Resistance exercise increases leg muscle protein synthesis and mTOR signalling independent of sex

Abstract

Aim: Sex differences are evident in human skeletal muscle as the cross-sectional area of individual muscle fibres is greater in men than in women. We have recently shown that resistance exercise stimulates mammalian target of rapamycin (mTOR) signalling and muscle protein synthesis in humans during early post-exercise recovery. Therefore, the aim of this study was to determine if sex influences the muscle protein synthesis response during recovery from resistance exercise.

Methods: Seventeen subjects, nine male and eight female, were studied in the fasted state before, during and for 2 h following a bout of high-intensity leg resistance exercise. Mixed muscle protein fractional synthetic rate was measured using stable isotope techniques and mTOR signalling was assessed by immunoblotting from repeated vastus lateralis muscle biopsy samples.

Results: Post-exercise muscle protein synthesis increased by 52% in the men and by 47% in the women (P < 0.05) and was not different between groups (P > 0.05). Akt phosphorylation increased in both groups at 1 h post-exercise (P < 0.05) and returned to baseline during 2 h post-exercise with no differences between groups (P > 0.05). Phosphorylation of mTOR and its downstream effector S6K1 increased significantly and similarly between groups during post-exercise recovery (P < 0.05). eEF2 phosphorylation decreased at 1- and 2 h post-exercise (P < 0.05) to a similar extent in both groups.

Conclusion: The contraction-induced increase in early post-exercise mTOR signalling and muscle protein synthesis is independent of sex and appears to not play a role in the sexual dimorphism of leg skeletal muscle in young men and women.

Conflict of interest statement

Conflict of Interest

The authors have no conflict of interest.

Figures

Figure 1. Muscle protein synthesis (FSR)

Male (open bar) and female (closed bar) fractional synthesis rates (FSR) following an overnight fast (baseline) and the average FSR for the 2 hours following heavy resistance exercise (post-exercise recovery). Each subject performed 10 sets of 10 repetitions of bilateral knee extension in the seated position. Data are expressed as mean ± SE (N=9 men; N=8 women); *P

Figure 2. Representative images of immunoblots

Male and female representative leg muscle biopsy samples at Baseline, and at the 1st and 2nd hour of post-exercise recovery.

Figure 3. Akt

Phosphorylation status of Akt at Ser473 during the 1st and 2nd hour of post-exercise recovery. No difference was detected at baseline between men and women (data not shown). Data are expressed as percent change form baseline ± SE (N=9 men; N=8 women); *P<0.05 vs. Baseline, †P<0.05 vs. Male.

Figure 4. mTOR

Phosphorylation status of mTOR at Ser2448 during the 1st and 2nd hour of post-exercise recovery. No difference was detected at baseline between men and women (data not shown). Data are expressed as percent change form baseline ± SE (N=9 men; N=8 women); *P<0.05 vs. Baseline.

Figure 5. S6K1

Phosphorylation status of S6K1 at Thr389 during the 1st and 2nd hour of post-exercise recovery. No difference was detected at baseline between men and women (data not shown). Data are expressed as percent change form baseline ± SE (N=6 men; N=6 women); *P<0.05 vs. Baseline.

Figure 6. eEF2

Phosphorylation status of eEF2 at Thr56 during the 1st and 2nd hour of post-exercise recovery. No difference was detected at baseline between men and women (data not shown). Data are expressed as percent change form baseline ± SE (N=9 men; N=7 women); *P<0.05 vs. Baseline.