Muscle damage and resting metabolic rate after acute resistance exercise with an eccentric overload.

PURPOSE: The purpose of this investigation was to determine whether muscle damage caused from acute resistance exercise with an eccentric overload would influence resting metabolic rate (RMR) up to 72 h postexercise in resistance-trained (RT) and untrained (UT) subjects.
METHODS: Nine RT and 9 UT male subjects (mean +/- SD; age = 20.7 +/- 2.1 yr; body mass = 79.0 +/- 1.4 kg; height = 178.4 +/- 3.1 cm; and body fat = 10.2 +/- 1.6%) were measured for RMR, creatine kinase concentration ([CK]), and rating of perceived muscle soreness (RPMS) on five consecutive mornings. To induce muscle damage, after the measurements on day 2, each subject performed leg presses that emphasized the eccentric movement for 8 sets at his six-repetition maximum (6-RM).
RESULTS: Compared with baseline, the RMR (kJ x d(-1) and kJ x kg FFM(-1) x h(-1) was significantly elevated for RT and UT at 24 h and 48 h postexercise. From 24 h to 48 h to 72 h postexercise, RMR significantly decreased within both groups. The UT group had a significantly higher RMR at 24 h (9,705.4 +/- 204.5 kJ x d(-1)) and 48 h postexercise (8,930.9 +/- 104.4 kJ x d(-1)) when compared with the RT group (9,209.3 +/- 535.3 and 8,601.7 + 353.7 kJ x d(-1)). Both [CK] and RPMS showed a similar time course.
CONCLUSION: There was a significantly higher [CK] for the UT group at 24 h postexercise (320.4 +/- 20.1 U x L(-1)) and for both [CK] and RPMS at 48 h (1,140.3 +/- 37.1 U x L(-1) and 4.4 +/- 0.5, respectively) and 72 h postexercise (675.9 +/- 41.7 U x L(-1) and 1.67 +/- 0.5, respectively) when compared with the RT group (24 h, 201.9 +/- 13.4 U x L(-1); 48 h, 845.4 +/- 30.7 U x L(-1) and 3.7 +/- 0.5: and 72 h postexercise, 420.2 +/- 70.2 U x L(-1) and 0.89 +/- 0.3). These data indicate that eccentrically induced muscle damage causes perturbations in RMR up to 48 h postexercise.