ETHNICITY AFFECTS AEROBIC FITNESS IN US ADOLESCENT GIRLS

The purpose of this investigation was to determine whether aerobic fit ness (VO2max) differed between black (N = 40) and white (N = 53) adole scent girls who were similar in age (13.5 yr) and percent body fat (24 .6%). Expired gases were collected continuously while each girl perfor med a standard Bruce protocol to volitional exhaustion on a motorized treadmill (TM). Heart rates (HR) were measured during the exercise tes ting via telemetry. Fat-free mass (FFM) was estimated with total body electrical conductivity (TOBEC). Average (+/-SD) maximum HR (black = 1 94 +/- 7; white = 198 +/- 8) and respiratory exchange ratios (black = 1.17 +/- 0.08; white = 1.22 +/- 0.09) did not differ between subject g roups. Aerobic fitness was significantly (P < 0.01) lower in black ver sus white girls when VO2max 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(-0.67). m in(-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) subject s. Also, black subjects demonstrated less ability to utilize O-2 durin g maximal exercise at a given FFM. This suggests the black girls' FFM contained a smaller percentage of skeletal muscle mass that could be u tilized during treadmill exercise. It is possible that lower aerobic f itness values seen in the black girls are related to a combination of anatomical, physiological and/or behavioral factors.