Validation of a new scale to measure perceived exertion in obese adolescents: the Childhood Obesity Perceived Exertion (Cope-10) Scale.

BACKGROUND: The aim of this study was to validate a measurement scale for perceived exertion, named the Childhood Obesity Perceived Exertion Scale (COPE-10), by evaluating concurrent validity, reliability and sensitivity in obese adolescents. METHODS: Thirty obese adolescents (BMI 36.2±0.8 kg.m-2), aged 14.2±0.3 years, performed two incremental exercise tests (maximal followed by submaximal) before and after a multidisciplinary obesity management program. To standardize workload, physiological variables [heart rate (HR), ventilation (E) and gas exchange (O2)] and perceived exertion (RPE) were modelized (fHR, fVE, fVO2, fRPE). At a rank of 6 on the COPE-10 Scale (RPE6) and at fixed second ventilatory threshold (VT2), we determined respectively the associated power (WPRPE6, WPVT2) and HR (HRRPE6, HRVT2). RESULTS: During maximal exercise, we observed significant correlations between fRPE and each of fHR (r=0.88 ; r=0.91), fVE (r=0.93 ; r=0.94) and fVO2 (r=0.87 ; r=0.89) before and after management respectively, indicating the concurrent validity of the COPE-10 Scale to estimate exercise intensity in obese adolescents. During submaximal exercise, we observed intraclass correlation coefficients of 0.77 before and 0.86 after management, showing reliability. After management, WPVT2 and WPRPE6 increased significantly (+23W and +21W ; P<0.001), and there was a significant correlation between HRVT2 and HRRPE6 (r=0.90), illustrating the scale's sensitivity to change. CONCLUSIONS: The COPE-10 Scale is a valid tool to measure perceived exertion in obese adolescents. This inexpensive and non-invasive instrument could be widely used in rehabilitation programs for obese youths.

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.

Ghrelin and PYY levels in adolescents with severe obesity: effects of weight loss induced by long-term exercise training and modified food habits.

This study investigated (a) changes in ghrelin and peptide YY (PYY) concentrations during a weight reduction programme and (b) baseline ghrelin and PYY levels as predictors of weight loss in 32 severely obese adolescents (BMI z score = 4.1). Subjects spent an academic year in an institution for childhood obesity. Fasting ghrelin and PYY, leptin, insulin levels and insulin resistance were measured at baseline (month 0) and during the programme (months 3, 6, 9). In addition, 15 normal-weight teenagers served as reference for the baseline assessments. At baseline, obese teenagers had lower ghrelin and PYY concentrations than normal-weight adolescents (P < 0.05). Moreover, they showed significantly higher leptin, insulin levels and homeostasis model assessment (HOMA) (P < 0.0001). During the lifestyle modification, there was a significant decrease in body weight among obese teenagers, associated with an increase in ghrelin (apparent from month 6; P < 0.05), a decrease in leptin (from month 3; P < 0.05) and a decrease in insulin and HOMA (from month 3; P < 0.0001), without any significant change in PYY. Anthropometrical changes were correlated neither with baseline ghrelin levels nor with changes in ghrelin and PYY after the lifestyle modification. However, higher baseline PYY tended to correlate with greater anthropometrical changes (P < 0.1). In adolescents with severe obesity, a long-term combination of supervised aerobic exercises and a balanced diet led to weight reduction and increased ghrelin concentrations, without any change in PYY concentrations. Moreover, baseline PYY concentrations might be considered as predictors of weight loss.