The profile and distribution of myosin heavy chain isoforms in middle-aged sedentary persons

AIM: Human lifestyle has drastically changed during the past century as the share of physical work in daily life has decreased. The purpose of the present study was to examine the distribution of myosin heavy chain (MHC) isoforms in middle-aged sedentary persons, to compare the proportion of MHC isoforms of middle-aged and young sedentary persons and to demonstrate the effect of physical activity of MHC isoforms in middle-aged sedentary persons. METHODS: Eighty-nine middle-aged sedentary and 13 young sedentary persons volunteered for the study. Thirty middle-aged sedentary subjects participated in strength-conditional exercise program during 9 months. Vertical jumping height and maximal anaerobic work capacity were measured. Muscle samples were taken from vastus lateralis muscle. MHC isoform composition was determined by SDS-PAGE. RESULTS: Variation of MHC I and MHC IIa isoforms in middle-age sedentary persons demonstrated normal distribution. Significant differences of MHC isoform proportions between middle-aged and young sedentary participants were not observed. The proportion of MHC IIx decreased significantly after the exercise period that significantly improved the maximal anaerobic power and jumping height of participants. CONCLUSIONS: Normal distribution illustrated the proportion of MHC I and MHC IIa isoforms in 89 middle-aged sedentary persons while significant differences of MHC isoforms proportion between young and middle-aged sedentary persons were not observed. Even small increase of physical activity improved physical performance and decrease the MHC IIx proportion of middle-aged sedentary persons. Physically active lifestyle in middle age, when age-related changes have not started yet, may delay age-related changes in skeletal muscle.