The Sensitivity of the Critical Resistance Model to Detect Sex-Related Differences in Fatigue During Submaximal Muscular Contractions

Purpose: Critical resistance (CR) is a fatigue threshold that, theoretically, estimates the highest sustainable resistance for repeated skeletal muscle contractions. Men are typically more susceptible to fatigue than women during sustained muscular contractions. Therefore, the purpose of this study was to compare the CR between men and women to determine the sensitivity of the CR model to detect sex-related differences in fatigue at submaximal intensities. Methods: Ten men and 10 women completed one-repetition maximum (1RM) testing for the deadlift and repetitions to failure at 50%, 60%, 70%, and 80% of 1RM for the determination of CR. Repetitions to failure were then performed at the estimated CR. Results: The men had a greater absolute 1RM (168 ± 27 kg vs. 115 ± 11 kg) and CR (62 ± 14 kg vs. 48 ± 6 kg), but a lower relative CR (percent of 1RM; 37 ± 6% vs. 41 ± 2%) and completed fewer repetitions at CR (45 ± 14 repetitions vs. 58 ± 12 repetitions) compared to the women. Conclusions: The CR model was sensitive to detect sex-related differences in fatiguing muscular contractions of the deadlift. In addition, the men were more susceptible to fatigue than the women during performance of submaximal muscular contractions at CR, which may be related to sex-dependent physiological responses during fatiguing muscular contractions.