Abstract
Myosin light chain kinase (MLCK) phosphorylates the regulatory light chain (RLC) of myosin producing increases in force development during skeletal muscle contraction. It has been suggested that MLCK gene polymorphisms might alter RLC phosphorylation thereby decreasing the ability to produce force and to resist strain during voluntary muscle contractions. Thus, the genetic variations in the MLCK gene might predispose some individuals to higher values of muscle damage during exercise, especially during endurance competitions. The aim of this investigation was to determine the influence of MLCK genetic variants on exercise-induced muscle damage produced during a marathon. Sixty-seven experienced runners competed in a marathon race. The MLCK genotype (C37885A) of these marathoners was determined. Before and after the race, a sample of venous blood was obtained to assess changes in serum myoglobin concentrations and leg muscle power changes were measured during a countermovement jump. Self-reported leg muscle pain and fatigue were determined by questionnaires. A total of 59 marathoners (88.1%) were CC homozygotes and 8 marathoners (11.9%) were CA heterozygotes. The two groups of participants completed the race with a similar time (228 ± 33 vs 234 ± 39 min; P = 0.30) and similar self-reported values for fatigue (15 ± 2 vs 16 ± 2 A.U.; P = 0.21) and lower-limb muscle pain (6.2 ± 1.7 vs 6.6 ± 1.8 cm; P = 0.29). However, CC marathoners presented higher serum myoglobin concentrations (739 ± 792 vs 348 ± 144 μg·mL-1; P = 0.03) and greater pre-to-post- race leg muscle power reduction (-32.7 ± 15.7 vs -21.2 ± 21.6%; P = 0.05) than CA marathoners. CA heterozygotes for MLCK C37885A might present higher exercise-induced muscle damage after a marathon competition than CC counterparts.
Highlights
During skeletal muscle contraction, two small protein subunits, the essential light chain and phosphorylatable regulatory light chain (RLC) of myosin facilitate the formation of cross-bridges between the sarcomeric proteins actin and myosin
Homozygosis presented higher muscle performance decrements after the marathon than CA heterozygotes, as measured by pre-to-post-race changes in leg muscle power production and jump height during a countermovement jump (Fig 1); CC homozygotes showed higher post-race serum myoglobin concentrations than CA heterozygotes (Fig 2) serum creatine kinase concentration was not different between groups at the end of the race; c) there were no between-group differences in the self-reported values of muscle pain or perceived exertion while both groups for runners maintained a similar steady-state running pace during the race. These results indicate that the presence of CC homozygosis for Myosin light chain kinase (MLCK) C37885A might predispose amateur runners to higher levels of exercise-induced muscle damage
This increased predisposition was resolved without any clinical consequences because no participant in this investigation developed an episode of exertional rhabdomyolysis
Summary
Two small protein subunits, the essential light chain and phosphorylatable regulatory light chain (RLC) of myosin facilitate the formation of cross-bridges between the sarcomeric proteins actin and myosin. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
