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

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 (VO max), the "gold standard" for assessing aerobic exercise capacity, has not been previously described in PWS.

OBJECTIVES

Assess aerobic capacity by direct measurement of VO 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/m 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/m. All completed a medical questionnaire and performed strength and flexibility tests. VO max was determined by measuring oxygen consumption during a graded exercise test on a treadmill.

RESULTS

VO 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 VO max were almost identical for the OC group (p = 0.995), for the PWS group, both methods for estimating VO max gave values which were significantly greater (p < 0.001) than results obtained by direct measurements.

CONCLUSIONS

Aerobic capacity, assessed by direct measurement of VO max, is significantly lower in PWS adults, even in those who exercise daily, compared to OCs. Indirect estimates of VO max are accurate for OC, but unreliable in PWS. Direct measurement of VO should be used for designing personal training programs and in clinical studies of exercise in PWS.