Physical activity and maximal oxygen uptake in adults with Prader-Willi syndrome

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.

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.

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.

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.

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.