Influence of Muscle Fiber Composition and Muscle Cross-Sectional Area On Maximal Isometric Strength

Abstract

The purpose of the present study is to investigate the influence of muscle cross-sectional area on maximal isometric strength (M. I. S.), and the influence of muscle fiber composition on the ratio of maximal isometric strength to muscle cross-sectional area in the leg extensor muscles. Muscle biopsies were taken from the right vastus lateralis of 16 healthy untrained males. Cross-sectional area of the leg extensor muscles were measured by ultrasonic measurements. Maximal isometric strength were determined as peak torques using an isokinetic dynamometer. Significant positive correlation was observed between muscle cross-sectional area and maximal isometric strength (r=0.61, p<0.05). The ratio of maximal isometric strength to muscle cross-sectional area was 2.6±0.4 Nm/cm2 (mean ± S. D.) with a wide range of values from 2.0 to 3.3 Nm/cm2. No relationship was observed to exist between the ratio of maximal isometric strength to muscle cross-sectional area and muscle fiber composition. From these results it can be concluded that muscle cross-sectional area plays a more important role in producing a high maximal isometric strength than muscle fiber composition, and that the large variations observed in the ratio of maximal isometric strength to muscle cross-sectional area may be caused by factors other than muscle fiber composition. © 1986, The Japanese Society of Physical Fitness and Sports Medicine. All rights reserved.