Effects of Obesity on the Biomechanics of Walking at Different Speeds.
Medicine & Science in Sports & Exercise. 39(9):1632-1641, September 2007.
BROWNING, RAYMOND C.; KRAM, RODGER
Purpose: Walking is a recommended form of exercise for the treatment of obesity, but walking may be a critical source of biomechanical loads that link obesity and musculoskeletal pathology, particularly knee osteoarthritis. We hypothesized that compared with normal-weight adults 1) obese adults would have greater absolute ground-reaction forces (GRF) during walking, but their GRF would be reduced at slower walking speeds; and 2) obese adults would have greater sagittal-plane absolute leg-joint moments at a given walking speed, but these moments would be reduced at slower walking speeds.
Methods: We measured GRF and recorded sagittal-plane kinematics of 20 adults (10 obese and 10 normal weight) as they walked on a level, force-measuring treadmill at six speeds (0.5-1.75 m[middle dot]s-1). We calculated sagittal-plane net muscle moments at the hip, knee, and ankle.
Results: Compared with their normal-weight peers, obese adults had much greater absolute GRF (N), stance-phase sagittal-plane net muscle moments (N[middle dot]m) and step width (m).
Conclusions: Greater sagittal-plane knee moments in the obese subjects suggest that they walked with greater knee-joint loads than normal-weight adults. Walking slower reduced GRF and net muscle moments and may be a risk-lowering strategy for obese adults who wish to walk for exercise. When obese subjects walked at 1.0 versus 1.5 m[middle dot]s-1, peak sagittal-plane knee moments were 45% less. Obese subjects walking at approximately 1.1 m[middle dot]s-1 would have the same absolute peak sagittal-plane knee net muscle moment as normal-weight subjects when they walk at their typical preferred speed of 1.4 m[middle dot]s-1.