Serum Creatine Kinase Response To Initiation Of Resistance Training Predicts Hypertrophic Response In Men
Richard L. Seip, FACSM1, Heather Gordish-Dressman2, Joseph M. Devaney2, Paul Gordon, FACSM3, Priscilla Clarkson, FACSM4, Theodore J.
PURPOSE: Myofibrillar damage that is incurred as a result of resistance exercise is hypothesized to be a precursor to skeletal muscle hypertrophy. Serum creatine kinase
activity (CK) responds to acute exercise in proportion to the extent and severity of muscle injury. In a subset of subjects from the FAMuSS study, we tested the hypothesis that
the increase in CK measured upon the initiation of training is correlated with the upper arm muscle hypertrophic response observed after 12 weeks.
METHODS: 51 men and 51 women ages 18-39 who were previously untrained underwent 12 weeks of resistance training exercise in the nondominant arm. Serum CK was
measured at baseline prior to bout 1; 48 h following bout 1 and before bout 2; and 96 h following bout 1, which was also 48 h after bout 2. Upper arm muscle size was
measured using magnetic resonance imaging (MRI) at baseline and week 12.
RESULTS: Women and men significantly increased upper arm muscle cross sectional area and total volume. Men demonstrated a wider range of peak CK response (11 to
6040 units) compared to women (26 to 915). CK increases were log transformed for correlational analyses. Data are mean ± sd.
CONCLUSIONS: The CK response to the initiation of training predicted the muscle hypertrophy response at 12 weeks in men. The data support the hypothesis that muscle
injury is a precursor to the increase in muscle size in men but not women, at least in previously untrained subjects undertaking 2x per week resistance training according to
standard guidelines.
