Untrained individuals develop muscle soreness and increased serum creatine kinase
(CK) activity in the blood after strenuous, unaccustomed exercise. An unpublished
observation in our laboratory revealed that trained weightlifters also experience
considerable soreness after unaccustomed exercise, but may not show a dramatic CK
response. This study examined the CK and soreness responses to strenuous exercise
in weight-lifters (TR, n = 10) and untrained subjects (UTR, n = 10). Trained subjects
had a minimum of three years weightlifing experience, and regularly performed squats
and leg presses. Untrained subjects had not participated in any regular resistance
exercise for the past three years. Following two acclimation sessions, subjects reported
to the lab on seven consecutive days and on the tenth day after knee extensor exercise.
Weight training sessions occurred on day 1 for the knee extensors (KE) and day 2 for
the knee flexors (KF). The weight training consisted of these exercises (sets): squat
(5), leg press (3), leg extension and lunge (3) for the KE, double leg curls (6),
single leg curls (3), stiff-legged deadlifts (4, TR group only) for the KF at 12 RM
for all exercises. To document the stress due to exiercise, the loss in strength (isometric
peak torque, IPT) was assessed on a Biodex isokinetic dynamometer. Maximal voluntary
IPT of the KE at 90 and the KF at 80 decreased 17-30 % with mo significant differences
between groups. Muscle soreness during simulated squat leg curl movement was assessed
by a 100 mm visual analog scale (VAS). Average peak KE soreness was 76 mm for TR and
58 mm for UTR, KF soreness was 60 mm for TR and 47 mm for UTR post-exercise. Serum
CK levels were significantly different between groups with a peak of 1349 IU for TR
and 3272 IU for the UTR (p<0.01). Although the TR group experienced greater soreness
than the UTR, peak serum CK activity was significantly lower, suggesting that trained
individuals can develop severe soreness without the same degree of increase in serum
CK activity observed in untrained individuals.
Key words
Creatine kinase - weight training - soreness - flexibility - strength
