Abstract
Changes in muscle strength with aging appear before old age and are reported to precede a decrease in muscle mass. However, few studies have examined muscle function and Neuromuscular junctions (NMJ) differences in middle-aged and young populations. The purpose of this study was to compare the differences in physical activity, body composition, isokinetic muscle strength and NMJ according to the life cycle of the population aged 20–59 and to examine the correlation according to age. Physical activity (IPAQ), body composition (BIA), knee extension strength (PT, BW/PT, RTD180, AT), Neuromuscular junctions (CAF, NfL) were examined in young (age = 29.38 ± 3.38 years), middle-aged (50.54 ± 4.772 years) men. Middle-aged men showed lower physical activity (1.54 ± 0.66 and 2.15 ± 0.55), PT (170.55 ± 35.41Nm and 224.72 ± 41.02Nm), BW/PT (234.93 ± 50.05% and 295.48 ± 31.44), and RTD180 (94.86 ± 29.72Nm and 153.60 ± 33.02Nm) values and significantly higher NfL(11.29 ± 5.50pg/mL and 6.44pg/mL) than younger men. All of the above variables were significantly correlated with age. Simple regression analysis between strength and NMJ showed that PT, BW/PT, and RTD180 were negatively correlated with NfL. Our results suggest that changes in physical activity quality, isokinetic strength, and neuromuscular junction are clear from young to middle-aged men, suggesting that intervention techniques should be proposed to maintain muscle function before aging is evident.