Influence of Age on Isometric, Isotonic, and Isokinetic Force Production Characteristics in Men

Abstract

2437 Most previous research have focused on the effects of age on force production characteristics of a single contraction type (isometric, isokinetic, or isotonic) and usually a single muscle group. PURPOSE: The purpose of this study was to investigate the influence of chronological age on isometric, isotonic, and isokinetic force production characteristics of four muscle groups in normal, healthy men aged 20–83 years. A second objective was to determine relationships between regional lean body mass and the force production characteristics examined. METHODS: Seventy five volunteers were placed into designated 10-year age groups: 20–29 (n = 13); 30–39 (n = 14); 40–49 (n = 15); 50–59 (n = 10); 60–69 (n = 14); and 70+ years (n = 9). Muscle function was characterized by a number of parameters (strength, time, rate, etc) for all three contraction types (isometric, isokinetic, isotonic) and four muscle groups (elbow extensors, elbow flexors, knee extensors, and knee flexors). Measures of lean body mass were obtained by DXA. RESULTS: There were significant age group differences in the ability to produce maximal force (strength) (p < 0.05) for each type of muscle contraction, and to generate maximal rates of isometric force production (p < 0.05), with an overall decline beginning around 60 years of age. The differences that were observed in force production capabilities between age groups remained when body composition differences were statistically controlled. CONCLUSION: Chronological age did affect force production parameters of both upper and lower extremity muscles, regardless of contraction type, however, isometric strength was not affected as much as isokinetic and isotonic measures. Additionally, differences in muscle function with increasing age could not be explained by differences in muscle mass.