Ethnicity affects aerobic fitness in U.S. adolescent girls

PIVARNIK, J. M., M. S. BRAY, A. C. HERGENROEDER, R. B. HILL, and W. W. WONG. Ethnicity affects aerobic fitness in U.S. adolescent girls. Med. Sci. Sports Exerc., Vol. 27, No. 12, pp. 1635–1638, 1995. The purpose of this investigation was to determine whether aerobic fitness (V̇O2max) differed between black (N = 40) and white (N = 53) adolescent girls who were similar in age (13.5 yr) and percent body fat (24.6%). Expired gases were collected continuously while each girl performed a standard Bruce protocol to volitional exhaustion on a motorized treadmill (TM). Heart rates (HR) were measured during the exercise testing via telemetry. Fat-free mass (FFM) was estimated with total body electrical conductivity (TOBEC). Average (±SD) maximum HR (black = 194 ± 7; white = 198 ± 8) and respiratory exchange ratios (black = 1.17 ± 0.08; white = 1.22 ± 0.09) did not differ between subject groups. Aerobic fitness was significantly (P < 0.01) lower in black versus white girls when V̇O2max was expressed relative to body weight (31.8 ± 5.8 vs 38.5 ± 6.8 ml·kg-1·min-1) and body weight raised to the 0.67 power (120.9 ± 19.5 vs 138.5 ± 20.7 ml·kg-0.67min-1). Treadmill time to exhaustion was significantly less (P < 0.01) in the black (8.49 ± 1.30 min) versus white (9.41 ± 1.60) subjects. Also, black subjects demonstrated less ability to utilize O2 during maximal exercise at a given FFM. This suggests the black girls' FFM contained a smaller percentage of skeletal muscle mass that could be utilized during treadmill exercise. It is possible that lower aerobic fitness values seen in the black girls are related to a combination of anatomical, physiological and/or behavioral factors.