Abstract
The purpose of this study was to determine whether there was a difference in the amount of soreness and creatine kinase (CK) produced between isokinetic eccentric knee flexion and extension exercise. The subjects included 24 female college students with a mean age of 21.6 ± 2.0 yr. Two groups of eight subjects performed three sets of 35 isokinetic unidirectional eccentric contractions at 120 deg/sec on a Biodex isokinetic dynamometer. Group 1 performed eccentric contractions of the knee extensors (quadriceps femoris muscle) and group 2, knee flexors (hamstring muscle). Group 3 served as a control. Subjects in the exercise groups attempted to maintain the intensity of the contractions at 80% of their respective isokinetic concentric 120 deg/sec peak torque, and each set was separated by a 2-min rest period. Blood samples were collected for CK, an indicator of muscle damage, at the following intervals: pre-exercise, and 1, 24, 48, and 72 h postexercise. Perceived soreness of the quadriceps femoris muscle and hamstring muscles was assessed by a 0–10 point scale, concurrently. The highest postexercise CK and soreness values were 261, 6,037, and 87 IU/L and 0.9, 4.1, and 0 pain scale units for groups 1, 2, and 3, respectively. Analyses of variance using a split plot factorial design found significant log CK (F = 25.0, P < 0.01) and soreness (F = 41.7, p < 0.01) differences between the three groups. Contrast-contrast testing found significantly higher elevations of log CK and soreness 48 and 72 h postexercise in group 2 when compared with group 1 (p < 0.01) and group 3(p < 0.01). This study demonstrates that after isokinetic eccentric exercise of this type the hamstring muscle is markedly more vulnerable to delayed muscle soreness and muscle damage than the quadriceps femoris muscle.