Variability in Serum Creatine Kinase Response After Eccentric Exercise of the Elbow Flexors

There is a large inter-subject variability in serum creatine kinase (CK) response after eccentric exercise. This study examined and compared the variability of CK activity, other serum protein increases (aspartate aminotransferase, alanine amino-transferase, lactate dehydrogenase, aldolase, myoglobin), changes in muscle damage indicators (maximal isometric force: MIF, relaxed and flexed elbow joint angle: RANG and FANG, circumference: CIR, and muscle soreness level: SOR), and changes in magnetic resonance (MR) images. Ten male subjects (21.7 ±1.6yrs) performed 24 maximal eccentric actions of the elbow flexors, and measurements except MR images were taken immediately before and after, and for 10 days after exercise. MR images were taken 7 days after exercise. A large variability in peak CK response (236 - 25,244 IU · l^-1) was found among subjects. Spearman rank-order correlation coefficients (r) revealed significant correlations of peak CK with peak serum protein levels (r = 0.79-0.95), peak changes in MIF (r = 0.73-0.79), RANG (r = 0.69), and CIR (r = 0.91). The higher the peak CK levels, the more profound the abnormality in the MR images and the larger the changes in MR signal intensity (r = 0.90 - 0.94). It is concluded that the large variability in CK response after exercise seems to be related to the variability in exercise-induced muscle damage.

Key words

Muscle damage - eccentric exercise - creatine kinase - aspartate aminotransferase - aldolase - myoglobin - MRI