Contributions of Maximal Strength and Body Composition Characteristics to Resistance Exercise Performance at the Critical Load

Dinyer TK, Byrd MT, Succi PJ, Clasey JL, Bergstrom HC. Contributions of Maximal Strength and Body Composition Characteristics to Resistance Exercise Performance at the Critical Load. JEPonline 2020;23(3):25-37. The purpose of this study was to examine the contributions of maximal strength (1-repetition maximum, 1RM), total body mineral-free lean mass (MFLM_Total) and thigh mineral-free lean mass (MFLM_Thigh) on the number of repetitions to failure for the deadlift performed at critical load (CL) to elucidate the characteristics that define the CL threshold. Eighteen individuals completed a DXA scan to assess MFLM_Totaland MFLM_Thigh, 1RM testing, and repetitions to failure at 50%, 60%, 70%, and 80%1RM to determine CL, and repetitions to failure at CL. Zero-order correlations, full and stepwise multiple regression analyses were used to determine the relationships, relative contributions of, and most parsimonious predictor among 1RM, MFLM_Total, and MFLM_Thighand performance at CL. The subjects completed 52 ± 15 reps at CL (55 ± 13 kg). The MFLM_Totalhad the highest correlation with the performance at CL (r = -0.534), followed by 1RM (r = -0.490) and MFLM_Thigh(r = -0.438). The 1RM (1.7%), MFLM_Total(29.5%), and MFLM_Thigh(11.9%) accounted for 43.1% of the explained variance in the performance at CL. Only MFLM_Totalcontributed significantly to the prediction of repetitions completed at CL. The 1RM, MFLM_Total, and MFLM_Thighaccounted for less than 50% of the explained variance in the performance at CL, suggesting other factors such as blood flow and muscle oxygenation may better explain the variance in performance at CL.