Evaluation of cardiorespiratory fitness using three field tests in obese adolescents: validity, sensitivity and prediction of peak VO2.

OBJECTIVES: Evaluation of cardiorespiratory fitness in obese adolescents is necessary to develop personalised retraining programmes. We aimed to measure cardiorespiratory fitness using 3 field tests, and to evaluate their validity and sensitivity compared to values obtained by laboratory tests. DESIGN: Longitudinal interventional study in obese adolescents admitted to a rehabilitation centre for a 9-month programme of obesity management. METHODS: A 12-min walk/run test, an adapted 20 m shuttle walk-run test (starting speed 4 km h(-1), increments of 0.5 km h(-1)min(-1)) and a 4-level submaximal cycle ergometer test were performed to estimate respectively distance covered in 12 min, maximum speed and maximal aerobic power. RESULTS: Thirty adolescents aged 14.2 ± 1.6 years were included. After 9 months intervention, we observed a significant reduction in body mass index, and an increase in peak VO2 and field test results. We observed significant correlations between pre- and post-intervention values of peak VO2 and distance covered in 12 min (r=0.70 pre; r=0.82 post), maximum speed (r=0.80 pre; r=0.83 post) and maximal aerobic power (r=0.71 pre; r=0.84 post). Multiple linear regression made it possible to estimate peak VO2 based on results from the 3 field tests using prediction equations specific to a population of obese adolescents. CONCLUSIONS: These field tests, including the adapted 20 m shuttle walk-run test, adequately assess cardiorespiratory fitness in obese adolescents, and are sensitive to changes over time. Predictive equations including BMI are useful in clinical practice to predict peak VO2 in these patients.