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

Purpose: Peak oxygen uptake ((V) over dot O-2peak) is frequently difficult to assess in overweight individuals; therefore, submaximal measures that predict (V) over dot O-2peak 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 (V) over dot O-2peak 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 (V) over dot O-2peak (OUES PEAK). Results: When adjusted for lean body mass, (V) over dot O-2peak and OUES at all exercise intensities were lower in overweight subjects ((V) over dot O-2peak: 35.3 +/- 6.4 vs 46.8 +/- 7.9 mL.kg(-1) LBM.min(-1), P < 0.001; OUES LI: 37.9 +/- 10.0 vs 43.7 +/- 9.2 mL.kg(-1) LBM.min(-1).logL(-1) P < 0.001; OUES 150: 41.6 +/- 9.0 vs 49.8 +/- 11.1 mL.kg(-1) LBM.min(-1).logL(-1) P < 0.001; and OUES PEAK: 45.1 +/- 8.7 vs 52.8 +/- 9.6 mL-kg(-1) LBM.min(-1).logL(-1) 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 (V) over dot O-2peak for both groups (r(2) = 0.35-0.83, P < 0.0001). However, limits of agreement for predicted (V) over dot O-2peak relative to actual (V) over dot O-2peak were wide (+/-478 to +/-670 mL.min(-1)). 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 (V) over dot O-2peak.