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Quiet Standing (quiet + standing)
Selected AbstractsMechanisms of Postural Control in Alcoholic Men and Women: Biomechanical Analysis of Musculoskeletal Coordination During Quiet StandingALCOHOLISM, Issue 3 2010Edith V. Sullivan Background:, Excessive sway during quiet standing is a common sequela of chronic alcoholism even with prolonged sobriety. Whether alcoholic men and women who have remained abstinent from alcohol for weeks to months differ from each other in the degree of residual postural instability and biomechanical control mechanisms has not been directly tested. Method:, We used a force platform to characterize center-of-pressure biomechanical features of postural sway, with and without stabilizing conditions from touch, vision, and stance, in 34 alcoholic men, 15 alcoholic women, 22 control men, and 29 control women. Groups were matched in age (49.4 years), general intelligence, socioeconomic status, and handedness. Each alcoholic group was sober for an average of 75 days. Results:, Analysis of postural sway when using all 3 stabilizing conditions versus none revealed diagnosis and sex differences in ability to balance. Alcoholics had significantly longer sway paths, especially in the anterior,posterior direction, than controls when maintaining erect posture without balance aids. With stabilizing conditions the sway paths of all groups shortened significantly, especially those of alcoholic men, who demonstrated a 3.1-fold improvement in sway path difference between the easiest and most challenging conditions; the remaining 3 groups, each showed a ,2.4-fold improvement. Application of a mechanical model to partition sway paths into open-loop and closed-loop postural control systems revealed that the sway paths of the alcoholic men but not alcoholic women were characterized by greater short-term (open-loop) diffusion coefficients without aids, often associated with muscle stiffening response. With stabilizing factors, all 4 groups showed similar long-term (closed loop) postural control. Correlations between cognitive abilities and closed-loop sway indices were more robust in alcoholic men than alcoholic women. Conclusions:, Reduction in sway and closed-loop activity during quiet standing with stabilizing factors shows some differential expression in men and women with histories of alcohol dependence. Nonetheless, enduring deficits in postural instability of both alcoholic men and alcoholic women suggest persisting liability for falling. [source] Control of the triceps surae during the postural sway of quiet standingACTA PHYSIOLOGICA, Issue 3 2007C. D. Tokuno Abstract Aim:, The present study investigated how the triceps surae are controlled at the spinal level during the naturally occurring postural sway of quiet standing. Methods:, Subjects stood on a force platform as electrical stimuli were applied to the posterior tibial nerve when the center of pressure (COP) was either 1.6 standard deviations anterior (COPant) or posterior (COPpost) to the mean baseline COP signal. Peak-to-peak amplitudes of the H-reflex and M-wave from the soleus (SOL) and medial gastrocnemius (MG) muscles were recorded to assess the efficacy of the Ia pathway. Results:, A significant increase in the Hmax : Mmax ratio for both the SOL (12 ± 6%) and MG (23 ± 6%) was observed during the COPant as compared to the COPpost condition. The source of the modulation between COP conditions cannot be determined from this study. However, the observed changes in the synaptic efficacy of the Ia pathway are unlikely to be simply a result of an altered level of background electromyographic activity in the triceps surae. This was indicated by the lack of differences observed in the Hmax : Mmax ratio when subjects stood without postural sway (via the use of a tilt table) at two levels of background activity. Conclusions:, It is suggested that the phase-dependent modulation of the triceps surae H-reflexes during the postural sway of quiet standing functions to maintain upright stance and may explain the results from previous studies, which, until now, had not taken the influence of postural sway on the H-reflex into consideration. [source] Prevention of Postmenopausal Bone Loss by a Low-Magnitude, High-Frequency Mechanical Stimuli: A Clinical Trial Assessing Compliance, Efficacy, and Safety,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 3 2004Clinton Rubin Abstract A 1-year prospective, randomized, double-blind, and placebo-controlled trial of 70 postmenopausal women demonstrated that brief periods (<20 minutes) of a low-level (0.2g, 30 Hz) vibration applied during quiet standing can effectively inhibit bone loss in the spine and femur, with efficacy increasing significantly with greater compliance, particularly in those subjects with lower body mass. Introduction: Indicative of the anabolic potential of mechanical stimuli, animal models have demonstrated that short periods (<30 minutes) of low-magnitude vibration (<0.3g), applied at a relatively high frequency (20,90 Hz), will increase the number and width of trabeculae, as well as enhance stiffness and strength of cancellous bone. Here, a 1-year prospective, randomized, double-blind, and placebo-controlled clinical trial in 70 women, 3,8 years past the menopause, examined the ability of such high-frequency, low-magnitude mechanical signals to inhibit bone loss in the human. Materials and Methods: Each day, one-half of the subjects were exposed to short-duration (two 10-minute treatments/day), low-magnitude (2.0 m/s2 peak to peak), 30-Hz vertical accelerations (vibration), whereas the other half stood for the same duration on placebo devices. DXA was used to measure BMD at the spine, hip, and distal radius at baseline, and 3, 6, and 12 months. Fifty-six women completed the 1-year treatment. Results and Conclusions: The detection threshold of the study design failed to show any changes in bone density using an intention-to-treat analysis for either the placebo or treatment group. Regression analysis on the a priori study group demonstrated a significant effect of compliance on efficacy of the intervention, particularly at the lumbar spine (p = 0.004). Posthoc testing was used to assist in identifying various subgroups that may have benefited from this treatment modality. Evaluating those in the highest quartile of compliance (86% compliant), placebo subjects lost 2.13% in the femoral neck over 1 year, whereas treatment was associated with a gain of 0.04%, reflecting a 2.17% relative benefit of treatment (p = 0.06). In the spine, the 1.6% decrease observed over 1 year in the placebo group was reduced to a 0.10% loss in the active group, indicating a 1.5% relative benefit of treatment (p = 0.09). Considering the interdependence of weight, the spine of lighter women (<65 kg), who were in the highest quartile of compliance, exhibited a relative benefit of active treatment of 3.35% greater BMD over 1 year (p = 0.009); for the mean compliance group, a 2.73% relative benefit in BMD was found (p = 0.02). These preliminary results indicate the potential for a noninvasive, mechanically mediated intervention for osteoporosis. This non-pharmacologic approach represents a physiologically based means of inhibiting the decline in BMD that follows menopause, perhaps most effectively in the spine of lighter women who are in the greatest need of intervention. [source] Mechanisms of Postural Control in Alcoholic Men and Women: Biomechanical Analysis of Musculoskeletal Coordination During Quiet StandingALCOHOLISM, Issue 3 2010Edith V. Sullivan Background:, Excessive sway during quiet standing is a common sequela of chronic alcoholism even with prolonged sobriety. Whether alcoholic men and women who have remained abstinent from alcohol for weeks to months differ from each other in the degree of residual postural instability and biomechanical control mechanisms has not been directly tested. Method:, We used a force platform to characterize center-of-pressure biomechanical features of postural sway, with and without stabilizing conditions from touch, vision, and stance, in 34 alcoholic men, 15 alcoholic women, 22 control men, and 29 control women. Groups were matched in age (49.4 years), general intelligence, socioeconomic status, and handedness. Each alcoholic group was sober for an average of 75 days. Results:, Analysis of postural sway when using all 3 stabilizing conditions versus none revealed diagnosis and sex differences in ability to balance. Alcoholics had significantly longer sway paths, especially in the anterior,posterior direction, than controls when maintaining erect posture without balance aids. With stabilizing conditions the sway paths of all groups shortened significantly, especially those of alcoholic men, who demonstrated a 3.1-fold improvement in sway path difference between the easiest and most challenging conditions; the remaining 3 groups, each showed a ,2.4-fold improvement. Application of a mechanical model to partition sway paths into open-loop and closed-loop postural control systems revealed that the sway paths of the alcoholic men but not alcoholic women were characterized by greater short-term (open-loop) diffusion coefficients without aids, often associated with muscle stiffening response. With stabilizing factors, all 4 groups showed similar long-term (closed loop) postural control. Correlations between cognitive abilities and closed-loop sway indices were more robust in alcoholic men than alcoholic women. Conclusions:, Reduction in sway and closed-loop activity during quiet standing with stabilizing factors shows some differential expression in men and women with histories of alcohol dependence. Nonetheless, enduring deficits in postural instability of both alcoholic men and alcoholic women suggest persisting liability for falling. [source] Posturographic analysis of balance control in patients with essential tremorMOVEMENT DISORDERS, Issue 2 2006Marco Bove PhD Abstract Essential tremor (ET) is a common movement disorder causing an important functional disability. ET is generally regarded as a monosymptomatic disorder, but additional signs may be present. We analyzed postural sway in 19 patients with classic ET and in 19 sex- and age-matched normal controls (NC) to uncover possible abnormalities of balance control. Static posturography was performed with eyes open (EO) and closed during quiet stance and during performance of mental calculation or motor sequence of thumb opposition to the other fingers. No significant differences of center of foot pressure (COP) parameters were observed between patients and controls during quiet standing. Visual deprivation induced a similar worsening of postural sway in both groups. Concomitant performance of a cognitive or motor task did not affect COP area, whereas COP path was significantly modified by the cognitive task in both groups. In all EO conditions, the COP path was significantly lower in NC than in ET, but such offset was related only to the group of ET patients with head tremor. This study demonstrates that balance control is only minimally affected in ET, although patients with head involvement and longer disease duration tend to present a reduced postural stability. The "dual-task effect" is less important in ET than in Parkinson's disease patients. © 2005 Movement Disorder Society [source] The effects of Masai Barefoot Technology, footwear on posture: an experimental designed studyPHYSIOTHERAPY RESEARCH INTERNATIONAL, Issue 4 2007Paul New Introduction.,This study was approved by the University of Southampton Ethics Committee. The aim of the study was to assess the anatomical changes to upright posture that occur in the sagittal plane as a result of wearing Masai Barefoot Technology (MBT) footwear during standing and walking. MBT claims that its innovative unstable shoes promote a more upright posture in which musculature is strengthened and joint wear reduced (Amann and Amann, 2004). This could be helpful in the management and prevention of conditions such as osteoarthritis and back pain. Method.,Twelve students (six male and six female), aged between 18 and 40 years, at the University of Southampton participated in the study. Participants attended one session at a biomechanics laboratory. The kinematics of posture while wearing MBT shoes during standing and gait were examined, using a two-dimensional motion analysis system, and compared to a control shoe. Statistical significance was tested by use of a paired t -test and a Wilcoxon signed-ranks test. Results.,Students standing in MBT footwear demonstrated a statistically significant increase in plantar flexion at the ankle joint (p = 0.025; mean flexion 3.02°; 95% confidence interval [95% CI] ,5.6 to ,0.4). Walking in MBT shoes showed a decrease in trunk flexion (p = 0.007; mean flexion 1.44°; 95% CI ,2.4 to ,0.4) and a reduction in anterior tilt of the pelvis (p = 0.003; mean tilt 3.20°; 95% CI ,5.06 to ,1.35) at heel strike. At toe-off a significant reduction in anterior pelvic tilt (p = 0.035; mean tilt 2.35°; 95% CI) was found in the MBT shoes. There was no significant difference found between the two shoe conditions at mid-stance, pelvic tilt (p = 0.53; mean tilt 1.83 degrees) trunk flexion (p = 0.05; mean flexion 0.95 deg). Conclusion.,MBT footwear changes certain characteristics of posture in quiet standing and walking. These findings could have positive implications for the management of conditions such as osteoarthritis and back pain; however, further research is needed. Copyright © 2007 John Wiley & Sons, Ltd. [source] Body Movement Induced by Electrical Stimulation of Toe Muscles During StandingARTIFICIAL ORGANS, Issue 1 2008Xavier Tortolero Abstract:, The purpose of this study was to investigate whether artificially induced muscle contractions of toe muscles using functional electrical stimulation (FES) would cause center of pressure (COP) displacement and corresponding body acceleration. Ten able-bodied subjects were asked to stand still on force plates. The flexor digitorum brevis and the flexor hallucis brevis in both legs were simultaneously stimulated using a transcutaneous FES device. The muscles were stimulated 20 times at random intervals with four different stimulation intensities. We demonstrated that the toe muscle activity induced by electrical stimulation evoked COP displacement, which generated body acceleration. As expected, a larger stimulation induced a larger COP movement and acceleration. Therefore, we propose the use of FES-induced contractions of the toe muscles as a means to control balance during FES-assisted quiet standing. Spinal cord-injured and severe-stroke patients could benefit from this electrical stimulation technique for improving FES-assisted standing. [source] | ||||||||||