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


Medicine & Science in Sports & Exercise: February 2009 - Volume 41 - Issue 2 - p 426-434
doi: 10.1249/MSS.0b013e31818606e7
Applied Sciences

Purpose: The aim of this study was to compare the mechanical external work (per kg) 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 (Wext) and the fraction of mechanical energy recovered by the pendular mechanism (Rstep) 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 Wext 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). Rstep was significantly lower in OG (68.4% ± 2.0%) compared with NG (74.4% ± 1.0%; P = 0.01). In OG only, Wext 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.

1Institute of Sport Sciences and Physical Education (ISSEP), University of Lausanne, Lausanne, SWITZERLAND; 2Orthopaedic Rehabilitation Unit and Clinical Lab for Gait and Posture Analysis, San Giuseppe Hospital, Istituto Auxologico Italiano, IRCCS, Piancavallo (VB), ITALY; and 3Bioengineering Department, Politecnico di Milano, ITALY

Address for correspondence: Davide Malatesta, Ph.D., Institute of Sport Sciences and Physical Education (ISSEP), University of Lausanne, Bâtiment Vidy, Bureau no.107, 1015, Lausanne, SWITZERLAND; E-mail:

Submitted for publication December 2007.

Accepted for publication July 2008.

©2009The American College of Sports Medicine