Human alpha-actinin-3 genotype association with exercise-induced muscle damage and the repeated-bout effect

Abstract

26Alpha-actinin-3 (ACTN3) is an integral part of the Z-line of the sarcomere. The ACTN3 R577X 27 (rs1815739) polymorphism determines the presence or absence of functional ACTN3 which may 28 influence the extent of exercise induced muscle damage. This study aimed to compare the impact of, 29 and recovery from, muscle-damaging eccentric exercise on subjects with or without functional alpha-30 actinin-3. Seventeen young men (20-33 years), homozygous for the R-(n=9) or X-(n=8) alleles, 31 performed two bouts of stretch-shortening exercise (50 drop jumps) 2 weeks apart. Muscle soreness, 32 plasma creatine kinase (CK) activity, jump height, maximal voluntary isometric torque (MVC), peak 33 concentric isokinetic torque (IT), and electrically stimulated knee extension torques at 20 Hz and at 34 100 Hz were measured at baseline and a number of timepoints up to 14 days after each bout. There 35 were no significant baseline differences between the groups. However, significant 36 timepoint*genotype interactions were observed for MVC (p=0.021) and IT (p=0.011) for the 37 immediate effect of eccentric exercise in bout 1. The RR group showed greater voluntary force 38 decrements (RR v XX, MVC: -33.3% v -24.5%, IT: -35.9% v -23.2%) and slower recovery. A 39 repeated bout effect was clearly observed but there were no differences by genotype group. ACTN3 40 genotype modulates the response of muscle function to plyometric jumping exercise, although the 41 differences are modest. ACTN3 genotype does not influence the clearly observed repeated bout 42 effect; however, XX homozygotes recover baseline voluntary torque values faster and thus may be 43 able to undertake more frequent training sesssions. 44 45

Greater muscle damage in athletes with ACTN3 R577X (RS1815739) gene polymorphism after an ultra-endurance race: a pilot study

“…Venckunas et al [32] found that RR genotype individuals had a greater voluntary force decrement and slower recovery than XX genotype, after a drop jump exercise session (40 cm x 50 repetitions), with no difference for plasma CK activity. Clarkson et al [18] found no association between ACTN3 R577X (rs1815739) gene polymorphism and increases in CK and Mb levels, after 50 maximal eccentric contractions of the elbow flexor muscles.…”

“…Clarkson et al [18] found no association between ACTN3 R577X (rs1815739) gene polymorphism and increases in CK and Mb levels, after 50 maximal eccentric contractions of the elbow flexor muscles. These contradictory results may be explained as a result of the heterogeneity of the population studies and the training status, since neither study investigated well-trained individuals [18, 32]. Other gene polymorphisms have also been associated with muscle damage [33–35], and the interaction effect between two or more gene polymorphisms on muscle damage susceptibility can better clarify this response.…”

Effects of Estrogen Fluctuation during the Menstrual Cycle on the Response to Stretch-Shortening Exercise in Females

“…In humans, the extent of muscle damage differs between individuals and can be explained by different factors such as the type and intensity of exercise and the person's age, fitness level, and genotype [8–10]. Sex differences and, more precisely, hormonal differences may influence the extent of damage and recovery in muscles.…”

The Effect of Three Different Strategies Based on Motor Task Performance on Neuromuscular Fatigue in Healthy Men and Men with Multiple Sclerosis

“…Peak torques induced by 1 s of electrical stimulation at 20 Hz (P20; representing the steep section of the force–frequency relationship curve) and 100 Hz (P100; which is close to the maximal force) were measured with a 3 s rest interval between electrical stimulations [22,24]. The change in the P20 to P100 ratio (P20/P100) was used as a proxy of low-frequency fatigue [25]. The tolerance to electrical stimulation was evaluated during the introduction session, and only participants who exhibited good compliance with the procedure were employed in the study.…”