Temporal increase in muscle cross-sectional area as an acute effect of resistance exercise in resistance-trained and untrained individuals

摘要

The purpose of this study was to compare the temporal increase in muscle cross-sectional area (CSA) as the acute response of resistance exercise (RE) between resistance-trained and untrained groups, and investigate the factors that affect the muscle CSA.Resistance-trained ( n = 14) and untrained ( n = 14) subjects performed four kinds of triceps brachii RE.Muscle CSA and intracellular hydration (IH), were measured prior to and 5-, 30-, and 60-minute after RE.Pearsons correlation coefficient was calculated to clarify the relationships among percent increases in muscle CSA and IH, area under the Oyx-Hb curve, blood lactate concentration, and % maximum voluntary contraction (MVC)-root-mean-square (RMS) of electromyogram (EMG).At 5-minute after RE, muscle CSA increased significantly to 120.2 ± 6.3% in the resistance-trained group and 105.5 ± 2.3% in the untrained group ( p 0.01).However, neither group showed a significant difference between the values before and 30-minute after RE.In the resistance-trained group, there was a significant increase in IH at 5-minute post-RH ( p 0.01), and correlations were found between percent increases in muscle CSA and IH ( r = 0.70, p 0.01), area under the Oxy-Hb curve ( r = 0.77, p 0.01), and % MVC-RMS of EMG ( r = 0.72, p 0.01).The findings of this study suggest that measurements of muscle CSA in studies of muscle hypertrophy should be performed 30-minute or more after the last resistance exercise session, and muscle pump exercises should be conducted just before participation in bodybuilding, and physique contests.