Acute effects of low-load resistance exercise with different rest periods on muscle swelling in healthy young men

Abstract

The effects of high-load resistance training on muscle strength and muscle mass depend on rest periods between sets. However, whether differences in rest period length during low-load resistance exercise (RE) has an influence on improving muscle characteristics remains unclear. Better understanding such effects would enable us to prescribe low-load resistance exercise more safely and effectivity. The purpose of this study was to investigate the acute effects of low-load RE on muscle swelling with different length rest periods between sets. A total of 42 young men (age, 22.9 ± 2.4 years; height, 172.1 ± 5.4 cm; body mass, 65.6 ± 6.5 kg) were recruited to participate in this study. They were assigned to one of three groups with different rest periods between sets (20 s [seconds], 60 s, or 180 s). A total of 12 sets of 10 repetitions of RE with 30% of one repetition maximum on knee extensor muscles were performed. Muscle thickness of the vastus lateralis was measured using ultrasonography as an indicator of muscle swelling every 3 sets. Muscle thickness significantly increased after 3 sets of RE in the 20-s (3.9 ± 3.3%) and 60-s groups (5.9 ± 3.8%), but only after 12 sets in the 180-s group (4.3 ± 3.1%). RE with rest periods shorter than 60 s could result in exercise-induced muscle swelling after fewer sets of RE.