Measuring movement fluency during the sit-to-walk task

Background: Restoring movement fluency is a key focus for physical rehabilitation; it's measurement, however, lacks objectivity. The purpose of this study was to find whether measurable movement fluency variables differed between groups of adults with different movement abilities whilst performing the sit-to-walk (STW) movement. The movement fluency variables were: (1) hesitation during movement (reduction in forward velocity of the centre of mass; CoM), (2) coordination (percentage of temporal overlap of joint rotations) and (3) smoothness (number of inflections in the CoM jerk signal). Methods: Kinematic data previously collected for another study were extracted for three groups: older adults (n = 18), older adults at risk of falling (OARF, n = 18), and younger adults (n = 20). Each subject performed the STW movement freely while a motion analysis system tracked 11 body segments. The fluency variables were derived from the processed kinematic data and tested for group variation using analysis of variance. Findings: All three variables showed statistically significant differences among the groups. Hesitation (F = 15.11, p < 0.001) was greatest in the OARF 47.5% (SD 18.0), compared to older adults 30.3% (SD 15.9) and younger adults 20.8% (SD 11.4). Co-ordination (F = 44.88, p < 0.001) was lowest for the OARF (6.93%, SD 10.99) compared to both the young (31.21%, SD 5.48) and old (26.24%, SD 5.84). Smoothness (F = 35.96, p < 0.001) was best in the younger adults, 18.3 (SD 5.2) inflections, compared to the old, 42.5 (SD 11.5) and OARF, 44.25 (SD 7.29). Interpretation: Hesitation, co-ordination and smoothness may be valid indicators of movement fluency in adults, with important consequences for research and clinical practice. (C) 2012 Elsevier B.V. All rights reserved.