Purpose: To determine if the mathematical model used to derive critical power could be used to identify the critical resistance (CR) for the deadlift; compare predicted and actual repetitions to failure at 50%, 60%, 70%, and 80% 1-repetition maximum (1RM); and compare the CR with the estimated sustainable resistance for 30 repetitions (ESR30). Methods: Twelve subjects completed 1RM testing for the deadlift followed by 4 visits to determine the number of repetitions to failure at 50%, 60%, 70%, and 80% 1RM. The CR was calculated as the slope of the line of the total work completed (repetitions × weight [in kilograms] × distance [in meters]) vs the total distance (in meters) the barbell traveled. The actual and predicted repetitions to failure were determined from the CR model and compared using paired-samples t tests and simple linear regression. The ESR30 was determined from the power-curve analysis and compared with the CR using paired-samples t tests and simple linear regression. Results: The weight and repetitions completed at CR were 56 (11) kg and 49 (14) repetitions. The actual repetitions to failure were less than predicted at 50% 1RM (P < .001) and 80% 1RM (P < .001) and greater at 60% 1RM (P = .004), but there was no difference at 70% 1RM (P = .084). The ESR30 (75 [14] kg) was greater (P < .001) than the CR. Conclusions: The total work-vs-distance relationship can be used to identify the CR for the deadlift, which reflected a sustainable resistance that may be useful in the design of resistance-based exercise programs.

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.