Serum Creatine Kinase Activity Varies with Ovulatory Status in Regularly Exercising, Premenopausal Women

Abstract

Background/Aims: The clinical complications associated with an unopposed estrogen environment and luteal phase defects observed in exercising women prompted the examination of the relationship of exercise and endogenous ovarian steroids with serum creatine kinase (CK) activity. Methods: Subjects (n = 34) were classified into three groups according to their exercise and menstrual status, sedentary and exercising ovulatory groups (SedOvul, ExOvul), and an exercising amenorrheic group (ExAmen). Daily urine samples were collected to assess urinary ovarian steroid exposure and menstrual status. Serum CK activity was assayed in each menstrual cycle of all subjects. Results: Exercise increased serum CK activity in all exercising subjects (p < 0.01), but the increase was greater in amenorrheic women compared to ovulatory women (SedOvul: 33.0 ± 3.4; ExOvul: 43.7 ± 4.1; ExAmen: 54.4 ± 3.6, p < 0.05). When the ovulatory women were further divided into those with normal steroid production (ExOvul subgroup) and those with a suppressed progesterone luteal phase environment (ExLPD), both the ExOvul (51.9 ± 5.4 IU/l) subgroup and ExAmen group had higher serum CK activity (p < 0.05) than the ExLPD (36.6 ± 5.2 IU/l) subjects or the sedentary controls. Conclusions: These data demonstrate the complex association between ovarian hormone status and the normal serum CK response to regular mechanical stress imposed by chronic exercise training.

The Effect of Gender and Menstrual Phase on Serum Creatine Kinase Activity and Muscle Soreness Following Downhill Running

“…Similarly, a previous study that included OC women in their active pill phase and naturally cycling eumenorrhoeic women in their mid-follicular phase reported a negative correlation between the CK response to downhill running and pre-exercise oestrogen concentration [20]. The coincident increase in progesterone with oestrogen in the ML phase may modulate the protective effect of oestrogen [19] and may explain why no noticeable difference was observed in the current study between the CK response in the EF and ML phases despite a significantly higher oestrogen concentration in the ML phase.…”

“…Resting serum CK activity has previously been reported to be higher in amenorrhoeic women athletes who have persistently low serum oestrogen concentrations compared with women athletes who have ovulatory menstrual cycles [19]. Women taking oral contraceptives (OC) tested during their active pill phase and therefore exposed to high exogenous synthetic oestrogen had a lower CK response 72 h after downhill running compared with eumenorrhoeic women not on oral contraceptives when tested in their mid-follicular phase with moderate to low endogenous oestrogen concentrations [20].…”

“…For example, in the condition of luteal phase-deficiency in women, which is characterised by a shortened luteal phase with suppressed progesterone secretions but normal oestrogen concentrations, resting CK activity is lower than in women who have a normal luteal phase characterised by concurrently elevated oestrogen and progesterone [19]. Furthermore, in a study in women (part taking OC and part naturally cycling), the luteal phase characterised by concurrently elevated oestrogen and progesterone, produced greater strength decrement and higher CK activity at 96 h after intensive eccentric resistance exercise than in the follicular phase with modest to low oestrogen and low progesterone [22].…”

Creatine-Kinase- and Exercise-Related Muscle Damage Implications for Muscle Performance and Recovery

“…Raised levels of serum CK were also found in regularly exercising pre-menopausal women compared to similar sedentary individuals [15]; this suggests that CK flux into the serum is a natural and normal reaction to regular exercise.…”

“…The mechanism(s) by which CK is cleared from the blood has not been fully elucidated, and it is likely that observed serum CK levels reflect complex interactions associated with energy status and scale of muscle disturbance. Thus, measured serum CK will reflect relative amounts of CK released, degree of enzyme activity of released CK, and the rate of clearance of CK from the serum [15]. …”