Obesity-related alterations in anticipatory postural mechanisms associated with gait initiation.

Obesity is known to have a detrimental effect on balance and motor performance during daily motor tasks. However, it remains unclear whether these obesity-related impairments are due to deficient anticipatory postural adjustments (APA) that precede voluntary movement. The objective of this study was to examine the effects of obesity on APA and the impacts related on motor performance and mediolateral postural stability during gait initiation. Fifteen obese and ten normal-weight young participants performed a series of gait initiation at their preferred speed. Our results showed that the durations and amplitudes of APA along both anteroposterior and mediolateral directions did not differ between the two groups (P > 0.05). In contrast, compared to normal-weight participants, mechanical effectiveness of APA was reduced in obese participants (P < 0.05). As a result, we observed a decreased motor performance (P < 0.05), in terms of peak anteroposterior center-of-mass velocity at the end of the first step, and a reduced mediolateral stability at swing foot contact in obese participants compared to normal-weight participants (P < 0.05). These findings suggest that APA effectiveness during gait initiation is reduced in obese adults, resulting in a decrease of both mediolateral stability and motor performance compared to their lean counterparts.