Strength and cross‐sectional area of human skeletal muscle.

Abstract

SUMMARY1. The maximum voluntary force (strength) which could be produced by the knee-extensor muscles, with the knee held at a right angle, was measured in a group of healthy young subjects comprising twenty-five males and twenty-five females. Both legs were tested: data from the stronger leg only for each subject were used in the present study.2. Computed tomography was used to obtain a cross-sectional image of the subjects' legs at mid-thigh level, measured as the mid-point between the greater trochanter and upper border of the patella. The cross-sectional area of the kneeextensor muscles was determined from the image obtained by computer-based planimetry.3. The subjects' height and weight were measured. An estimate of body fat content was obtained from measurements of skinfold thicknesses and used to calculate lean body mass.4. Male subjects were taller (P < 0-001), heavier (P < 0-001), leaner (P < 0-001) and stronger (P < 0-001) than the female subjects. No significant correlation was found to exist between strength of the knee-extensor muscles and body weight in the male or in the female subjects. In the male subjects, but not in the female group, there was a positive correlation (r = 0 50; P < 0-01) between strength and lean body mass.5. Muscle cross-sectional area of the male subjects was greater than that of the female subjects (P < 0-001). The ratio of strength to cross-sectional area for the male was 9-49 + 1-34 (mean + S.D.). This is greater but not significantly so, than that for females (8-92+ 1 11). In both male and female groups, there was a significant (P < 0-01) positive correlation between muscle strength and cross-sectional area.6. A wide variation in the ratio of strength to muscle cross-sectional area was observed. This variability may be a result of anatomical differences between subjects or may result from differences in the proportions of different fibre types in the muscles. The variation between subjects is such that strength is not a useful predictive index of muscle cross-sectional area.

Gender differences in strength and muscle fiber characteristics

“…A similar gender difference in fiber number was observed in the tibialis anterior (Henriksson-Larsen 1985). A number of investigators have reported that the strength/GSA ratio is greater in males than in females (Morris 1948;Young et al 1985;Ryushi et al 1988), however, considerable variation exists within each gender (Maughan et al 1983;Maughan & Nimmo). Differences in limb lengths (McCullagh et al 1984) and the connective tissue volume density (Sale et al 1987) probably account for some of the variability in the strength/GSA ratio between and within genders.…”

“…The finding that strength and muscle cross-sectional area (GSA) are highly correlated (Ikai & Fukunaga 1968;Maughan et al 1983;Maughan & Nimmo 1984) and that the strength to GSA ratio is similar for males and females (Ikai & Fukunaga 1968;Schantz et al 1983;Sale et al 1987) …”

“…It is, however, important to note that large inter-individual differences in the strength to CSA ratio have also been observed within each gender, suggesting that the factors responsible for the variability in the ratio may not be gender specific (Maughan et al 1983;Maughan & Nimmo 1984).…”

Evidence of Reduced Muscle Trauma Through a Minimally Invasive Anterolateral Approach by Means of MRI

“…The use of nonferromagnetic titanium prostheses and ceramic balls instead of metal heads, as well as the observances of some technical features, eg, the orientation of the frequency-encoding gradient of the MR system, enables high-quality MRI of patients with THA. The changes in muscle cross-sectional area (CSA) and fatty atrophy of the muscle that can thus be visualized reflect the muscle damage and correlate with muscle function [28,29].…”

Changes of functional status and volume of triceps brachii measured by magnetic resonance imaging after maximal resistance training

“…IF THE STRENGTH of a muscle is to be properly related to its size, the physiological cross-sectional area (CSA) should be measured (1). In vivo, the physiological CSA of a muscle is linearly correlated with its volume (2,3), so a volumetric assessment will offer a surrogate measure of physiological significance.…”