Concomitant changes in cross-sectional area and water content in skeletal muscle after resistance exercise.

ABSTRACT

This study investigated how one bout (1EX) and three bouts (3EX) of strenuous resistance exercise affected the cross-sectional area (CSA) and water content (WC) of the quadriceps muscle and patella tendon (PT), 4 h and 52 h after the last exercise bout. Ten healthy untrained male subjects performed 1EX with one leg and 3EX with the other leg. CSA and WC were measured with magnetic resonance imaging 10, 20 and 30 cm proximal to the tibia plateau (TP) for the muscle, and at the proximal, central and distal site for the PT prior to exercise, and 4 h and 52 h after the last exercise bout. Ten centimeter above the TP, muscle CSA was significantly increased at 4 h (1EX 13 ± 5%; 3EX 13 ± 4%) and 52 h (1EX 16 ± 5%; 3EX 16 ± 5%) compared with baseline. Muscle WC was significantly increased at 4 h (1EX 7 ± 1%; 3EX 6 ± 2%) and 52 h (1EX 8 ± 2%; 3EX 8 ± 3%) compared to baseline. PT central CSA was significantly reduced at 52 h (3EX 14 ± 2%) compared with baseline and (3EX 13 ± 1%) compared with 4 h. Present data demonstrate that strenuous resistance exercise results in an acute increase in muscle WC and underlines the importance of ensuring sufficient time between the last exercise bout and the determination of anatomical dimensions in muscles.