The effect of eccentric hamstring exercise on serum creatine kinase and serum creatine kinase-MB in females of varying menarchial statu

The purpose of this study was to investigate the effects of eccentric hamstring exercise on serum creatine kinase (CK) and CK isoenzyme MB activities in females of varying menarchial status. A secondary purpose was to determine the relationship among serum CK, serum CK-MB activities, and serum estradiol concentrations following eccentric hamstring exercise in females of varying menarchial status.;Forty females volunteered for the study. Fifteen females were sexually mature, fifteen females were sexually immature, and ten females were post menopausal. Baseline serum CK activity, serum CK-MB activity, and serum estradiol concentrations were assayed in blood samples drawn prior to exercise. Serum CK and CK-MB activities were determined in blood samples 24, 48, and 72 hours post exercise. The treatment for the three groups consisted of an eccentric hamstring exercise on a leg curl machine. Each subject performed six sets of ten repetitions at 110 percent of their concentric 1RM.;Results revealed significantly higher serum estradiol concentrations in menarchial females (p $<$.0001). No differences existed between post menopausal and pre menarchial females. A two way repeated measures ANOVA revealed a significant efflux of CK (p $<$.001) and CK-MB (p $<$.007) following exercise. Serum CK and CK-MB activities of menarchial females were significantly greater than pre menarchial and post menopausal females following exercise (p $<$.002). Pearson product-moment correlation coefficients revealed a significant (p $<$.0001) relationship between serum CK and serum CK-MB activities 24, 48, and 72 hours following exercise. This suggested that the response in serum CK were paralleled by the response in CK-MB post exercise. Pearson product-moment correlation coefficients revealed a significant (p $<$.003) inverse relationship among serum estradiol concentrations and baseline serum CK and serum CK-MB activities. No relationship existed among post exercise efflux of CK and CK-MB and concentrations of serum estradiol. Correlation coefficients revealed a significant relationship between the 1RM and post exercise efflux of CK and CK-MB (p $<$.05). It was concluded that high concentrations of serum estradiol reduced the efflux of CK and CK-MB from muscle at rest, however, serum estradiol concentration did not influence the efflux of CK and CK-MB from muscle after a bout of eccentric hamstring exercise. The variations in response of the efflux of CK and CK-MB in the three groups was probably due to differences in intensity.