Juozas Baltusnikas, Tomas Venckunas, Audrius Kilikevicius, Andrej Fokin, Aivaras Ratkevicius
Journal of Sports Science and Medicine
Elevated plasma creatine kinase (CK) activity is often used as an indicator of exercise-induced muscle damage. Our aim was to study effects of contraction type, sex and age on CK efflux from isolated skeletal muscles of mice. The soleus muscle (SOL) of adult (7.5-month old) female C57BL/6J mice was subjected to either 100 passive stretches, isometric contractions or eccentric contractions, and muscle CK efflux was assessed after two-hour incubation in vitro. SOL of young (3-month old) male and female mice was studied after 100 eccentric contractions. For adult females, muscle CK efflux was larger (p < 0.05) after eccentric contractions than after incubation without exercise (698 ± ۳۴۴ vs. 268 ± ۱۸۴ mU·h−۱, respectively), but smaller (p < 0.05) than for young females after the same type of exercise (1069 ± ۳۴۱ mU·h−۱). Eccentric exercise-induced CK efflux was larger in muscles of young males compared to young females (2046 ± ۳۱۷ vs 1069 ± ۳۴۱ mU · h−۱, respectively, p < 0.001). Our results show that eccentric contractions induce a significant increase in muscle CK efflux immediately after exercise. Isolated muscle resistance to exercise-induced CK efflux depends on age and sex of mice.
Key words: Skeletal muscle, eccentric contractions, muscle damage, CK activity