Gareth Jones – Abstract

P11  Estimates of gait initiation-onset in both stroke and healthy individuals during the sit-to-walk task

Jones GD[1, 2], James DC[3], Thacker M[1, 2, 4], Perry R[2], and Green DA[1, 5, 6]

  1. Centre for Human and Applied Physiological Sciences (CHAPS), Faculty of Life Sciences & Medicine, King’s College London, London, UK
  2. Department of Physiotherapy, Guy’s & St Thomas’ NHS Foundation Trust, London, UK
  3. Sport and Exercise Science Research Centre, London South Bank University, London, UK
  4. Allied Health Sciences, London South Bank University, London, UK.
  5. European Astronaut Centre, Directorate of Human Spaceflight and Robotic Exploration Programmes (D/HRE), European Space Agency, Cologne, Germany
  6. 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 [3]. However, it has poor utility following stroke, with alternative estimation methods typically deployed [4]. 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.

  1. Buckley, T., et al., Age impairs sit-to-walk motor performance. Journal of Biomechanics, 2009. 42(14): p. 2318-22.
  2. Magnan, A., B.J. McFadyen, and G. St-Vincent, Modification of the sit-to-stand task with the addition of gait initiation. Gait & Posture, 1996. 4(3): p. 232-241.
  3. Kerr, A., B. Durward, and K.M. Kerr, Defining phases for the sit-to-walk movement. Clinical Biomechanics, 2004. 19(4): p. 385-90.
  4. Frykberg, G.E., et al., Temporal coordination of the sit-to-walk task in subjects with stroke and in controls. Archives of Physical Medicine and Rehabilitation, 2009. 90(6): p. 1009-17.