Creatine Kinase Elevation Following Eccentric Exercise in Females as a Marker for Training Stress

Abstract

Creatine kinase is an enzyme used by various tissue types to produce the energy substrate phosphocreatine (PCr). Cytosolic creatine kinase (CKc) is found within skeletal, cardiac as well as brain tissue and is responsible for catalyzing the phosphorylation of creatine to PCr when muscles are at rest. Observed CKc elevation following eccentric loading has previously been reported as an indicator for muscle adaptation or damage. PURPOSE: To determine the degree and duration of CKc elevation post-eccentric loading in females as a marker for training stress. METHODS: Baseline CKc levels were measured in four female subjects (22+2 yrs) prior to eccentric loading. Approximately 30 minutes of eccentric gymnastics strengthening activities were performed by all subjects. CKc was measured pre-exercise, 24 and 48 hours post-exercise (Reflotron®). RESULTS: Although a one-way Repeated Measures ANOVA was not significant (p>0.05), baseline CKc increased 23.96%, 130.97%, 442.53% and 133.66% at 24 hours. The insignificant difference is likely due to the high degree of CKc variability seen between subjects. All CKc values did follow the elevation trend expected at 24 hours post-exercise. CONCLUSION: Measures of CKc alone appear too variable to reply upon for a sole marker of training stress. When coupled with other parameters to account for variability between individuals, such as cortisol and/or a perceived effort or muscle soreness scale, CKc could provide a relevant measurement to help assess training stress.