P11 Estimates of gait initiation-onset in both stroke and healthy individuals during the sit-to-walk task
Jones GD[1, 2], James DC, Thacker M[1, 2, 4], Perry R, and Green DA[1, 5, 6]
- Centre for Human and Applied Physiological Sciences (CHAPS), Faculty of Life Sciences & Medicine, King’s College London, London, UK
- Department of Physiotherapy, Guy’s & St Thomas’ NHS Foundation Trust, London, UK
- Sport and Exercise Science Research Centre, London South Bank University, London, UK
- Allied Health Sciences, London South Bank University, London, UK.
- European Astronaut Centre, Directorate of Human Spaceflight and Robotic Exploration Programmes (D/HRE), European Space Agency, Cologne, Germany
- KBRwyle GmbH, Albin Köbis Straße 4, Cologne, 51147, Germany
Gait-initiation (GI) during sit-to-walk (STW) includes an anticipatory-phase where the centre-of-pressure moves towards the swing-limb before an execution-phase begins with heel-off, similar to GI from quiet-standing [1,2]. The mediolateral ground-reaction-force (xGRF) breaching a pre-determined threshold from sit-to-stand (STS) trials normally estimates STW GI-onset . However, it has poor utility following stroke, with alternative estimation methods typically deployed . We aimed to determine the extent of xGRF-threshold failure in stroke, and test the hypothesis that alternatives estimate GI-onset later during anticipatory or execution-phases of GI.
Twenty (7F) stroke individuals [median(IQR) age=60(50-64years)], and twenty-one (7F) age-matched healthy volunteers [64(51-75years)] performed 5 standardised STW and STS trials. Force-plates and optical motion determined 4 GI-onset estimations; xGRF threshold (xGRFthresh), maximum xGRF (xGRFmax), maximum swing-limb vertical GRF (vGRFmaxSWING), and heel-off (firstHEELoff). Differences in transition-times (seat-off–GI-onset) across methods were assessed using Kruskal-Wallis tests.
In stroke, there was no statistical difference in transition-time across methods with median vGRFmaxSWING the shortest estimate [0.522(0.303-1.435s)]. Healthy individuals’ transition-times differed across methods [2(3)=29.264; p<0.001]. Median xGRFmax transition-time [0.183(0.083-0.270s)] and vGRFmaxSWING [0.080(0.020-0.180s)] consistently placed GI-onset within the GI anticipation-phase, albeit later than xGRFthresh [0.027(-0.033-0.098s)], with firstHEELoff placing it later in the execution-phase [0.293(0.167-0.365s)]. In 49% of stroke, and 6% of healthy trials, equivalent peak xGRFs during STW and STS meant GI-onset using xGRFthresh was indeterminate because xGRF failed to breach the pre-determined threshold.
Estimating GI-onset using xGRFthresh is not appropriate in individuals with stroke. In contrast, maxSUMxGRF or maxSWINGvGRF are practical methods to estimate anticipatory-phase GI-onset regardless of STW performance dynamics.
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