Table 3 |
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Balance tests performed before and after training |
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Task conditions |
Response observed |
Perturbations and numbers of trials† |
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Familiarisation: Stance, unconstrained arm and foot motion (instructed to react naturally) |
not applicable |
4 medium translations‡ (F,B,L,R) 4 large translations‡ (F,B,L,R) 4 waist pulls (F,B,L,R) Total = 12 trials |
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Trial block #1: Stance, arm motion restricted, instructed to react naturally but minimise number of steps |
Compensatory stepping main focus: multiple-step responses (a-p perturbations) |
5 backward translations 3 forward translations 2 lateral translations (L,R)§ 4 translations, 2nd waveform (F,B,L,R)# 5 forward waist pulls 3 backward waist pulls 2 lateral waist pulls (L,R)§ Total = 24 trials |
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Trial block #2: Walking in-place, arm motion restricted, instructed to react naturally but minimise number of steps |
Compensatory stepping main focus: foot collisions (lateral perturbations) |
5 leftward translations 3 rightward translations 2 a-p translations (F,B)§ 4 translations, 2nd waveform (F,B,L,R)# 5 rightward waist pulls 3 leftward waist pulls 2 a-p waist pulls (F,B)§ Total = 24 trials |
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Trial block #3: Stance, foot motion restricted, instructed to recover balance by grasping handrail (at right of subject) |
Compensatory grasping main focus: speed of grasping (a-p perturbations) |
5 forward translations 4 backward translations§ 4 forward waist pulls§ 5 backward waist pulls Total = 18 trials |
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†During trial blocks #1–3, the listed platform-translation and waist-pull perturbations are delivered in an unpredictable randomised sequence, in the directions indicated (F = forward, B = backward, L = left, R = right; a-p = antero-posterior) ‡ The familiarisation block includes initial medium-magnitude platform perturbations, followed by the same large-magnitude perturbations that are used in the main trial blocks. The platform acceleration of the large perturbations (2.0 m/s2 forward, 3.0 m/s2 other directions) is 50% greater than the medium perturbations (1.3 m/s2 forward, 2.0 m/s2 other directions). § These tests are included primarily for the purpose of increasing the unpredictability of the perturbation direction and will not be part of the main analysis # The 2nd waveform tests will not be part of the main analysis, but are included to deter subjects from learning to use the deceleration of the platform to aid in recovering balance [46]. The usual waveform comprises a 300 ms acceleration pulse followed immediately by a 300 ms deceleration pulse. The 2nd waveform comprises a 200 ms acceleration pulse and a 400 ms constant-velocity interval, prior to a 200 ms deceleration pulse. The acceleration magnitude for this second waveform ranges from 1.35 m/s2 to 2.25 m/s2. |
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Mansfield et al. BMC Geriatrics 2007 7:12 doi:10.1186/1471-2318-7-12 |
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