Sprint exercise enhances skeletal muscle p70S6k phosphorylation and more so in women than in men
Correspondence: M. Esbjörnsson, Division of Clinical Physiology, Karolinska University Hospital, Huddinge, SE-141 86 Stockholm, Sweden. E-mail: email@example.com
Sprint exercise is characterized by repeated sessions of brief intermittent exercise at a high relative workload. However, little is known about the effect on mTOR pathway, an important link in the regulation of muscle protein synthesis. An earlier training study showed a greater increase in muscle fibre cross-sectional area in women than men. Therefore, we tested the hypothesis that the activation of mTOR signalling is more pronounced in women than in men. Healthy men (n = 9) and women (n = 8) performed three bouts of 30-s sprint exercise with 20-min rest in between.
Multiple blood samples were collected over time, and muscle biopsy specimens were obtained at rest and 140 min after the last sprint.
Serum insulin increased by sprint exercise and more so in women than in men [gender (g) × time (t)]: P = 0.04. In skeletal muscle, phosphorylation of Akt increased by 50% (t, P = 0.001) and mTOR by 120% (t, P = 0.002) independent of gender. The elevation in p70S6k phosphorylation was larger in women (g × t, P = 0.03) and averaged 230% (P = 0.006) as compared to 60% in men (P = 0.04). Phosphorylation rpS6 increased by 660% over time independent of gender (t, P = 0.003). Increase in the phosphorylation of p70S6k was directly related to increase in serum insulin (r = 0.68, P = 0.004).
It is concluded that repeated 30-s all-out bouts of sprint exercise separated by 20 min of rest increases Akt/mTOR signalling in skeletal muscle. Secondly, signalling downstream of mTOR was stronger in women than in men after sprint exercise indicated by the increased phosphorylation of p70S6k.