Vo2max Relationship To Fat Free Mass Estimates From Skinfolds In Athletes And Sedentary Subjects

A strong correlation between maximal oxygen consumption (VO2max) and fat free mass (FFM) reflects the relationships between muscle, the major component of FFM, and the oxygen delivery systems. Aerobic training can alter these relationships. PURPOSE: To characterize differences in VO2max and FFM in Kuwaiti subjects participating regularly in sports compared to sedentary subjects. METHODS Subjects were adult males athletes (n=85, means ±SD: 26.2±4.2 years, 175.4±7.4 cm height) or healthy sedentary urban office workers or students reporting no regular physical activity in the last six months (n=61, 31±7.4 years, 170.7±6.4 cm height). Sports were classified according to their aerobic component: long distance swimming or running (0.8), tennis (0.7), soccer referee (0.6), water-polo (0.6), soccer (0.5), handball (0.5), basketball (0.4), fencing (0.4), karate (0.4), or weight training (0.1). Bruce's treadmill protocol was used to measure VO2max. Mid trunk flexibility was measured (cm) using a sit and reach instrument (Lafayette Co.). Height, weight (Detecto), and seven skin-fold thickness (John Bull caliper) were measured in all participants by a single investigator (JR) and used to estimate body density (Jackson et al., 1980) and FFM. All subjects signed informed consent prior to testing. RESULTS: The positive correlation (R2=0.34, p<0.01) between FFM, (67±8.7 Kg FFM) estimated from skin-folds, and VO2max (4±0.68 L/min) in physically active subjects was absent (R2= 0.19, p>0.05) in sedentary subjects (61.9±7.1 Kg FFM, VO2max 3.2±0.66 L/min). Stepwise multiple regression analysis indicated that VO2max was predicted (R2=0.48) as 0.255+0.048 (FFM)-0.12 (Resting Heart Rate)+2.1(Aerobic Component of Sport)+0.015(Flexibility) in athletes but not in sedentary subjects (R2=0.23) where VO2max=2.68+ 0.24(Flexibility). CONCLUSIONS: Skin-fold based FFM estimates are a less reliable reflection of muscle mass in sedentary than in athletic subjects. In addition, local factors such as joint flexibility, pain and fatigue have more of an influence on peak oxygen uptake in sedentary than in physically active subjects, in spite of similar efforts to reach maximal activity as judged by the maximal heart rates and high respiratory exchange ratios reached by both groups.