Accurate assessment of cardiorespiratory fitness (CRF) in adolescents is critical. However, normalizing oxygen consumption (VO
2) to body mass (BM) may underestimate CRF in overweight (OW) youth by including metabolically inactive fat mass. This study examined differences in VO
2 normalized by BM and fat-free mass (FFM) between normal weight (NW) and OW adolescents. Thirty-eight participants (19 NW, 19 OW; 12–17 years) underwent anthropometric, body composition, and cardiorespiratory fitness assessments. VO
2 at the aerobic threshold (VO
2AerT), anaerobic threshold (VO
2AnT), and peak exercise (VO
2peak) were measured and expressed in absolute terms and relative to BM and FFM. Group differences in the main outcomes were analyzed using a one-way ANOVA, and Pearson correlation was used to examine associations between VO
2, BM and FFM. When normalized by BM, NW adolescents showed significantly higher VO
2AerT (18.7 ± 3.6 vs. 14.5 ± 2.3), VO
2AnT (28.8 ± 6.3 vs. 23.6 ± 4.7), and VO
2peak (37.7 ± 6.7 vs. 29.1 ± 7.0) compared to OW peers (
p < 0.05). No significant differences were found when VO
2 values were normalized by FFM. A group difference was observed in the VO
2peak vs. BM slope (
p = 0.03) but not in the VO
2peak vs. FFM slope. FFM normalization provides a more accurate assessment of CRF by accounting for differences in body composition, underscoring the importance of evaluating the aerobic capacity of metabolically active tissue rather than total body weight in youth populations.
Full article