Effect of Arm Motion on Postural Strategies During Uphill and Downhill Walking

The aim of this study was to investigate the effects of arm motion and surface slope on postural strategies and gait stability. We hypothesized that active arm swing would increase postural control compared to walking with arms held and normal arm swing, and that holding the arms would lead to an increasing number of compensatory gait strategies with the aim of increasing balance, both uphill and downhill. We tested fifteen healthy, young adults (age 23.4 ± 2.8 years) using the Computer-Assisted Rehabilitation ENvironment (CAREN) using a simulated rolling-hills condition under 3 arm swing conditions: held, normal, and active. Outcome measures included spatiotemporal gait parameters and postural stability measures in the 3 planes of motion (anterior-posterior, medial-lateral, and vertical). No significant interaction effects between arm swing and surface slope were found. However, results showed main effect for arms (held, normal, active) and slope (uphill versus level walking, downhill versus level walking) conditions. Stepping and postural strategies when walking uphill compared to level were opposite to those used in downhill walking compared to level. Participants adopted an overall more cautious strategy when walking downhill, as seen by a combination of decreased cadence and increased double-support time, while the opposite strategies were seen in uphill walking. Effects of arm swing remained relatively consistent for both uphill and downhill walking conditions. Both uphill and downhill, holding the arms led to stability-seeking measures in the form of increasing base of support (double-support time), and increased control (decreased vertical accelerations of the head and trunk compared to normal and active arm swing). These results substantiate the destabilizing effects of walking without arm swing and the usefulness of active arm swing for enhancing gait stability on minor slopes. This research also provides insight into the control mechanisms regulating dynamic balance in healthy young adults, which can be used to inform protocols and develop models aimed at preventing occupational health and safety hazards in challenging environments (e.g. construction workers). Abstract The aim of this study was to investigate the combined effects of arm motion and surface slope on postural strategies and gait stability in a healthy population. The Computer-Assisted Rehabilitation ENvironment was used to test participants (n = 15) in a simulated rolling-hills environment which imparted both incline and decline conditions (-3 to +3º). The protocol was completed under three arm swing conditions: held, normal, and active. Outcome measures included spatiotemporal gait parameters and postural control measures in the anterior-posterior (AP), medial-lateral (ML), and vertical (VT) directions. Gait parameters included step time, step width, cadence, single-support time, and double-support time, as well as coefficient of variation for step time, step width, and double-support time; Postural measures included mean postural alignment (position of C7 relative to pelvis), mean center of mass position, head acceleration, and trunk acceleration. No significant interaction effects between arm swing and surface slope were found. However, results showed main effect for arms and for slope (uphill versus level and downhill versus level). Stepping and postural strategies when walking uphill compared to level were opposite to those used in downhill walking compared to level. Participants adopted an overall more cautious strategy when walking downhill, as seen by a combination of decreased cadence and increased double-support time, while the opposite strategies were seen in uphill walking. As for the effect of arm motion, walking with arms held resulted in participants increasing double-support time and increasing control of the head and trunk in VT compared to normal and active arm swing. Conversely, active arm swing decreased double-support time and caused a forward shift in postural alignment. These results substantiate the destabilizing effects of walking without arm swing and the usefulness of active arm swing for enhancing gait stability on minor slopes. No found ML for postural alignment (2,15) p2 . 001, p , CoM (F (2,15) p head acceleration (F (2,15) = η p2 = . 051, p = or trunk acceleration (F p sloped with gait impairments strategies used control” active arm swing