Article

One-leg stance in healthy young and elderly adults: a measure of postural steadiness?

Karolinska Institutet, Neurotec Department, Division of Physiotherapy, Motor Control and Physical Therapy Research Laboratory, 23100, 141 83 Huddinge, Sweden.
Clinical Biomechanics (Impact Factor: 1.88). 09/2004; 19(7):688-94. DOI: 10.1016/j.clinbiomech.2004.04.002
Source: PubMed

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.

3 Followers
 · 
190 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Control of standing requires the continuous activity of the leg muscles. In single leg standing the system is less redundant and muscular activity is more intensive. The objective of this study was to examine the effect of force imbalance of the shank muscles, evoked by their selective fatiguing, on postural control in single-leg standing. Five healthy subjects performed two single-leg standing trials, lasting as long as the subject could maintain steady balance, and separated by a 240s quasi-isotonic sustained effort to induce fatigue of the Tibialis Anterior and Peroneus muscles. The following were on-line monitored: sway-related parameters, e.g., ground reaction force and center of pressure in the standing trials; and electromyogram of the Tibialis Anterior, Peroneus and Gastrocnemius muscles in all experiments. Simple and multiple linear regressions served to study the fatigue effects on the relationship between muscle activity and postural sway. The results indicate that the evoked muscle imbalance leads to (a) increased postural sway; (b) increased correlation between muscle activity, and sway-related parameters. Thus, with the reduction of the level of redundancy the system becomes more synchronized. These results have potential relevance for cases of muscle impairment, in which electrical stimulation is required to augment muscle activity.
    Journal of Electromyography and Kinesiology 09/2008; 18(4):682-9. DOI:10.1016/j.jelekin.2007.01.009 · 1.73 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Functional ankle instability is defined as the subjective sensation of giving way or feeling joint instability after repeated episodes of ankle sprain. The purpose of this study was to examine the effects of 12-week biomechanical ankle platform system training on static postural stability and ankle reposition sense in subjects with unilateral functional ankle instability. Twelve university students (4 females and 8 males) with unilateral functional ankle instability volunteered as subjects. The active and passive reposition senses were assessed using an isokinetic dynamometer. The mean radius of the center of pressure excursion was recorded during single-leg standing with a force platform. A 12-week training program and a progression test for controlling the platform in certain directions and advancing to next training level was given to each subject. Repeated-measures 2-way analyses of variance were conducted to determine differences in postural stability and ankle proprioception between each limb before and after the training period. The mean radius of center of pressure on unilateral standing and the absolute error from pre-selected ankle angle in the functional ankle instability limb were significantly reduced after 12 weeks of training. These improvements in postural stability appear to reflect improved neuromuscular ability along with enhanced functional joint stability, as ankle proprioception also demonstrated the same positive improvements after training.
    Clinical Biomechanics 08/2008; 23(8):1065-72. DOI:10.1016/j.clinbiomech.2008.04.013 · 1.88 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    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