Effect of obesity onset on pendular energy transduction at spontaneous walking speed: Prader-willi versus nonsyndromal obese individuals

Objective To compare the mechanical external work (Wext) and pendular energy transduction (Rstep) at spontaneous walking speed (Ss) in individuals with Prader-Willi syndrome (PWS) versus subjects with nonsyndromal obesity (OB) to investigate whether the early onset of obesity allows PWS subjects to adopt energy conserving gait mechanics. Design and Methods Wext and Rstep were computed using kinematic data acquired by an optoelectronic system and compared in 15 PWS (BMI = 39.5 +/- 1.8 kg m-2; 26.7 +/- 1.5 year) and 15 OB (BMI = 39.3 +/- 1.0 kg m-2; 28.7 +/- 1.9 year) adults matched for gender, age and BMI and walking at Ss. Results Ss was significantly lower in PWS (0.98 +/- 0.03 m s-1) than in OB (1.20 +/- 0.02 m s-1; P < 0.001). There were no significant differences in Wext per kilogram between groups (PWS: 0.37 +/- 0.04 J kg-1 m-1; OB: 0.40 +/- 0.05 J kg-1 m-1; P = 0.66) and in Rstep (PWS: 69.9 +/- 2.9%; OB: 67.7 +/- 2.4%; P = 0.56). However, Rstep normalized to Froude number (Rstep/Fr) was significantly greater in PWS (6.0 +/- 0.6) than in OB (3.8 +/- 0.2; P = 0.001). Moreover, Rstep/Fr was inversely correlated with age of obesity onset (r = -0.49; P = 0.006) and positively correlated with obesity duration (r = 0.38; P = 0.036). Conclusion Individuals with PWS seem to alter their gait to improve pendular energy transduction as a result of precocious and chronic adaptation to loading.