Efficient Postural Control Research Articles

Sensorimotor recalibration of postural control strategies occurs after whole body vibration

Efficient postural control results from an effective interplay between sensory feedbacks integration and muscle modulation and can be affected by ageing and neuromuscular injuries. With this study, we investigated the effect of whole-body vibratory stimulation on postural control strategies employed to maintain an upright posture. We explored both physiological and posturography metrics, through corticomuscular and intramuscular coherence, and muscle networks analyses. The stimulation disrupts balance in the short term, but leads to a greater contribution of cortical activity, necessary to modulate muscle activation via the formation of (new) synergies. We also observed a reconfiguration of muscle recruitment patterns that returned to pre-stimulation levels after few minutes, accompanied by a slight improvement of balance in the anterior–posterior direction. Our results suggest that, in the context of postural control, appropriate mechanical stimulation is capable of triggering a recalibration of the sensorimotor set and might offer new perspectives for motor re-education.

Analysis of pain intensity and postural control for assessing the efficacy of shock wave therapy and sonotherapy in Achilles tendinopathy – A randomized controlled trial

BackgroundThe troublesome symptoms of Achilles tendinopathy prompt patients to seek effective forms of conservative treatment. The main aim of the study was to determine the therapeutic efficacy of shock wave and ultrasound therapies for Achilles tendinopathy in reducing pain intensity. Treatment efficacy was also assessed using objective posturographic measurements. MethodsThirty-nine patients patients were randomly allocated to one of three experimental groups that received shock wave therapy (group A), ultrasound therapy (group B) and placebo ultrasound (group C). Posturographic measurements and subjective assessment of pain intensity were taken prior to therapy and at weeks 1 and 6 of therapy completion. FindingsA comparison of percentage change in activity-related pain from baseline to 6 weeks post-therapy revealed a significantly greater pain reduction in group A compared to group B. The three-way ANOVA demonstated an effect of treatment type on all posturographic variables. The Bonferroni post-hoc test showed the means of all variables were significantly smaller for group A than group B. Limb condition also had an effect on the center-of-pressure trajectories in anteroposterior plane; the post-hoc test showed the mean values of the variables were significantly greater for the non-affected compared to affected limb. InterpretationShock wave therapy was significantly more effective than sonotherapy for alleviation of activity-related pain of Achilles tendinopathy. An association was also shown between shock wave therapy and more efficient postural control in patients with Achilles tendinopathy. The parameters of center-of-pressure trajectories in the sagittal plane were significantly greater for the non-affected compared to affected limb.The trial was prospectively registered in the Australian and New Zealand Clinical Trials Registry (no. ACTRN12617000860369; registration date: 9.06.2017).

Evaluating Oculomotor Tests before and after Vestibular Rehabilitation in Patients with Parkinson's Disease: A Pilot Pre-Post Study.

Introduction The elderly population is commonly affected by balance and gait disorders that increase the risk of falls. Pivotal systems for efficient postural control are sensory, motor, visual, vestibular, and cognitive. Disruption in any of these systems could lead to postural instability. Vestibular rehabilitation is a set of exercises that positively affect the primary components of the central sensory-motor integration, including somatosensory, visual, and vestibular systems. Accordingly, we hypothesized that vestibular rehabilitation exercises might improve both oculomotor functions and upright postural control in patients with Parkinson's disease. Materials and Methods 11 idiopathic Parkinson's patients voluntarily participated in this study based on inclusion criteria: central vestibular dysfunction and the Hoehn and Yahr scale scores less than or equal to 3. Videonystagmography (VNG) and the Berg Balance Scale (BBS) scores were measured at the baseline. Then, the patients underwent vestibular rehabilitation training for 24 sessions (3 sessions per week). The VNG and BBS were measured again after 48 hours of the completion of the last session of the training. Result After completing vestibular rehabilitation sessions, there were significant improvements in balance (P ≤ 0.001). Eye-tracking and gaze function statistically improved in 7 patients and 6 patients, respectively. Conclusion Vestibular rehabilitation produced positive effects on oculomotor function and balance in a small cohort of people with PD. Consequently, it could be considered as a possible effective intervention for Parkinson's patients. This trial is registered with IRCT201709123551N6.

Identifying patterns in trunk/head/elbow changes of riders and non-riders: A cluster analysis approach

Correct rider oscillation and position are the basics for a good horseback riding performance. In this paper, we propose a framework for the automatic analysis of athletes behaviour based on cluster analysis. Two groups of athletes (riders vs non-riders) were assigned to a horseback riding simulator exercise. The participants exercised four different incremental horse oscillation frequencies. This paper studies the postural coordination, by computing the different discrete relative phases of head-horse, elbow-horse and trunk-horse oscillations. Two clustering algorithms are then applied to automatically identify the change of rider and non-rider behaviour in terms of postural coordination. The results showed that the postural coordination was influenced by the level of rider expertise. More diverse behaviour was observed for non-riders. At the opposite, riders produced lower postural displacements and deployed more efficient postural control. The postural coordination for both groups was also influenced by the oscillation frequencies.

Does the transcranial direct current stimulation improve dual-task postural control in young healthy adults?

Some studies have suggested that postural balance improved after a single session of transcranial direct current stimulation (tDCS), whereas others have found minimal, if any, effects on postural performance. To address the issue of replication in tDCS studies, we re-tested the anodal tDCS effects of left dorsolateral prefrontal cortex while performing a dual-task by increasing the attentional demands associated with more challenging proprioceptive conditions. Twenty-four young adults (mean age: 21.3 ± 1.2years) were randomly divided into two groups (a "real tDCS" vs. a "sham tDCS" group) were asked to maintain a quiet stance on a force platform. Eight trials were conducted, with eyes open and eyes closed, standing on a firm and foam surface and performing a simple and dual-task (backward counting). The postural performance was assessed by various centre-of-pressure parameters before and immediately after a 20-min tDCS session. No main effect of group and no interaction considering this factor were observed, regardless of the centre-of-pressure variables (all p values > 0.1). No evidence of a more efficient postural control emerged after a tDCS session. Beyond promising research on tDCS to maximize cognitive and behavioural enhancement, the current results indicate that caution needs to be taken when drawing firm conclusions, at least in young healthy adults.

Action observation improves sit-to-walk in patients with Parkinson's disease and freezing of gait. Biomechanical analysis of performance

IntroductionFreezing of gait (FoG) is one of the most disabling gait disorders in Parkinson's disease (PD), reflecting motor and cognitive impairments, mainly related to dopamine deficiency. Recent studies investigating kinematic and kinetic factors affecting gait in these patients showed a postural instability characterized by disturbed weight-shifting, inappropriate anticipatory postural adjustment, worse reactive postural control, and a difficulty executing complex motor tasks (i.e. sit-to-walk). These symptoms are difficult to alleviate and not very responsive to Levodopa. For this reason, additional therapeutic actions based on specific therapeutic protocols may help patients with their daily lives. We conducted a randomized control trial aimed to test if two clinical protocols for PD patients with FoG were effective to improve postural control. MethodsRehabilitation protocols, conceived to improve gait, were based on learning motor exercises with the Action Observation plus Sonification (AOS) technique, or by the use of external sensory cues. We collected biomechanical data (Center of Mass COM, Center of Pressure COP, and moving timings), using the sit-to-walk task as a measure of motor and gait performance. ResultsKinetic and kinematic data showed that when treatment effects consolidate, patients treated with AOS protocol are more efficient in merging subsequent motor tasks (sit-to-stand and gait initiation), and diminished the total moving time and the area of the COP positions. ConclusionWe demonstrated for the first time that PD patients with FoG treated with an AOS protocol aimed at relearning appropriate gait patterns increased balance control and re-acquired more efficient postural control.

Differences in Lower Limb Muscle Activation and Centre of Pressure Movement Between Expert Workers and Novices in Simulated Maritime Environments

OCCUPATIONAL APPLICATIONS Better understanding of lower limb muscle activations and habituation processes has implications for injury prevention. This study examined the influence of repeated exposures to simulated wave motions on lower limb muscle activity. Our findings suggest that, at least while standing, novice maritime workers can quickly adapt their lower extremity muscle activity and, to a lesser extent, their center of pressure movement, so that is similar to expert maritime workers. These decreases in muscle activations with repeated exposures suggest that individuals can adapt rapidly to the motions to decrease muscle fatigue and the risk of falling. Such information should therefore be considered when developing ergonomic interventions for maritime occupations such as ship design and training for new workers.TECHNICAL ABSTRACT Background: Work in moving environments, such as maritime workplaces, exposes workers to unique neuromuscular control challenges that may increase risk of falls or fatigue-related injury. Purpose: The purpose of this study was to determine if muscle activations differ based on previous experience working in a moving environment and/or with repeated exposure to the same motions. Methods: Twelve individuals with no maritime work experience, and 14 individuals with maritime work experience, were exposed to five 5-minute trials of simulated maritime motion. Electromyography (EMG) was collected bilaterally from several lower-extremity muscles and center of pressure was collected using a pressure mat over the full duration of all of the trials. EMG data were normalized to maximal voluntary isometric contractions (MVICS) collected before the trials, and then compared between groups and trials. Results: Muscle activation in both groups significantly increased with motion exposure, however the activation amplitudes were lower in the experienced (346% increase) vs. the novice group (542% increase). With repeated exposure to the five motion trials, muscle activations for all individuals gradually decreased from trial 1 (∼5–15%MVIC) to trial 5 (∼1.5–4.5%MVIC).Conclusions: While all individuals demonstrated adaptations with repeated exposures, those with experience working in maritime environments adopted postural responses that required substantially less activation of the lower limb muscles. This difference may be due, at least in part, to these individuals having adapted postural control strategies to optimize stability. The decrease in muscle activation observed with repeated exposure to the motion profile suggests that individuals can adapt rapidly to the destabilizing nature of the motion profiles, implying that they are learning to adopt more efficient postural control strategies.

Postural Control: Learning to Balance Is a Question of Timing

A new study shows that, in zebrafish, efficient postural control is developed by larvae as they learnthecorrective movements required to maintain an unstable posture and overcome changes in body inertia.

Older adults utilize less efficient postural control when performing pushing task

The ability to maintain balance deteriorates with increasing age. The aim was to investigate the role of age in generation of anticipatory (APA) and compensatory (CPA) postural adjustments during pushing an object. Older (68.8±1.0years) and young adults (30.1±1.4years) participated in the experiment involving pushing an object (a pendulum attached to the ceiling) using both hands. Electrical activity of six leg and trunk muscles and displacements of the center of pressure (COP) were recorded and analyzed during the APA and CPA phases. The onset time, integrals of muscle activity, and COP displacements were determined. In addition, the indexes of co-activation and reciprocal activation of muscles for the shank, thigh, and trunk segments were calculated. Older adults, compared to young adults, showed less efficient postural control seen as delayed anticipatory muscle onset times and delayed COP displacements. Moreover, older adults used co-activation of muscles during the CPA phase while younger subjects utilized reciprocal activation of muscles. The observed diminished efficiency of postural control during both anticipatory and compensatory postural adjustments observed in older adults might predispose them to falls while performing tasks involving pushing. The outcome provides a background for future studies focused on the optimization of the daily activities of older adults.

Balance characteristics in patients with major depression after a two-month walking exercise program: A pilot study

Recent studies have demonstrated impaired balance performance in patients with major depressive disorder (MDD) in comparison to healthy controls (HC), which is likely to be related to deficits in integration of visual and proprioceptive inputs necessary for efficient postural control. In parallel, considerable literature supports the positive effects of a walking program on depressive symptoms. Thus this study aimed to determine the effects of a two-month walking program on implicit postural control strategies in MDD. Compared with twelve age- and body mass index-matched non-psychiatric HC (mean age 50.41±6.93 years; five women), nine MDD (mean age 51.88±10.01 years; five women) performed two sessions of standing postural control assessment, separated by eight weeks of the walking program, while the HC were only assessed at t0. The walking program included one-hour supervised walking sessions, three times a week over a two-month period. Postural performance was assessed by various center of pressure (COP) parameters, in particular those that bound the COP velocity of postural sway. The primary findings were that MDD patients exhibited positive physical activity-related changes in postural performance, with a decrease in body sway in the most difficult condition (with a foam surface). The real impact of the walking program on COP velocity-based variables suggests that MDD patients improved their ability to make more efficient postural corrections, which is useful for daily activities and autonomy. A balance assessment in the clinical screening routine might be used as a new index of the effectiveness of walking programs recommended for people with depression.Trial registration: This study is registered at http://clinicaltrials.gov/: NCT01995422.

Effects of Balance Training on Muscle Coactivation During Postural Control in Older Adults: A Randomized Controlled Trial

Recently, several studies have reported age-associated increases in muscle coactivation during postural control. A rigid posture induced by strong muscle coactivation reduces the degree of freedom to be organized by the postural control system. The purpose of this study was to clarify the effect of balance training on muscle coactivation during postural control in older adults. Forty-eight subjects were randomized into an intervention (mean age: 81.0 ± 6.9 years) and a control group (mean age: 81.6 ± 6.4 years). The control group did not receive any intervention. Postural control ability (postural sway during quiet standing, functional reach, and functional stability boundary) was assessed before and after the intervention. A cocontraction index was measured during the postural control tasks to assess muscle coactivation. Cocontraction index values in the intervention group significantly decreased following the intervention phase for functional reach (p < .0125). Cocontraction index values had a tendency to decrease during functional stability boundary for forward and quiet standing tasks. Functional improvements were observed in some of the tasks after the intervention, that is, functional reach, functional stability boundary for forward, one-leg stance, and timed up and go (p < .05). Our study raised the possibility that balance training for older adults was associated with decreases in muscle coactivation during postural control. Postural control exercise could potentially lead older adults to develop more efficient postural control strategies without increasing muscle coactivation. Further research is needed to clarify in greater detail the effects of changes in muscle coactivation.

Cardio-postural deconditioning: A model for post-flight orthostatic intolerance

Post-flight astronauts experience temporary but sometimes severe postural control dysfunction and decreased orthostatic tolerance. Research points to a possible link between cardiovascular and postural controls and orthostatic tolerance [Claydon,V.E., Hainsworth, R., 2006. Postural sway in patients with syncope and poor orthostatic tolerance. Heart 92, 1688-1689], for which a neurophysiological model has been presented [Souvestre, P.A., Blaber A.P., Landrock C.K., 2008. Space motion sickness: the sensory-motor controls and cardiovascular correlation. Acta Astronautica 63, 745-757]. To validate this model, young and elderly subjects (n=12) were compared with respect to postural mediolateral sway (ML sway) and blood pressure (BP) during quiet standing. Both groups had a peak in the low frequency region (0.03-0.07Hz) of cross-spectral power between ML sway and BP; however, only the young subjects had signal coherence greater than 0.5. Short-range Hurst coefficient from Stabilogram Dynamic Analysis was significantly lower for ML sway in young (0.694+/-0.068) compared to elderly subjects (0.812+/-0.10) (p=0.028). Young subjects were better able to command a closed-loop strategy of motor-control providing a more efficient postural control. Further application of this model with astronauts could lead to further understanding of post-flight orthostatic intolerance.