SEX COMPARISON OF KNEE EXTENSOR SIZE, STRENGTH, AND FATIGUE ADAPTATION TO SPRINT INTERVAL TRAINING

Regular sprint interval training (SIT) improves whole-body aerobic capacity and muscle oxidative potential, but very little is known about knee extensor anabolic or fatigue resistance adaptations, or whether effects are similar for men and women. The purpose of this study was to compare sex-related differences in knee extensor size, torque-velocity relationship, and fatigability adaptations to 12-week SIT. Sixteen men and 15 women (mean [SEM] age: 41 [+/- 2.5] years) completed measurements of total body composition assessed by dual energy X-ray absorptiometry, quadriceps muscle cross-sectional area (CSA(Q)) assessed by magnetic resonance imaging, the knee extensor torque-velocity relationship (covering 0-240 degrees.s(-1)) and fatigue resistance, which was measured as the decline in torque from the first to the last of 60 repeated concentric knee extensions performed at 180 degrees.s(-1). Sprint interval training consisted of 4 x 20-second sprints on a cycle ergometer set at an initial power output of 175% of power at V?o(2)max, 3 times per week for 12 weeks. Quadriceps muscle cross-sectional area increased by 5% (p = 0.023) and fatigue resistance improved 4.8% (p = 0.048), with no sex differences in these adaptations (sex comparisons: p = 0.140 and p = 0.282, respectively). Knee extensor isometric and concentric torque was unaffected by SIT in both men and women (p > 0.05 for all velocities). Twelve-week SIT, totaling 4 minutes of very intense cycling per week, significantly increased fatigue resistance and CSA(Q) similarly in men and women, but did not significantly increase torque in men or women. These results suggest that SIT is a time-effective training modality for men and women to increase leg muscle size and fatigue resistance.

Automated summary

This study compared sex-related differences in knee extensor size, torque-velocity relationship, and fatigue resistance adaptations to 12-week SIT. The results showed that SIT significantly increased fatigue resistance and quadriceps muscle cross-sectional area similarly in men and women, but did not significantly affect torque in either gender.