Do mechanical gait parameters explain the higher metabolic cost of walking in obese adolescents?
Net metabolic cost of walking normalized by body mass (C(W.BM(-1)); in J.kg(-1).m(-1)) is greater in obese than in normal-weight individuals, and biomechanical differences could be responsible for this greater net metabolic cost. We hypothesized that, in obese individuals, greater mediolateral body center of mass (COM) displacement and lower recovery of mechanical energy could induce an increase in the external mechanical work required to lift and accelerate the COM and thus in net C(W.BM(-1)). Body composition and standing metabolic rate were measured in 23 obese and 10 normal-weight adolescents. Metabolic and mechanical energy costs were assessed while walking along an outdoor track at four speeds (0.75-1.50 m/s). Three-dimensional COM accelerations were measured by means of a tri-axial accelerometer and gyroscope and integrated twice to obtain COM velocities, displacements, and fluctuations in potential and kinetic energies. Last, external mechanical work (J.kg(-1).m(-1)), mediolateral COM displacement, and the mechanical energy recovery of the inverted pendulum were calculated. Net C(W.BM(-1)) was 25% higher in obese than in normal-weight subjects on average across speeds, and net C(W.BM(-67)) (J.kg(-0.67).m(-1)) was significantly related to percent body fat (r(2) = 0.46). However, recovery of mechanical energy and the external work performed (J.kg(-1).m(-1)) were similar in the two groups. The mediolateral displacement was greater in obese subjects and significantly related to percent body fat (r(2) = 0.64). The mediolateral COM displacement, likely due to greater step width, was significantly related to net C(W.BM(-67)) (r(2) = 0.49). In conclusion, we speculate that the greater net C(W.BM(-67)) in obese subjects may be partially explained by the greater step-to-step transition costs associated with wide gait during walking.
Peyrot
Nicolas
N
Laboratoire de Physiologie de l'Exercice, Médecine du Sport-Myologie, CHU Bellevue, 42055 Saint-Etienne Cedex 02, France. nicolas.peyrot@univ-st-etienne.fr
Thivel
David
D
Isacco
Laurie
L
Morin
Jean-Benoît
JB
Duche
Pascale
P
Belli
Alain
A
D000293:Adolescent; D001823:Body Composition; D015992:Body Mass Index; D001835:Body Weight; D002648:Child; D004734:Energy Metabolism / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D005684:Gait / Q000502:physiology*; D006801:Humans; D008297:Male; D009765:Obesity / Q000378:metabolism* / Q000503:physiopathology; D016138:Walking / Q000502:physiology*