The relationship between serum estrogen, testosterone, and calcium concentration and serum creatine kinase after high-load eccentric muscle contractions in high and low creatine kinase responder

The purpose of this study was to identify the relationship between serum estrogen and testosterone concentration and serum creatine kinase (CK) activity in low and high creatine kinase responders following high-force eccentric contractions. A secondary purpose was to identify the relationship between serum calcium concentration and serum CK activity following high-force eccentric contractions. Nineteen men (age = 24.7 +/- 4.3 yr) and twelve women (age = 22.6 +/- 4.0 yr) participated in the study. Measurements were conducted on blood obtained pre, immediately, 24, 48, 72, and 96 hours following high-force eccentric hamstring contractions. Subjects were divided into low and high (p < .001) peak CK responder groups by gender. There was no difference in sex hormone concentration between responder groups within genders (p > .05). A significant relationship was found between estrogen and CK in low responder males at 24 and 48 hours (p < .05). A significant relationship was found at 96 hours (p < .05) in low responder females. No relationship existed between testosterone and CK in low responder males or females (p > .05). No relationships existed between sex hormones and CK in high responder males or females ( p > .05). Serum CK activity exhibited a significant change over time (p < .001) after high-force eccentric contractions while serum calcium concentration did not (p > .05). Significant relationships were found between calcium and CK only in low responder males immediately and 72 hours after exercise (p < .05). Significant inverse relationships existed only in low responder females at 48 hours ( p < .05) and in high responder females at 24 hours (p < .01).;In conclusion, the results of this study suggest the following: (a) it is possible to identify high and low CK responder groups after high-force eccentric contractions but not at rest; (b) neither serum estrogen nor testosterone concentration can be used to explain the responder group difference in CK regardless of gender; and (c) CK activity does not reflect serum calcium concentration after high-force eccentric contractions. The variability of serum CK activity after eccentric exercise appears to be independent of serum sex hormone and calcium concentrations.