Effects of pace on stabilization after rising from a chair in young and older adults

Abstract

Falls are of significant concern for an aging population, and with 14% of falls thought to occur during the transition from sitting to standing this is a task that could be further assessed. Looking at a relatively new phase of the task, the stabilization phase could provide insight into movement and allow for better evaluation of those at risk. The purpose of the study was to determine the effect of chair rising speed on stabilization phase stability in young and older adults. Twenty healthy older adults (between the ages of 65-80 yrs) and 20 young adults (ages 18-33 yrs) performed the task of rising from a chair after a series of functional tests were performed. Four single repetitions of the task were performed at a comfortable pace (CSTS) along with four repetitions at a maximal fast pace (FSTS) in a randomized block design. Measurements of the ground reaction forces and moments were recorded during the task and for at least 15 seconds following completion so that the movement phase, length of the stabilization period and events within the stabilization phase could be examined. The older adults exhibited lower five time sit-to-stand, short physical performance battery (SPPB), grip strength, and Activities Specific Balance Confidence (ABC) survey scores compared with the young adults. The movement time (MT) decreased between the comfortable and fast condition. However, duration of the stabilization phase was significantly greater in the between pace conditions only in the anterior-posterior direction. The older adults did not produce significantly longer stabilization phase lengths compared to the young. The older adults did see significantly greater movement regarding the center of pressure (COP) movement within the first 2s of stabilization. The older adults also exhibited significantly greater trial-to-trial variability in the COP variables. The GRFv variables were correlated between the CSTS and FSTS amongst the older adults, but this was not the case for they young, nor for the COP variables in both groups. The event just prior to the stabilization phase the rising phase minimum (GRFv RPmin) had the greatest correlation with events in the first 2s of the stabilization for the older adults during the FSTS, although this relationship was not seen for the young adult or during CSTS in both groups. The older adults exhibited greater between trial variability further displaying the common effects of aging. The correlation between movement phase variables and events of the stabilization phase were greater in the older adults, with the events prior to reaching standing posture and within the first 2s of the stabilization phase revealing differences among age and condition. Considering the lack of correlations between the COP variables in the CSTS and the FSTS indicates that both conditions are unique and warrant further research. Performing the CSTS along does not tell the complete story relative to dynamic stability. It would appear that a short window of the stabilization phase may be more revealing than determining the duration of the stabilization phase. The functional differences displayed between our young and older adults and the differences noticed within the stabilization phase reveal that varying pace may be an appropriate means to assess function and could identify those at greater risk of falling.