Differences in muscle strength, muscle soreness, and blood CK activity after eccentric exercise for ACTN3 gene polymorphism

Abstract

[Purpose] The purpose of this study was to examine the change of muscle damage markers after maximal eccentric exercise and to verify the difference of recovery according to ACTN3 gene polymorphism. [Methods] Fifty healthy males participated in this study. Subjects performed 25 times/1 set (total 2 set) maximal eccentric contractions of the elbow flexor muscles on a modified preacher curl machine with a between-sets rest time of 5 min. Maximal isometric contraction (MIC) was measured 6 times (pre, post, after 24 h, 48 h, 72 h and 96 h). Muscle soreness (SOR) was measured 5 times (pre, after 24 h, 48 h, 72 h and 96 h). Blood samples were collected 5 times (pre, after 24 h, 48 h, 72 h and 96 h). ACTN3 gene polymorphisms were identified using polymerase chain reaction (PCR). Data were analyzed using a 2-way repeated measure ANOVA and post hoc Bonferroni test. [Results] Analysis of ACTN3 gene polymorphism revealed the following distribution: 22% RR (n=11), 50% RX (n=25), and 28% XX (n=14). Individuals were classified into the RR homozygote group (n=11) and the X-allele group (n=39). MIC showed a significant difference between groups and interaction (p<.05). The groups differed significantly in MIC at 48 h, 72 h, and 96 h after exercise and the X-allele group decreased more than the RR homozygote group. The groups differed significantly in muscle soreness and interaction (p<.05). SOR in the X-allele group was significantly higher than in the RR homozygote group at 24 h after exercise. Although blood CK activity was lower in the RR homozygote group than in the X-allele group, but there was no significant difference between the groups (p>.05). [Conclusion] The RR homozygote group showed lower muscle strength reduction rate, muscle soreness and blood CK activity than the X-allele group. This indicates that RR individuals have a lower risk of exercise-induced muscle damage than those with an X-allele.