Changes in Heart Rate, Blood Lactate Concentration, Muscle Fatigue, and Smash Accuracy Following Repeated Smash Performance in Elite Badminton Players

OBJECTIVES This study aimed to investigate the changes in heart rate, blood lactate concentration, neuromuscular fatigue, and smash accuracy during repeated high-intensity smash performance in elite badminton players.METHODS Fifteen elite badminton players participated in a repeated smash protocol consisting of three sets (20 smashes per set) with a 30-second rest interval between sets. Heart rate (HR) and blood lactate concentration (BLa) were measured to assess physiological responses. Muscle fatigue was assessed using surface electromyography by analyzing the median frequency (MDF) of the vastus lateralis (VL) and biceps femoris (BF). Smash accuracy was evaluated by quantifying the number of errors, defined as net faults or out-of-bounds shots, through video analysis. Data were analyzed using one-way repeated-measures ANOVA with Bonferroni post-hoc tests.RESULTS HR increased significantly as the sets progressed (<i>p</i> < 0.05), with values in sets 2 and 3 being significantly higher than in set 1. Additionally, BLa increased significantly across time points (<i>p</i> < 0.05), with the highest values observed at Rec-3min. The number of smash errors also increased significantly over time (<i>p</i> < 0.05), with a marked increase in the final set compared to the first. However, no significant changes were observed in MDF values of the VL and BF (<i>p</i> > 0.05).CONCLUSIONS The decline in smash accuracy is associated with accumulated physiological load, reflected by increased cardiovascular and metabolic responses, rather than changes in EMG-based lower-limb muscle fatigue.