Oxygen-uptake efficiency slope as a determinant of fitness in overweight adolescents

PURPOSE: Peak oxygen uptake (V̇O2peak) is frequently difficult to assess in overweight individuals; therefore, submaximal measures that predict V̇O2peak are proposed as substitutes. Oxygen uptake efficiency slope (OUES) has been suggested as a submaximal measurement of cardiorespiratory fitness that is independent of exercise intensity. There are few data examining its value as a predictor of V̇O2peak in severely overweight adolescents. METHODS: One hundred seven severely overweight (BMI Z 2.50 ± 0.34) and 43 nonoverweight (BMI Z 0.13 ± 0.84) adolescents, performed a maximal cycle ergometer test with respiratory gas-exchange measurements. OUES was calculated through three exercise intensities: lactate inflection point (OUES LI), 150% of lactate inflection point (OUES 150), and V̇O2peak (OUES PEAK). RESULTS: When adjusted for lean body mass, V̇O2peak and OUES at all exercise intensities were lower in overweight subjects (V̇O2peak: 35.3 ± 6.4 vs 46.8 ± 7.9 mL·kg LBM·min, P < 0.001; OUES LI: 37.9 ± 10.0 vs 43.7 ± 9.2 mL·kg LBM·min·logL P < 0.001; OUES 150: 41.6 ± 9.0 vs 49.8 ± 11.1 mL·kg LBM·min·logL P < 0.001; and OUES PEAK: 45.1 ± 8.7 vs 52.8 ± 9.6 mL·kg LBM·min·logL P < 0.001). There was a significant increase in OUES with increasing exercise intensity in both groups (P < 0.001). OUES at all exercise intensities was a significant predictor of V̇O2peak for both groups (r = 0.35-0.83, P < 0.0001). However, limits of agreement for predicted V̇O2peak relative to actual V̇O2peak were wide (± 478 to ± 670 mL·min). CONCLUSIONS: OUES differs significantly in overweight and nonoverweight adolescents. The wide interindividual variation and the exercise intensity dependence of OUES preclude its use in clinical practice as a predictor of V̇O2peak.