Relationship between body composition and cardiorespiratory fitness in Japanese junior high school boys and girls

This study attempted to evaluate the influence of body composition on cardiorespiratory fitness as represented by maximal oxygen uptake (VO2max) in junior high school boys and girls. The subjects were judged apparently healthy. Measurements of VO2max during an incremental treadmill exercise testing as well as measurements of body composition were compared between obese boys and girls, 12 to 15 years old, and age- and height-matched nonobese boys and girls. Analyses of the data revealed that statistically significant (P < 0.01) mean differences between the obese and nonobese groups were observed for body mass (BM), percentage body fat, and body fat content. Fat-free mass (FFM) of obese boys was significantly larger than nonobese boys. There were significant differences between obese and nonobese groups irrespective of sex, when VO2max was expressed as milliliters of oxygen per kilogram of BM per minute. In contrast, no significant group differences were found in VO2max expressed as ml per kg of FFM per min. No significant differences existed either for absolute VO2max between the obese girls and the nonobese girls due almost entirely to the similarity in FFM between these two groups. Significant correlations were found both in boys (r = -0.742) and girls (r = -0.843) between VO2max (ml/kg BM/min) and percentage body fat, thereby indicating the striking effects of excess body fat. These results in the present study support the general belief that obesity accentuates exercise intolerance and low aerobic capacity.