Acute Effects of Interset Proprioceptive Neuromuscular Facilitation Stretching on Repetition Performance and Blood Lactate Responses in Resistance-Trained Young Men

Purpose : This study aimed to investigate the acute effects of different interset proprioceptive neuromuscular facilitation (PNF) stretching protocols on repetition performance, total load, blood lactate concentration, and rating of perceived exertion during a resistance training session. Methods : Twelve resistance-trained men (age: 20.83 [1.03] y; height: 1.79 [0.04] m; body mass: 73.50 [5.60] kg; body mass index: 22.99 [1.67] kg/m 2 ) participated in a randomized crossover design. Participants completed 4 interset rest protocols: Combined PNF (COM), Hold–Relax (HR), Contract–Relax (CR), and Passive Rest (PASREST). Butterfly and lat pulldown exercises were performed, with all sets completed to muscular failure. Repetition performance, total load, blood lactate concentration, and rating of perceived exertion were assessed for each protocol. Results : The CR protocol resulted in higher repetition performance and total load compared with PASREST and HR across both exercises ( P  P  P   Conclusions : Among the interset PNF stretching protocols, the CR method provides the most balanced performance–fatigue profile, combining high repetition performance with lower perceived exertion. In contrast, the COM may offer a metabolically favorable response, as indicated by lower lactate concentrations at selected time points, although this is accompanied by higher perceptual load. These findings should be considered exploratory and hypothesis-generating, given the small sample size and the absence of prospective registration. Practical Applications : Interset PNF strategies may be used to optimize performance and metabolic responses in resistance-trained individuals, particularly in multiset, upper-body resistance training performed to muscular failure. Coaches may select specific protocols based on training goals, using CR to sustain performance with lower perceptual strain, or COM when targeting metabolic responses despite higher perceptual load.