Body Weight As A Determinant Of Exercise Capacity In Overweight Adolescents

Abstract

Excess bodyweight may increase the metabolic cost of work and diminish physical activity tolerance. PURPOSE: To determine the influence of excess bodyweight on exercise capacity in adolescents who were overweight. METHODS: Subjects were 30 (16 females and 14 males) normal weight (NW),(height: 1.6±0.1 m, weight: 55.5±12.1 kg) and 63 (45 females and 18 males) overweight (OW) (height: 1.7±0.1 m, weight: 107.5±20.3 kg) adolescents. The NW and OW groups were 14.5±1.7 years and 14.8±1.4 years of age respectively. Oxygen uptake (VO2) was first measured during unloaded cycling (ULVO2). Subjects then completed a maximum cycle ergometer test to exhaustion. Maximum VO2, and power output (Wmax) were measured. The change in VO2 from unloaded cycling to maximum exercise (NetVO2) was calculated as the difference between VO2 max and ULVO2. Group differences in the dependent variables were determined by Student‘s t tests. A Pearson product moment coefficient of determination (r2) was used to characterize the relationship between ULVO2 and body weight (BW) and Wmax and NetVO2. RESULTS: VO2max was similar for NW (2067±571 mlO2/min) and OW (2041±481 mlO2/min). ULVO2 in OW (693±169 mlO2/min) was significantly (p<0.001) higher than in NW (406±125 mlO2/min) and significantly related to BW (r2=0.63, p<0.0001). Wmax (185±44 in NW vs 153±34watts in OW; p<0.001) and NetVO2 (1661±495 in NW vs 1348±427 mlO2/min in OW; p<0.004) were significantly lower in OW than in NW. Wmax and NetVO2 were determinately related (r2=0.85, p<0.001). Wmax and NetVO2 were 17.3% and 18.8 % lower in OW than in NW. CONCLUSION: The gender make-up of the NW and OW groups was disproportional. Nonetheless, the very high coefficient of determination, combined with the close proportionality between the reduction in NetVO2 and Wmax, suggested that the increased metabolic cost of work was likely the cause of the reduced exercise capacity in these adolescents who were overweight.