Age-Related Variability in Single Muscle Fiber Contractile Properties

Abstract

1397 The biological process of aging has been associated with an increased variability in physiological functions. PURPOSE: To assess the effect of age on variability of single muscle fiber isometric contractile properties in a large population of healthy adults. METHODS: Percutaneous biopsies were obtained from the vastus lateralis of 73 subjects classified by age and gender into 4 groups: young males (YM: n = 8, mean age 37 yrs), older males (OM: n = 20, mean age 70), young females (YF: n = 10, mean age 29), and older females (OF: n = 35, mean age 60). Cross sectional area (CSA), peak isometric tension (Po), and maximum unloaded shortening velocity (Vo) were measured in 1671 chemically skinned single muscle fibers. Vo was determined using the slack test. Myosin heavy chain isoform expression was identified using SDSPAGE. Descriptive statistics were performed by fiber type, age, and gender. Standard deviation was used as a measure of variability for each parameter. RESULTS: In older adults, variability increases for CSA, decreases for Po, and shows no consistent trend for Vo.Table: No Caption available.n = number of single fibers CONCLUSION: This data set characterizes the variability in single muscle fiber contractile properties of a large population of healthy individuals. With age, variation in single muscle fiber size increases, but there is not an accompanying increase in variability of contractile properties.