Body Composition by DEXA and Its Association With Physical Fitness in 140 Conscripts

Abstract

The aim of the study was to determine the body composition of healthy young men and to investigate whether there exists an association between body composition and physical fitness. A prospective cohort study of 140 healthy male conscripts (mean age 19.8yr, SD 1.0 yr) was conducted. We examined subject characteristics, aerobic performance, and muscle strength, and we assessed body composition using dual-energy x-ray absorptiometry (DEXA). The association between total body composition and lower-limb composition and physical performance was investigated by linear regression. The mean body mass index (BMI) of the subjects was 24.6 kg.m (SD 4.7). Their mean bone mineral density (BMD) was 1.3 g.cm (SD 0.1), fat percentage (fat%) 22.6 (SD 9.7), lean mass 57.6 kg (SD 7.0), and bone mass 3.2 kg (SD 0.4) at the beginning of the military service. Fat percentage was significantly associated with 12-min running performance (P < 0.001), and a significant relationship was found between muscle strength and fat% (P< 0.001), and increasing BMD (P < 0.001), in multivariate analysis. Lean mass was not associated with physical performance. DEXA measurement of the proportion of body fat is a useful tool to indirectly assess running performance and muscle strength in Finnish male conscripts. Increased fat mass and fat percentage were strong predictors of poorer physical fitness. Moreover, the relationship between muscle strength and BMD was confirmed. However, muscle mass did not predict muscle strength in our sample.