[home] [Personal Program] [Help]

---

Session: Poster session I
Session starts: Thursday 24 January, 15:00

---

Luis Eduardo Cofré (Research Institute MOVE, Faculty of Human Movement Sciences, VU University)
Mirjam Pijnappels (Research Institute MOVE, Faculty of Human Movement Sciences, VU University)
Jaap van Dieën (Research Institute MOVE, Faculty of Human Movement Sciences, VU University)

Abstract:
It is thought that mediolateral balance control impairment may affect performance of important daily life activities such as walking, especially in the elderly [1, 2]. It has also been proposed that balance training in the frontal plane may reduce the incidence of falls in the elderly population [3]. Quantification and training of ones capacity to dynamically control mediolateral balance might therefore be a powerful tool in fall prevention. For this purpose, a zero order visual tracking task (VTT), using the centre of pressure (CoP), which demands the integration of multiple sensory inputs, is proposed. Balance performance during either a predictable or a pseudorandom VTT can be described in the frequency domain in terms of phase shift, and gain. The aim of this study was to determine whether learning effects occur in these tasks. . For this experiment, 20 healthy young subjects (28±3 yrs) stood barefoot on a force plate (Kistler) and performed a series of 4 VTTs with a predictable target and 4 with a pseudorandom target, preceded by 2 practice trials for each task. The VTT consisted of tracking a target signal on a screen in front of the subject, by a projection of the ML displacement of the CoP. The frequency of the target increased from 0.3 to 2.0 Hz. For the predictable target, the frequency increased with steps of 0.1 Hz every 5 seconds. For the pseudorandom target, multisines with a bandwidth of 0.6 Hz and lowest frequency increasing from 0.3 to 1.5 Hz at 0.1 Hz were used. D-Flow (Motek Medical, The Netherlands) was used to produce target signals and project CoP feedback (spheroids). Performance was expressed as the gain and phase-shift between the target and CoP projection. Repeated measures ANOVAs were performed to assess learning effects at frequencies from 0.3 To 2.0 Hz, with an alpha of 0.01. For the predictable task, significant learning effects were found at 1.5 and 1.7 Hz in phase shift, and at 0.3-0.4 and 1.1-1.2 Hz in gain (all p<0.01). For the pseudorandom target, significant learning effects were observed for phase shift at all frequencies analyzed (p<0.01), except at 0.3 and 0.4 Hz, while gain exhibited a significant learning effect only at 0.4 and 0.5 Hz. Overall, close to optimal values and no major learning effects were found over the range of frequencies for the predictable task, indicating that physical constraints do not limit performance in CoP tracking up to 2 Hz. When comparing both tasks, larger phase shifts and lower gains in pseudorandom tracking indicate that information processing may be a limiting factor. For the pseudorandom task, the phase-shift decreased substantially over sessions. This may indicate the information processing required in the pseudorandom task can be improved with a single session and the effect can be maintained up to one week REFERENCES 1. O'Connor, S.M. and A.D. Kuo, Direction-Dependent Control of Balance During Walking and Standing. Journal of Neurophysiology, 2009. 102(3): p. 1411-1419. 2. Maki, B.E., P.J. Holliday, and A.K. Topper, A prospective-study of postural balance and risk of falling in an ambulatory and independent elderly population. Journals of Gerontology, 1994. 49(2): p. M72-M84. 3. Waddell, C.L., R.B. Mellifont, and B.J. Burkett, Improving balance in community-dwelling older people through a targeted mediolateral postural stability program. Journal of the American Geriatrics Society, 2009. 57(12): p. 2380-2382.