resistance training lasts for a time course of roughly 48 hours.