Effects of different resistance training loads, exercises, and volume-regulated proximities to failure on acute and short-term neuromuscular, perceptual, and metabolic responses

This study investigated the effects of resistance training (RT) proximity-to-failure on acute and short-term neuromuscular, perceptual, and metabolic responses, across different loads and exercises. In a randomised crossover design, 18 participants completed six RT sessions, performing six sets of the free-weight barbell back squat and prone row using a moderate (i.e. 65% one repetition maximum (1RM)) or heavy (i.e. 85% 1RM) load and different proximities-to-failure (i.e. momentary muscular failure, 1-repetition in reserve (RIR), or 3-RIR) for each condition. Participants returned 24 h later, assessing neuromuscular function and perceived muscle soreness. Increases in neuromuscular fatigue, perceptual fatigue, and metabolic stress were seen as RT was performed closer to momentary muscular failure, with back squats and 65% 1RM eliciting more fatigue than prone rows and 85% 1RM, respectively. Furthermore, within-session kinematics decreased as proximity-to-failure neared, except when performing prone rows with 85% 1RM. Additionally, more total repetitions were completed when training closer to momentary muscular failure with 65% 1RM back squats and both loads in the prone row. These findings demonstrate that while neuromuscular fatigue, perceptual fatigue, and metabolic stress increases with a closer proximity-to-failure, practitioners must also consider the exercise and load being used to maintain performance and mitigate fatigue.