Meeting Abstract

P1.163  Monday, Jan. 4  Effect of Age, Walking Speed, and Frontal Load on Step Width and its Variability MYERS, Marcella J*; BOEFF, Kelsey A; WALL-SCHEFFLER, Cara M; St Catherine University; St Catherine University; Seattle Pacific University mjmyers@stkate.edu

Step width (StW) has been proposed as a determinant of the cost of walking via affects on step-to-step transitions involved in redirecting the center of mass. Increased StW variability has been linked to frailty and/or fear of falling in older people, while increases in mean StW potentially compensate for lateral instability. The passive dynamic (PD) model of walking predicts that walkers are more stable in the fore-aft direction due to passive stability but less stable laterally, requiring active control of foot placement – an activity that might become less precise as sensory and motor systems age. A simple prediction of the PD model is that older walkers should have wider StW and greater StW variability than young walkers. We tested this prediction in a sample of 10 young (Y) females (mean=20.9, range 19-23 yr) and 10 older (O) females (mean=51.4, range 40-64 yr) as they walked on a treadmill unloaded and front-loaded (16% of body mass, such as experienced during pregnancy or post-menopausal shifts in visceral abdominal fat) at four speeds centered around optimal walking speeds. Although dividing StW by limb length (LL) is a common normalization technique, we found sharply different patterns between StW and LL in the two age cohorts (Y: StW vs LL virtually flat, O: StW increased directly and significantly with LL, r = 0.64, p < 0.0001). With speed and load in the model, StW was wider in the older group, but StW variability was less. We found that older walkers could be even more precise in their foot placement than younger walkers, although they did compensate with wider steps. Supported by NIH EARDA Grant G11HD039786 and the Center of Excellence for Women, Science & Technology at SCU.