Resistance exercise enhances mTOR and MAPK signalling in human muscle over that seen at rest after bolus protein ingestion


S. M. Phillips, PhD, Exercise Metabolism Research Group, Department of Kinesiology, McMaster University, 1280 Main St. W., Hamilton, ON L8S 4K1, Canada.


Aim:  Feeding protein after resistance exercise enhances the magnitude and duration of myofibrillar protein synthesis (MPS) over that induced by feeding alone. We hypothesized that the underlying mechanism for this would be a greater and prolonged phosphorylation of signalling involved in protein translation.

Methods:  Seven healthy young males performed unilateral resistance exercise followed immediately by the ingestion of 25 g of whey protein to maximally stimulate MPS in a rested and exercised leg.

Results:  Phosphorylation of p70 ribosomal protein S6 kinase (p70S6K) was elevated (< 0.05) above fasted at 1 h at rest whereas it was elevated at 1, 3 and 5 h after exercise with protein ingestion and displayed a similar post-exercise time course to that shown by MPS. Extracellular regulated kinase1/2 (ERK1/2) and p90 ribosomal S6 kinase (p90RSK) phosphorylation were unaltered after protein ingestion at rest but were elevated (< 0.05) above fasted early in recovery (1 h) and were greater for the exercised-fed leg than feeding alone (main effect; < 0.01). Eukaryotic elongation factor 2 (eEF2) phosphorylation was also less (main effect; < 0.05) in the exercised-fed leg than in the rested leg suggesting greater activity after exercise. Eukaryotic initiation 4E binding protein-1 (4EBP-1) phosphorylation was increased (< 0.05) above fasted to the same extent in both conditions.

Conclusion:  Our data suggest that resistance exercise followed by protein feeding stimulates MPS over that induced by feeding alone in part by enhancing the phosphorylation of select proteins within the mammalian target of rapamycin (p70S6K, eEF2) and by activating proteins within the mitogen-activated protein kinase (ERK1/2, p90RSK) signalling.