Increased risk for falling associated with obesity: mathematical modeling of postural control

TLDR

Obesity is linked to higher fracture incidence. The study uses a postural control model to examine how abdominal fat distribution affects postural stability. The model destabilized humanoids with a small angular speed and simulated ankle torque parameters to detect loss of stability when the center of pressure exceeded stability margins. The model shows that delayed ankle torque and anterior center of mass markedly increase the torque required for stability, indicating that obese individuals with abdominal fat are at higher fall risk.

Abstract

Recent epidemiological studies report that obesity is positively related to fracture incidence. In the present experiment, a model of postural control was used to examine the impact of an abnormal distribution of body fat in the abdominal area upon postural stability. Obese and lightweight humanoids were destabilized by imposing a small initial angular speed from a neutral standing position. To avoid a loss of stability yielding a stepping reaction or a fall, an ankle torque is necessary to counteract the perturbation. Three torque parameters-ankle torque onset, time to peak torque, and muscular ankle torque-were entered in a program to simulate the intrinsic variability of the human postural control system. A loss of stability was detected when the center of pressure exceeded stability margins. The most striking observation is the nonlinear increase of torque needed to stabilize the humanoid when the motor response was chararterized by delayed temporal parameters. The effect was more pronounced when an anterior position of the center of mass was included in the simulations. This suggests that, when submitted to daily postural stresses and perturbations, obese persons (particularly those with an abnormal distribution of body fat in the abdominal area) may be at higher risk of falling than lightweight individuals.