Changes in Intra-Set Biomechanics During a 3RM Deadlift in Strength-Trained Women: A Biomechanical Analysis

The conventional deadlift is frequently performed in multiple-repetition sets at loads exceeding 80% of one-repetition maximum (RM) to increase maximal strength in the posterior chain. Fatigue-induced intra-set movement alterations have been observed in various exercises and loading ranges, but whether they occur under strength-specific deadlift conditions remains poorly understood. This study compared the intra-set development of spinal and lower extremity kinematics, net joint moments (NJMs) of the lower extremities, and surface electromyography (sEMG) amplitudes during a 3RM deadlift using statistical parametric mapping. Ten strength-trained women (body mass: 69.2 ± 8.1 kg, height: 166.3 ± 3.1 cm, age: 23.2 ± 3.7 years) lifted 100.6 ± 18.1 kg for a set of 3RM deadlifts. Across repetitions, spinal flexion and hip extension angles increased, while barbell velocity and peak angular hip extension velocity decreased. In contrast, hip NJMs and sEMG amplitudes showed minimal or no significant differences between repetitions. These findings suggest that as fatigue accumulates during a 3RM set, lifting capacity is maintained primarily through kinematic adjustments rather than increased hip extensor contribution.