Changes in Fatigue Are the Same for Trained Men and Women after Resistance Exercise

Purpose To measure changes in fatigue and knee-extensor torque in the 48 h after trained men and women completed a full-body resistance exercise session. Methods Eight trained women (mean +/- SD: age, 25.6 +/- 5.9 yr; height, 1.68 +/- 0.06 m; mass, 71.0 +/- 8.6 kg) and eight trained men (age, 25.5 +/- 6.2 yr; height, 1.79 +/- 0.05 m; mass, 86.4 +/- 9.8 kg) performed a full-body resistance exercise session based on real-world athletic practice. Measurements were performed before and after the exercise session, as well as 1, 24, and 48 h after the session. Fatigue and pain were measured with standardized self-report measures. Maximal isometric contractions with the knee extensors and superimposed femoral nerve stimulation were performed to examine maximal torque, rate of torque development, voluntary activation, and muscle contractility. Two sets of 10 isokinetic contractions (60 degrees center dot s(-1)) with the knee extensors were performed during the protocol with use of near-infrared spectroscopy to assess muscle oxygenation. EMG were recorded from two quadriceps muscles during all isometric and isokinetic contractions. Results Fatigue was increased from baseline for both sexes until 48 h after training (P < 0.001). Maximal torque and evoked twitch amplitudes were similarly reduced after exercise for men and women (P < 0.001). Voluntary activation and EMG amplitudes were unchanged after the training session. Muscle oxygenation was 13.3% +/- 17.4% (P = 0.005) greater for women during the isokinetic repetitions, and the values were unchanged after the training session. Conclusions This is the first study to show similar changes in the fatigue reported by trained men and women in the 48 h after a training session involving full-body resistance exercises. Sex differences in muscle oxygenation during exercise do not influence the reductions in muscle force, activation, or contractility after the training session.