Decreased Trunk Angular Displacement During Sitting Down: An Early Feature of Aging

Background and Purpose. Trunk motion plays an important role in achieving both sit-to-stand and stand-to-sit transfers. However, these 2 body transfers depend on different postural and mechanical constraints. Although the effects of aging on sit-to-stand transfers have been widely studied, there is a lack of information concerning stand-to-sit transfers. The aim of this study was to determine how angular displacements of the trunk and shank are affected by aging during sit-to-stand and stand-to-sit transfers. Subjects. Ten community-dwelling older adults (mean age=75.9 years, SD=3.2) and 9 young adults (mean age=26.8 years, SD=4.7) volunteered to participate. Methods. Maximal angular displacements of the trunk and shank with respect to the vertical (ie, orientation angles) were measured, during standing up and sitting down, using an optoelectronic movement analyzer. Results. For standing up, there was no difference between the young and older adults with regard to both maximal orientation angles. During sitting down, the maximal shank orientation angle was not affected by age, whereas the older adults had a smaller trunk motion compared with the young adults (approximately 10° less). Discussion and Conclusion. The results showed that older adults tended to minimize the forward body displacement during sitting down. This strategy could be seen as an adaptive mechanism to decrease the risk of anterior disequilibrium. The authors suggest that this feature could be used as an early marker of aging on postural control.