Effect of Muscle Fatigue on the Torque Velocity Profile in Resistance Trained Males and Females

Introduction

Various studies have reported higher muscle fatigability in males compared to females. Few studies measure sex differences in fatigue through dynamic tasks. The aim of the present study was to compare fatigue in males versus females using both isometric and dynamic tasks.

Methods

Nineteen physically active young adults participated in this study (8 females and 11 males). Participants performed the torque-velocity profile (TVP) test on their first lab visit. On visits 2 and 3, they performed a short torque-velocity test before and immediately after two different fatiguing tasks: the critical load test on day 2, and a resistance exercise task (5 x 10) on day 3.

Results

Across all tests, absolute peak torque and power output were higher in males. When normalized to fat free mass (FFM) and leg FFM these differences were attenuated. Males were found to fatigue more rapidly during the critical load test than females, but calculated fatigue index was similar in both sexes. Similarly, absolute critical power (CP) and W-prime (W´) were higher in males, but PPO relative to CP and W´ relative to FFM were not different between sexes. The 5 x 10 task only led to a significant reduction in absolute and relative torque during the MVIC and at the slowest angular velocities in males, whereas females did not fatigue at any angular velocity.

Conclusion

The sex differences in fatigue were more pronounced at slower angular velocities and was not different between sexes at higher angular velocities, while normalization to FFM reduced sex differences in fatigability. Previously reported sex differences in fatigue are likely due to differences in absolute strength and PO which heightens the rate of fatigue in males following fatiguing resistance exercise task, while most but not all sex differences would diminish when normalizing to FFM.