The effect of 2 consecutive days of intense resistance exercise on sleep in untrained adults

The purpose of this study was to investigate the effect of daytime intense resistance exercise for 2 consecutive days on sleep including changes in central nervous system function, autonomic function, and core body temperature on the following nights. Nine healthy male participants (23.4 ± 1.8 years of age) performed strenuous resistance exercise twice per day for 2 consecutive days. Resistance exercise in the morning included four lower body exercises. Squats and knee extensions consisted of five sets of 10 repetitions at a 10-repetition maximum (RM; approximately 75% of 1 RM), with a 1-min rest period between each set. Calf raises consisted of five sets of 30 repetitions at 10 RM. Resistance exercise in the afternoon included seven upper body exercises, each with four sets of 10 repetitions at a 10 RM. Polysomnographic, heart rate, and core body temperature measurements were performed during sleep for three days (baseline, Ex-1, and Ex-2). Of the polysomnographic parameters, there was a significant reduction in stage 2 sleep at Ex-2 (225.56 ± 18.78 min) compared to other nights. For heart rate variability, the high-frequency component at Ex-2 was significantly lower in the first cycle than in the third cycle in non-rapid eye movement sleep and rapid eye movement sleep. Intense resistance exercise for 2 consecutive days causes the inhibition of parasympathetic nervous system activity during sleep.