Short-term immobilization after eccentric exercise. Part II: creatine kinase and myoglobin.
OBJECTIVE
Although creatine kinase (CK) is commonly used as a marker of muscle damage, there is large variability in the response to exercise. We previously found short-term immobilization blunted the rise in plasma CK after eccentric exercise, suggesting subsequent movement of damaged muscle may contribute to variability. We hypothesized that immobilization decreases lymphatic transport of CK from damaged muscle, blunting the CK response. In this study, we compared changes in plasma CK and myoglobin (Mb), as Mb is released from damaged muscle directly into the bloodstream whereas CK is released first into the lymph.


METHODS
Twenty-five college-age males were matched according to force loss after 50 maximal eccentric contractions of the elbow flexors and placed into an immobilization (IMM, N = 12) or control (CON, N = 13) group. IMM had their arm immobilized at 90 degrees and secured in a sling for 4 d (treatment). Venipuncture was performed during baseline, treatment, and for 5 d after treatment (recovery) to assess plasma CK activity and Mb. Urine specific gravity (USG) and muscle activity (ACT) were assessed.


RESULTS
Immobilization significantly blunted increases in CK activity (IMM: 955 +/- 316 IU.L-1 vs CON: 2884 +/- 1083 IU.L-1; P < 0.05) but not increases in Mb (IMM: 712 +/- 278 ng.mL-1 vs CON: 891 +/- 253 ng.mL-1; P > 0.05). There were no differences in USG between groups over time (P > 0.05) and no group differences in ACT (P > 0.05).


CONCLUSIONS
Short-term immobilization after eccentric exercise blunted the CK response but not the Mb response, suggesting lymphatic transport of CK may be responsible. Because hydration status and muscular activity after exercise were not different between groups, the blunted CK response was likely due to inactivation of CK activity before entering circulation.
Human Physiology Laboratory, Department of Health Sciences, Boston University, Sargent College of Health and Rehabilitation Sciences, 635 Commonwealth Avenue, Boston, MA 02215, USA. ssayers@bu.edu
Stephen P
SP
Sayers
Pricilla M
PM
Clarkson
D000328:Adult; D000704:Analysis of Variance; D016022:Case-Control Studies; D003402:Creatine Kinase / Q000032:analysis / Q000378:metabolism*; D005080:Exercise Test; D006801:Humans; D007103:Immobilization; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018485:Muscle Fibers, Skeletal / Q000201:enzymology / Q000502:physiology; D009126:Muscle Relaxation / Q000502:physiology*; D018482:Muscle, Skeletal / Q000201:enzymology* / Q000502:physiology; D009211:Myoglobin / Q000032:analysis / Q000378:metabolism*; D011336:Probability; D012016:Reference Values; D012680:Sensitivity and Specificity; D013997:Time Factors
D009211:Myoglobin; D003402:Creatine Kinase