ABSTRACT
BACKGROUND: Prader-Willi Syndrome (PWS) is the most common genetic syndrome causing life-threatening obesity. Strict adherence to a low-calorie diet and regular physical activity are needed to prevent weight gain. Direct measurement of maximal oxygen uptake (VO2 max), the "gold standard" for assessing aerobic exercise capacity, has not been previously described in PWS. OBJECTIVES: Assess aerobic capacity by direct measurement of VO2 max in adults with PWS, and in age and BMI-matched controls (OC), and compare the results with values obtained by indirect prediction methods. METHODS AND PATIENTS: Seventeen individuals (12 males) age: 19-35 (28.6 ± 4.9) years, BMI: 19.4-38.1 (27.8 ± 5) kg/m2 with genetically confirmed PWS who exercise daily, and 32 matched OC (22 males) age: 19-36 (29.3 ± 5.2) years, BMI: 21.1-48.1 (26.3 ± 4.9) kg/m2. All completed a medical questionnaire and performed strength and flexibility tests. VO2 max was determined by measuring oxygen consumption during a graded exercise test on a treadmill. RESULTS: VO2 max (24.6 ± 3.4 vs 46.5 ± 12.2 ml/kg/min, p < 0.001) and ventilatory threshold (20 ± 2 and 36.2 ± 10.5 ml/kg/min, p < 0.001), maximal strength of both hands (36 ± 4 vs 91.4 ± 21.2 kg, p < 0.001), and flexibility (15.2 ± 9.5 vs 26 ± 11.1 cm, p = 0.001) were all significantly lower for PWS compared to OC. Predicted estimates and direct measurements of VO2 max were almost identical for the OC group (p = 0.995), for the PWS group, both methods for estimating VO2 max gave values which were significantly greater (p < 0.001) than results obtained by direct measurements. CONCLUSIONS: Aerobic capacity, assessed by direct measurement of VO2 max, is significantly lower in PWS adults, even in those who exercise daily, compared to OCs. Indirect estimates of VO2 max are accurate for OC, but unreliable in PWS. Direct measurement of VO2 should be used for designing personal training programs and in clinical studies of exercise in PWS.
