Differential effects of resistance and endurance exercise in the fed state on signalling molecule phosphorylation and protein synthesis in human muscle.
Level 3 - non-randomized controlled study
Non-randomized or unspecified-allocation interventional exercise training study in humans
PubMed 18556367 · doi:10.1113/jphysiol.2008.153916
What was done
In young healthy men in the fed state, researchers measured myofibrillar and mitochondrial protein synthesis rates alongside Akt-mTOR-p70S6K signaling pathway activation at rest and following an acute bout of resistance exercise (RE) or endurance exercise (EE). Measurements were taken in the untrained state and repeated after 10 weeks of dedicated RE or EE training.
What was found
In the untrained state, acute RE increased both myofibrillar (67%, P < 0.02) and mitochondrial protein synthesis (69%, P < 0.02). After 10 weeks of training, RE only increased myofibrillar protein synthesis (36%, P = 0.05). In contrast, EE increased mitochondrial protein synthesis in both untrained (154%, P < 0.05) and trained states (105%, P < 0.05), but did not increase myofibrillar protein synthesis in either state. Acute RE and EE both elevated Akt-mTOR-p70S6K phosphorylation with minor differences between modes, whereas 10 weeks of RE training increased basal Akt-mTOR-p70S6K phosphorylation but EE training did not.
Why it matters
This study demonstrates that chronic training refines muscle protein synthesis from a broad, non-specific response in untrained muscle to a phenotype-specific adaptation tailored to the exercise modality.
Limits
The abstract does not disclose the sample size or whether participants were randomized to training modes. The cohort was restricted to young healthy men, limiting generalizability to women, older individuals, or clinical populations. Upstream signaling phosphorylation failed to fully explain the fraction-specific divergence in protein synthesis.
Cited by
- supports Muscle protein synthesis increases after both endurance-type exercise and resistance-type exercise.