The role of arm movement in early trip recovery in younger and older adults.

The aims of this study were to investigate which arm movements are made during trip recovery, to determine the contributions of arm movements in trip recovery and to identify differences in these contributions between younger and older adults and different recovery strategies. A group of seven older adults (65-75 years) and a group of eight younger adults (20-35 years) were examined. Participants completed a trip recovery protocol in which 3-D kinematic and kinetic data were collected for recovery movements following unexpected trips during locomotion. In younger adults, arm movements were associated with an elevated body centre of mass (CM) position during recovery. Arm movements also served to reduce the angular momentum in the direction of the trip by 13% between trip stimulus and recovery foot contact in 'elevating' recovery strategies. Arm movements in older adults contributed an additional 3% to the destabilising angular momentum during 'elevating' recoveries. It was concluded that older adults exhibit a more 'protective' recovery strategy (to limit injury resulting from fall impacts following loss of balance) and younger adults exhibit a more 'preventive' strategy (to prevent loss of balance).