Mechanical External Work and Recovery at Preferred Walking Speed in Obese Subjects

MALATESTA, D., L. VISMARA, F. MENEGONI, M. GALLI, M. ROMEI, and P. CAPODAGLIO. Mechanical External Work and Recovery at Preferred Walking Speed in Obese Subjects. Med. Sci. Sports Exerc., Vol. 41, No. 2, pp. 426-434, 2009. Purpose: The aim of this study was to compare the mechanical external work (per kilogram) and pendular energy transduction at preferred walking speed (PWS) in obese versus normal body mass subjects to investigate whether obese adults adopt energy conserving gait mechanics. Methods: The mechanical external work (W-ext) and the fraction of mechanical energy recovered by the pendular mechanism (R-step) were computed using kinematic data acquired by an optoelectronic system and were compared in 30 obese (OG; body mass index [BMI] = 39.6 +/- 0.6 kg.m(-2); 29.5 +/- 1.3 yr) and 19 normal body mass adults (NG; BMI 21.4 +/- 0.5 kg.m(-2); 31.2 +/- 1.2 yr) walking at PWS. Results: PWS was significantly lower in OG (1.18 +/- 0.02 m.s(-1)) than in NG (1.33 +/- 0.02 m.s(-1); P <= 0.001). There was no significant difference in W-ext per unit mass between groups (OG: 0.36 +/- 0.03 J.kg(-1).m(-1); NG: 0.31 +/- 0.02 J.kg(-1).m(-1); P = 0.12). R-step was significantly lower in OG (68.4% +/- 2.0%) compared with NG (74.4% +/- 1.0%; P = 0.01). In OG only, W-ext per unit mass was positively correlated with PWS (r = 0.57; P < 0.001). Conclusion: Obese adults do not appear to alter their gait to improve pendular energy transduction and may select slower PWS to reduce mechanical and metabolic work.