One-leg stance in healthy young and elderly adults: a measure of postural steadiness?
ABSTRACT To investigate postural steadiness during 30 s of one-leg stance in healthy young and elderly adults, by analysing the pattern of the ground reaction force variability.
A laboratory set-up was used to analyse the variability of the ground reaction forces in relation to time as a measure of postural steadiness.
The one-leg stance test is a measure considered to assess postural steadiness in a static position by a temporal measurement. The common notion is that a better postural steadiness, i.e. less force variability, allows for longer time standing on one leg. However, there is lack of evidence how postural steadiness during one-leg stance changes over time.
Twenty-eight healthy elderly and 28 healthy young adults were tested by means of force plates assessing ground reaction forces while performing one-leg stance.
During one-leg stance, two phases could be identified in both groups: First a dynamic phase, a rapid decrease of force variability, and thereafter a static phase, maintaining a certain level of force variability. During the first 5 s of one-leg stance the force variability decreased significantly more in the young group resulting in a lower force variability level during the static phase than in the elderly.
The difficulties in maintaining the static position in elderly seems dependent on the reduced initial decrease in force variability and/or musculoskeletal components. We suggest that the first 5 s are crucial when assessing balance during one-leg stance.
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ABSTRACT: Motion measurement is a key function for patient diagnosis, therapy and rehabilitation in clinical disciplines ranging physiology, audiology, orthopaedics, neurophysiology. The equipment can be by video camera recording, machine vision systems and force plates. Motion analysis systems supported by multi-camera machine vision systems are an expensive solution for many applications. Force plates are another measurement tool that can be used in conjunction with a machine vision system or as a separate system. In the case of the latter set-up, the force plate is able to measure the centroid and vector of the ground reaction force, and the data retrieved can be interpreted by clinical staff to determine the nature of balance or stance of a patient. There is valuable information in the transients that can be detected by this approach, however the force plate cannot be utilised to discriminate other spatial factors in the way that the loads are applied by the patient on the surface. This paper reports the distributive approach to tactile sensing applied to infer the 3 dimensional motion of a moving mass in a supporting mechanism placed on the 2 dimensional sensing surface. The distributive approach has the advantage over forceplates on constructional costs and the ability to discriminate many motion metrics of patients. Implementation of the system using only three low cost deflection sensing elements, positioned under the surface with the resulting signals interpreted by neural network implemented on a field programmable gate array (FPGA) output near real time sampling rates greater than 70 KHz. The investigation demonstrates that the performance is sufficiently accurate for the intended clinical application, having backing errors of less than 5% in all three dimensions.Mechatronics and Machine Vision in Practice, 2007. M2VIP 2007. 14th International Conference on; 01/2008