Creatine kinase release and clearance using MM variants following repeated bouts of eccentric exercise. Med. Sci. Sports Exerc., Vol. 30, No. 7, pp. 1059-1065, 1998.
Purpose: This study investigated the release and clearance of plasma CK-MM (muscle) isoforms following two bouts of eccentric exercise to determine whether enhanced enzyme clearance could in part explain the blunted creatine kinase (CK) response to a second bout of exercise.
Methods: Nonweight trained college-aged male subjects performed both bouts of 50 forced lengthening contractions of the forearm flexor muscles separated by 6 d either with the same arm (CON; N = 4) or with one arm followed by the contralateral arm (EXP; N = 4). Range of motion, arm circumference, maximal isometric strength, perceived muscle soreness, total CK (TCK), and MM variants were assessed. Each MM isoform was measured as a percentage of TCK activity and in absolute activity (IU·L−1) following isoelectric separation and densitometry. The MM1:MM3 ratio, calculated from absolute concentrations, was used to indicate periods of release and clearance.
Results: Non-CK criterion measures indicated that similar damage occurred in both arms for EXP (P > 0.05), whereas CON exhibited a blunted response on bout 2 (P < 0.01). Postbout 1, TCK peaked at 96 h for CON (3530 ± 927 IU·L−1) and EXP (6683 ± 433 IU·L−1) (P < 0.01). Postbout 2, CON TCK showed no additional increase; however, a second rise in EXP TCK reached its highest point by day 5 (3602 ± 1190 IU·L−1). Expectedly, %MM1 and the MM1:MM3 ratio were increased after bout 1 in both groups (P < 0.01). New CK release was observed postbout 2 in both groups as indicated by an increase in %MM1 (P < 0.01), despite no increase in TCK after bout 2 for CON and a smaller CK response for EXP.
Conclusion: Accelerated clearance of CK seems to be one factor contributing to the blunted response of this enzyme following a repeated bout of exercise.
Department of Exercise Science, University of Massachusetts, Amherst, MA 01003
Submitted for publication September 1997.
Accepted for publication January 1998.
The authors thank Dr. Stella Volpe and Ned Debold for their helpful comments on this manuscript.
Address for correspondence: Dr. Priscilla Clarkson, Totman Bldg., Department of Exercise Science, University of Massachusetts, Amherst, MA 01003. E-mail: email@example.com.