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

Abstract

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. Pearson's 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