Systems Physiology : Skeletal Muscle EFFECTS OF CIRCULATING ESTRADIOL ON EXERCISE-INDUCED CREATINE KINASE ACTIVITY

STEPHEN M. ROTH, RICHARD GAJDOSIK AND BRENT C. RUBY. Effects Of Circulating Estradiol On Exercise-Induced Creatine Kinase Activity. JEPonline. 2001;4(2):10-17. The present investigation sought to determine the effects of circulating estradiol (E2) and oral contraceptive use on serum creatine kinase (CK) activity following acute eccentric exercise. Ten college-aged female subjects were grouped according to their use (OBC, N=5) or non-use (NOBC, N=5) of an oral contraceptive. Both groups performed strenuous eccentric muscle actions (5 sets with 10 repetitions/set; ≥100% of concentric 1RM) during the menstrual cycle phase corresponding to low E2 concentrations. The OBC group had significantly lower E2 concentrations than the NOBC group (11.6 versus 27.2 pg/mL, respectively; p<0.01) prior to exercise. The results indicated that the OBC group (lower E2) had significantly higher CK activity at 48 and 72 hr post-exercise when compared to baseline CK activity (p<0.05). Although the NOBC (higher E2) group showed a slight increase in CK activity at 24, 48 and 72 hr post-exercise, values were not significantly different from pre-exercise. Perceived soreness values were generally dissociated from CK activity, but demonstrated a similar post-exercise response between groups. The results indicate that pre-exercise concentrations of circulating estradiol can affect serum CK activity following damaging eccentric exercise.