Sensorimotor changes such as postural and gait instabilities can affect the functional performance of astronauts after gravitational transitions. When astronauts are trained before flight with supra-threshold noisy, stochastic vestibular stimulation (SVS), the central nervous system can be trained to reweight sensory information by using veridical information from other sensory inputs (such as vision and proprioception) for postural and gait control. This reweighting, in turn, can enhance functional performance in novel gravitational environments. However, the optimal maximum amplitude of stimulation has not yet been identified that can simulate the effect of deterioration in vestibular inputs for preflight training or for evaluating vestibular contribution in functional tests in general. Most studies have used arbitrary but fixed maximum current amplitudes from 3 to 5 mA in the mediolateral (ML) direction to disrupt balance function in both ML and anterior-posterior directions in healthy adults. The goal of this study was to determine the minimum SVS level that yields an equivalently degraded balance performance. Fourteen subjects stood on a compliant surface with their eyes closed and were instructed to maintain a stable upright stance. Measures of stability of the head, trunk, and whole body were quantified in the ML direction. Objective perceptual motion thresholds were estimated ahead of time by having subjects sit on a chair with their eyes closed and giving 1-Hz bipolar binaural sinusoidal electrical stimulation at various current amplitudes. Results from the balance task suggest that using stimulation amplitudes of 280% of motion-perceptual threshold (~2.2 mA on average) significantly degraded balance performance.

Listed In: Biomechanics, Neuroscience, Posturography

Dance May Improve Quality of Life But Not Gait in Individuals with Parkinson’s Disease

Purpose: Research supports the use of ballroom dance to improve balance in individuals with Parkinson’s disease (PD). This study used the Mark Morris Dance for PD program as a template for dance classes to examine the effects of dance on gait, balance, and quality of life in individuals with PD. Subjects : Eleven individuals with mild to moderate PD participated in the study. Methods : A trained instructor led dance classes for subjects once a week for 12 weeks. Participants were encouraged to use the Mark Morris Dance for PD At Home DVD twice a week for 45 minutes. Classes included a 20 min. seated warm up; a 20 min. supported standing portion focused on balance and strength; and 30 min. partnered movements for swing, shag, or tango. Data collected before and after the intervention included gait parameters (Protokinetics Zeno walkway), sway area (AMTI force platform) during mCTSIB, Mini-BESTest, Falls Efficacy Scale, Apathy Scale and PDQ-39. A paired-samples t-test was performed. Results : Participants had significant decrease in apathy following the intervention (P = 0.018). A significant decrease in the percentage of the double support phase of gait indicated individuals spent less time with both feet in contact with the ground (P = 0.019). Conclusions : An instructor-led dance class based on the Dance for PD program once per week for 12 weeks improved certain aspects of quality of life, but not necessarily gait and balance. Further research with increased frequency of supervised dance classes is indicated.
Listed In: Gait, Neuroscience, Physical Therapy

Sensory contributions to standing balance in unilateral vestibulopathy

Patients with unilateral peripheral vestibular disorder (UPVD) have diminished postural stability and therefore the aim of this study was to examine the contribution of multiple sensory systems to postural control in UPVD. Seventeen adults with UPVD and 17 healthy controls participated in this study. Centre of pressure (COP) trajectories were assessed using a force plate during six standing tasks: Forwards and backwards leaning, and standing with and without Achilles tendon vibration, each with eyes open and eyes closed. Postural stability was evaluated over 30s by means of: total COP excursion distance (COPPath) and the distances between the most anterior and posterior points of the COPPath and the anterior and posterior anatomical boundaries of the base of support (COPAmin and COPPmin). In addition, the corrected COPAmin and COPPmin was assessed by taking the corrected base of support boundaries into account using the anterior and posterior COP data from the leaning tasks. UPVD patients showed a tendency for smaller limits of stability during the leaning tasks in both directions. Subject group and task condition effects were found (P<0.05) for COPPath, (i.e. higher values for patients compared to controls). UPVD patients showed lower (P<0.05) COPPmin values compared to the control group for all conditions (more pronounced with the corrected COPPmin). Disturbance of the visual system alone lead to a distinct postural backward sway in both subject groups which became significantly more pronounced in combination with Achilles tendon vibration. The individual limits of stability should be considered in future research when conducting posturographic measurements.
Listed In: Biomechanics, Neuroscience, Physical Therapy, Posturography