Impact of excess body weight on walking at the preferred speed.

The implications of a long-lasting mechanical load on the locomotor activity are poorly understood. The objective of the present studies was to determine an impact of excess body weight on basic spatiotemporal gait measures and to test the hypothesis that leg swing phase may account for a load-related adaptation of the stride characteristics. To this end the basic spatial and temporal stride measures were assessed in 100 obese and 36 lean women (age range between 18 and 67 years) walking with their self-selected pace on a 10-meter long and 1 meter wide instrumented pathway. Among the subjects there were: 44 with class I obesity, 27 with class II obesity, and 29 with class III. Subjects' stance and swing times as well as the stride lengths were recorded by means of contact copper-film electrodes attached to a sole of subject' footwear. The acquired gait measures were used then to compute: a mean velocity of walking, double support times and a mean velocity of a foot during swing phase. Data analysis showed that subjects from every experimental groups walked with a very similar speed (1.08 +/- 0.2 m/s) and cadence (106 +/- 10 steps/min). Their stance time was not affected by body weight and it remained at the mean level of 746 +/- 90 ms for all groups. The temporal stride characteristics and the stance-to-swing ratio were, however, substantially modified in obese individuals due to attenuation of the swing time. As a consequence, the remaining normalized (i.e., expressed as percentage of gait cycle time) phases of stride: the stance and the double support were relatively longer. While the swing time negatively correlated with the body mass index (BMI), the normalized stance and the double support exhibited strong positive correlation (r=0.46) with the BMI. The increase of leg swing velocity seems the main and unique adaptation mechanism that is utilized in the preferred walking gait in obese women.