Differential expression of muscle damage in humans following acute fast and slow velocity eccentric exercise

We sought to determine if the velocity of an acute bout of eccentric contractions influenced the duration and severity of several common indirect markers of muscle damage. Subjects performed 36 maximal fast (FST, n=8: 3.14 rad·s^-1) or slow (SLW, n=7: 0.52 rad·s^-1) velocity isokinetic eccentric contractions with the elbow flexors of the non-dominant arm. Muscle soreness, limb girth, plasma creatine kinase (CK) activity, isometric torque and concentric and eccentric torque at 0.52 and 3.14 rad·s^-1 were assessed prior to and for several days following the eccentric bout. Peak plasma CK activity was similar in SLW (4030±1029 U·l^-1) and FST (5864±2664 U·l^-1) groups, (p>0.05). Both groups experienced similar decrement in all strength variables during the 48 hr following the eccentric bout. However, recovery occurred more rapidly in the FST group during eccentric (0.52 and 3.14 rad·s^-1) and concentric (3.14 rad·s^-1) post-testing. The severity of muscle soreness was similar in both groups. However, the FST group experienced peak muscle soreness 48 hr later than the SLW group (24 hr vs. 72 hr). The SLW group experienced a greater increase in upper arm girth than the FST group 20 min, 24 hr and 96 hr following the eccentric exercise bout. The contraction velocity of an acute bout of eccentric exercise differentially influences the magnitude and time course of several indirect markers of muscle damage.