By Phuong Lisa Ha & Mathew Debenham,

Standing balance is important for tasks of daily living, and involves the complex integration of sensorimotor signals within the central nervous system. With aging, standing balance performance declines alongside strength and power. Age-related decrements within the vestibular system (e.g., impairment in vestibular hair cell receptors) could lead to a failure in properly detecting head motion and further impair postural control. There is some evidence that in response to age-related decline in the peripheral vestibular system function, the central nervous system increases its sensitivity to enhance vestibular-driven reflexes for gaze stabilization and maintaining balance. Additionally, following fatiguing ankle flexor exercise, young males appear to have increased vestibular-evoked balance responses, which may be a compensatory strategy for the reduced strength of the ankle muscles. Yet, it is unclear if age-related muscle weakness also increases the sensitivity of the vestibular control of balance, similarly to exercise-induced muscle weakness.

To answer this question, we evaluated knee extensor muscle strength and power in eight young (20-24 years old) and eight older females (63-76 years old). On a separate visit, we assessed their balance in response to vestibular stimulation; we applied a small electrical current on the mastoid processes (just behind the ear) while participants stood quietly on a force plate for two, 90-s trials. We recorded anterior-posterior ground reaction forces and muscle activity of the dorsi- and plantar flexors.

Figure: Assessment protocol; left: lower limb strength testing; right: quiet standing trials under vestibular stimulation.

We found that compared to their younger counterparts, older females had weaker and less powerful knee extensor muscles. They also exhibited larger vestibular-evoked balance responses, which were associated with increased muscle activity in the dorsiflexors, but not plantar flexors. The vestibular-evoked balance response was also significantly correlated with maximal knee extensor power.

In conclusion, we suggest that the larger vestibular-evoked balance responses in older females may be linked to a compensatory strategy that uses greater activation of the dorsiflexors to stabilize, at least, in part, for age-related reductions in knee extensor power.

Publication

Ha, P. L., Peters, W. B., McGeehan, M. A., & Dalton, B. H. (2022). Age-related reduction in peak power and increased postural displacement variability are related to enhanced vestibular-evoked balance responses in females. Experimental gerontology, 111670. https://doi.org/10.1016/j.exger.2021.111670

About the Author

By Dr Nidhi Seethapathi.

Even without external perturbations such as pushes or uneven terrain, noise-like imperfections in biological signals continuously perturb animals when they move. In this paper, we inquire how humans run without falling down in the presence of such intrinsic perturbations. We know that such intrinsic perturbations manifest as step-to-step variability and that this variability serves as a metric to quantify stability of movement. However, we understand little about the relationship between this step-to-step variability and motor control. Moreover, human running is most commonly modeled as a spring-and-mass or its variants, which are pertinent for understanding the role of passive actuation in running but don’t explain how deviations from the average motion are corrected. In this work, we explain how humans run without falling down in the presence of intrinsic noise-like perturbations with the help of experiments and investigate the role of active control in stable running in simulation.

We measured step-to-step variability in the motion and ground reaction forces while subjects ran on a treadmill. Next, we mined this variability to understand the relationship between input deviations from the average center of mass states during flight, and output deviations from average foot placement and ground reaction forces in the next stance phase. We discovered that deviations occurring in center of mass velocities at flight are mostly corrected within the next step and this control is tighter for sideways than for fore-aft deviations. Deviations in center of mass height are corrected by shifting the peak of the ground reaction force during stance. The changes in the center of mass motion predict changes in foot placement, in advance of the foot predicting its own placement, and the corresponding time lag allows for the presence of active feedback. We implemented these experimentally discovered control strategies on a simple biped model with muscle-driven actuation and found that it runs without falling down in the presence of large discrete perturbations (see videos below) as well as small continuous perturbations (of the type present in the experiment). Our results suggest that the muscles play an important role in controlling continuous intrinsic perturbations.

The methods used in this work provide a template for analyzing how running is controlled without the need for external perturbations. These methods could be used to further investigate the role of active feedback control by repeating the study with weakened vestibular and visual feedback. These methods could also be applied to different populations, such as athlete vs. non-athlete, to see how they differ in the control strategies used. The real-to-simulation controller we have developed here can be implemented on bipedal robots and exoskeletons to control running using human-derived gains.

Videos: The model with experimentally-derived gains is stable to discrete perturbations (larger than those present in the experiment).

Publication

Seethapathi, Nidhi, and Manoj Srinivasan. “Step-to-step variations in human running reveal how humans run without falling.” eLife 8 (2019): e38371. https://elifesciences.org/articles/38371

About the Author

By Dr Brian Dalton.

The central nervous system produces motor responses to maintain standing balance through complex processing and integration of multiple signals regarding the position and motion of the body in space. Activation of trunk, leg and foot muscles contribute to whole-body balance control to varying degrees. Even though the feet provide an excellent source of sensory information, it is uncertain whether foot muscles play an active functional role in maintaining quiet standing balance; or whether the activity of these muscles is simply a by-product of preserving rigidity of the feet for the plantar flexors to produce postural responses to keep the body upright. Electrical vestibular stimulation (EVS) can be used to evoke whole-body balance responses that arise from the summation of all muscles involved in the compensatory response. The presence of vestibular-evoked balance responses can elucidate the specific muscle’s role during standing. Thus, the purpose of our study was to determine whether foot muscles – specifically, the abductor hallucis (AH) and abductor digiti minimi (ADM) – displayed postural responses driven by vestibular stimulation during quiet standing.

Seven healthy, young participants were exposed to a continuous, random EVS signal during quiet standing (Figure below). We assessed postural responses as variations in anterior-posterior forces under the feet, and AH, ADM, and medial gastrocnemius muscle activity using surface electromyography. We characterised the relationships between the EVS input and subsequent motor output in both time and frequency domains via multivariate Fourier analyses. We found that vestibular-evoked balance responses were present in anterior-posterior forces and in all muscles. These responses were modified similarly via head orientation (affecting the direction of EVS-evoked balance responses) and removal of vision (affecting the weighting of sensory information), which is characteristic of a postural adjustment driven by vestibular stimulation. The current findings emphasize that foot muscles provide an active role in balance control during standing.

Our results indicate that a complete model of the sensorimotor control of quiet standing should include foot muscles. Future research should focus on examining whether decrements within foot muscles lead to impairments in standing, and whether rehabilitative strategies involving these muscles can improve postural control in those with standing balance problems.

Figure: Experimental setup

Publication

Wallace JW, Rasman BG, Dalton BH. Vestibular-evoked responses indicate a functional role for intrinsic foot muscles during standing balance. Neurosci 377: 150-160, 2018.

https://doi.org/10.1016/j.neuroscience.2018.02.036

About the Author

Freezing of gait (FOG) is a very disabling symptom of Parkinson’s disease (PD). Therefore, several maneuvers to preserve gait or to support taking steps after FOG onset are of great interest to clinicians and patients. Since impaired proprioceptive processing is considered a contributing factor to FOG, we asked: would enhanced proprioceptive stimuli reduce FOG severity? We used tendon vibration to stimulate the proprioceptive system via activation of muscle spindles. The aim of this study was to verify the effects of tendon vibration on FOG severity, when used as a preventive and rescue strategy.

To induce FOG episodes, sixteen individuals known to experience FOG (so-called freezers) walked with small steps on a pressure-sensing mat. Custom-made devices were used to provide Achilles tendon vibration (100 Hz, amplitude of 1.0 mm) whenever a FOG episode was detected (1^stepisode) to test its utility as rescue strategy. Since we did not turn-off vibration until the end of the trial, we could evaluate its effects as a preventive strategy on subsequent FOG episodes. We compared the effect of tendon vibration between stimulation of the leg that was least (LA) or most affected (MA) by PD symptoms. A condition without tendon vibration (OFF) was also collected as baseline. Our results show that tendon vibration successfully alleviated FOG severity when used as a rescue strategy during the 1^st episode. However, this was only true when the LA limb was stimulated (Figure 1A). Vibration influenced the limb used to reinitiate gait after freezing, increasing the number of initiations with the contralateral leg (Figure 1E).Tendon vibration did not reduce FOG severity when used as a preventive strategy, since we observed no differences in the durations of subsequent freezing episodes (Figure 1A, in orange). This was also highlighted by a lack of difference in time between FOG episodes among conditions (Figure 1D).

Our results strengthened the notion that FOG is related to proprioceptive processing deficits. These findings ruled out attentional mechanisms, given that vibration effects were only observed unilaterally and most steps to reinitiate gait were taken with the contralateral leg. Most importantly, this study demonstrated that tendon vibration is a promising technique to alleviate FOG severity in individuals with PD, especially in those with mild symptoms. Future research should focus on transferring tendon vibration to clinic practice and test its effects on other modalities of freezing.

Figure. A: Mean (SE) tendon vibration effects on first (blue) and subsequent (orange) freezing episodes per condition. OFF: no vibration; MA: most-affected limb; LA: least-affected limb. Vertical black line refers to significant differences between conditions; B and C:  Description of walking sections analysed in the study; D: Mean (SE) time between freezing episodes per condition; E: percentage of steps used to re-initiate gait per limb.

Publication

Pereira MP, Gobbi LT, Almeida,QJ. Freezing of Gait in Parkinson’s disease: Evidence of sensory rather than attentional mechanisms through muscle vibration. Parkinsonism Relat Disord, v. 29, p. 78-82, Aug 2016. ISSN 1873-5126. doi: 10.1016/j.parkreldis.2016.05.021.

About the Author

In humans, gait initiation is particularly challenging for motor and postural control. While standing on only two legs, we have to move our whole body forward and pass from a (relatively) stable (double leg stance) to an (very!) unstable position (single leg stance). This process is associated with anticipatory postural adjustments (APAs). The neural substrates for generating these APAs and initiating a step are not fully known. By applying repetitive transcranial magnetic stimulation (rTMS), we can manipulate APAs. Previous research showed that rTMS applied above the supplementary motor area provokes a shortening of the APA duration of the first step with no change in APA amplitude and rTMS applied over the cerebellum affects spatial characteristics of walking during locomotor adaptation. This study extends this research further by looking at the effects of supplementary motor area and cerebellar stimulation on the generation of APAs and gait initiation.

We selectively disrupted the supplementary motor area and cerebellum with continuous theta burst rTMS (cTBS, 600 stimuli, three-pulse bursts at 50 Hz, repeated every 200 ms continuously for 40 s-5 Hz) and evaluated the effects of the stimulation on the APAs and execution phases of gait initiation. We recorded biomechanical parameters of gait initiation and EMG activity of the lower leg muscles in 22 healthy volunteers. Our volunteers were instructed to walk at their usual self-paced speed for 10 trials before and after rTMS. They performed separate sessions in a randomised order for rTMS over the supplementary motor area, cerebellum and sham stimulation (to either supplementary motor area or cerebellum), the sessions being separated at least 7 days. We found that functional inhibition of the supplementary motor area led to a shortened APA phase duration with advanced and increased muscle activity. During execution, it also advanced muscle co-activation and decreased the duration of stance soleus activity. Functional inhibition of the cerebellum on the other hand did not influence the APA phase duration and amplitude. During execution, it did increase muscle co-activation and decreased execution duration with increased swing soleus muscle duration and activity. Neither SMA nor cerebellar functional inhibition provoked significant changes in the step length and velocity or postural control during gait execution (i.e. double stance duration and braking index).

The results support distinct roles for the supplementary motor area and the lateral posterior cerebellum in human gait initiation. The supplementary motor area is important for the timing and amplitude of the preparatory phase of the gait initiation, and the posterior cerebellum contributes to the inter- and intra-limb muscle coordination, and probably coupling between the APAs and the execution phases. This study enhances our understanding of how the cortico-pontine-cerebello-thalamo-cortical pathway contributes to the preparation and the execution of the first step in humans.

Figure – Effects of cTBS SMA and sham stimulation on gait initiation in an individual subject. Note that after SMA stimulation (left panel) the duration of the anticipatory postural adjustments phase (delay between t0 and FC) decreased with an advanced TA muscle activity. Such is not the case after sham stimulation (right panel).

Publication

Richard A, Van Hamme A, Drevelle X, Golmard JL, Meunier S, Welter ML. Contribution of the supplementary motor area and the cerebellum to the anticipatory postural adjustments and execution phases of human gait initiation. Neuroscience. 2017 Sep 1;358:181-189. doi: 10.1016/j.neuroscience.2017.06.047. Epub 2017 Jul 1. PMID: 28673716 (http://www.sciencedirect.com/science/article/pii/S0306452217304529?via%3Dihub)

About the Author

Both animals and humans can change their gait speed over a wide range to suit the situation. The coordinated locomotor muscle activity among various speeds is mainly generated by the spinal central pattern generators (CPGs). Recent animal studies have demonstrated the following two characteristics of the speed control mechanisms of the spinal CPGs: (i) rostral spinal segment activation is essential to achieving high-speed locomotion; and (ii) different spinal neural modules are sequentially activated with increasing speed. To examine whether similar control mechanisms exist in the spinal cord of humans, we estimated spinal neural activity during varied-speed locomotion from surface electromyographic (EMG) signals.

We recorded EMG activity from 14 lower leg muscles during a range of speeds (from very slow walking [0.3 m/s] to fast running [4.3 m/s]). We estimated spinal neural activity by mapping the EMG activations onto the estimated location in the spinal cord based on innervation relationships between muscles and spinal segments (Fig. 1A-2). We then broke down the spinal activities into fundamental units of the activity generated by each locomotor module (i.e., muscle synergy) (Fig. 1A-3). We found that the reconstructed spinal activity patterns were divided into the following three patterns depending on the locomotion speed: slow walking, fast walking and running (Fig.1B, the first column). During these three activation patterns, the activity in rostral segments was more increased than that in caudal segments as speed increased. Additionally, the different spinal activation patterns were generated by distinct combinations of locomotor modules (Fig.1B, second and subsequent columns). Most modules newly recruited in fast walking and running were activated by the upper lumbar segments.

Figure 1. (A) Procedures of reconstruction of spinal activity patterns from surface EMG signals. (B) Reconstructed spinal activity patterns (the first column) are divided into several locomotor modules (second and subsequent columns from the left) at slow walking, fast walking and running. The locomotor modules were obtained by non-negative matrix factorization method. Muscle weighting component (top bars) and its corresponding temporal pattern component (the same color waveform) for each locomotor module is also shown in the figure.

To summarize the results, we found the following spinal activation patterns regarding speed control of human locomotion: (i) spinal activity in the rostral segments increased compared with the caudal segments with increasing locomotion speed; and (ii) the different spinal activation patterns recruited distinct combinations of locomotor modules. These results are consistent with the speed control characteristics of vertebrate CPGs. This commonality supports a hypothesis that basic locomotor neural circuits are highly conserved among in humans, mammals, and birds over vertebrate evolution. Our results provide fascinating insight into not only human locomotor control but also the evolution of vertebrate locomotion.

Publication

Yokoyama H, Ogawa T, Shinya M, Kawashima N, Nakazawa K (2017). Speed dependency in α-motoneuron activity and locomotor modules in human locomotion: indirect evidence for phylogenetically conserved spinal circuits. Proc Roy Soc B. 284(1851), 20170290. doi: 10.1098/rspb.2017.0290.
Link: http://dx.doi.org/10.1098/rspb.2017.0290

About the Author

During walking, we rely on visual information to identify tripping hazards and navigate safely through the environment. The way we shift our gaze and scan the environment (our visual-search behaviour) is affected by ageing and fall risk. Older adults at high-risk of falling will transfer their gaze away from a stepping target before the step has been completed (i.e., prior to heel contact); a behaviour which is causally linked to reduced stepping accuracy. Moreover, when navigating a series of stepping constraints, high-risk older adults will adopt a less-variable pattern of visual-search, whereby their gaze is fixated predominately on the initial stepping target, at the expense of upcoming obstacles or targets. We hypothesised that this maladaptive and less-variable pattern of visual-search behaviour may be caused by inefficiencies in attentional processing, with high-risk older adults possessing insufficient cognitive resources to generate and store a ‘spatial map’ of their environment. Insufficient cognitive resources for attentional processing during walking may be due to psychological factors. When anxious or following injury or accident (e.g., falls), individuals may attempt to consciously monitor and control movements, which are usually considered largely ‘automatic’. This phenomenon is frequently described as ‘reinvestment’. It is believed that cognitive resources are required to consciously attend to the process of walking, which would limit the resources available for other processes, such as proactively scanning one’s environment. Yet, little is known about how either cognitive load or reinvestment influence visual-search behaviour during walking.

Younger adults traversed a non-linear path (containing two precision stepping targets) while performing a secondary serial-subtraction task and wearing a gaze-tracker unit. Outcome measures included gaze behaviour, stepping accuracy, and time to complete the walking task. When walking while simultaneously carrying out the serial-subtraction task, participants visually fixated on task-irrelevant areas ‘outside’ the walking path more often and for longer durations, and fixated on task-relevant areas ‘inside’ the walkway for shorter durations. These changes were most pronounced in high-trait-reinvesters. The increased task-irrelevant ‘outside’ fixations were accompanied by slower walking times and greater gross stepping errors. Interestingly, these ‘outside’ fixations were temporally related to the performance of the dual-task, with participants more likely to look away from the walkway (or, ‘gaze into thin air’) in the 330ms directly preceding the verbalisation of the dual-task calculation.

Our findings suggest that attention is important for the maintenance of effective gaze behaviours, supporting previous claims that maladaptive changes in visual-search observed in high-risk older adults may be a consequence of inefficiencies within attentional processing. As these changes were most pronounced in high-trait-reinvesters, we speculate that reinvestment-related processes placed additional cognitive demands upon working memory.

Figure. A: An example of a task-relevant ‘inside’ fixation, whereby the participant fixates on an area within their walking path. B: An example of a task-irrelevant ‘outside’ fixation, whereby the participant fixates on an area outside of their walking path. C: Duration (as a percentage of overall fixation durations) of task-relevant ‘inside’ and task-irrelevant ‘outside’ fixations under conditions of Cognitive Load, ** p <.01. D: Number of task-irrelevant ‘outside’ fixations (per second) under conditions of Cognitive Load, * p <.05.

Publication

Ellmers TJ, Cocks AJ, Doumas M, Williams AM, Young WR (2016) Gazing into Thin Air: The Dual-Task Costs of Movement Planning and Execution during Adaptive Gait. PLoS ONE 11(11): e0166063.

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0166063

About the Author

Reflex is the first line of defense for preventing falls when you are perturbed. The reflex system, especially medium-latency or long-latency reflex system, is very flexible and it has been known that the central nervous system takes advantage of prior knowledge about potential upcoming perturbations for modulating postural reflexes. In other words, if you know that may be perturbed, you can prepare for the perturbation. There are two distinct aspects of prior knowledge: spatial and temporal. This study investigated how each of spatial and temporal prior knowledge contributes to the shortening of muscle response latency.

Eleven participants walked on a split-belt treadmill. They were perturbed by sudden and unexpected acceleration or deceleration of the right belt at right foot contact. Spatial prior knowledge was given by verbal instruction of possible direction (only acceleration, only deceleration, or both might occur) of upcoming perturbation at the beginning of an experimental session. Temporal prior knowledge was given to participants by warning tones at foot contact during three consecutive strides before the perturbation. In response to acceleration perturbation, reflexive muscle activity was observed in soleus and gastrocnemius muscles. Onset latency of the gastrocnemius response was shorter (72 ms vs. 58 ms) when participants knew the timing of the upcoming perturbation, whereas the latency was independent no matter whether the participants knew the direction of the perturbation. Soleus latency (44 ms) was not influenced by directional or temporal prior knowledge.

The results suggest that excitability in the supra-spinal neural circuit, which mediates the long-latency reflex, might be enhanced by knowing the timing of the upcoming perturbation. On the other hand, excitability in the spinal neural circuit, which mediates the short-latency reflex, was not influenced by the prior knowledge. Future research should investigate whether it is possible for older people to anticipate both predictable and unpredictable perturbations and find a way to train the Central Nervous Systems to prepare for the postural responses by guessing about potential perturbation.

Publication

Shinya M, Kawashima N, Nakazawa K (2016). Temporal, but not Directional, Prior Knowledge Shortens Muscle Reflex Latency in Response to Sudden Transition of Support Surface During Walking. Front Hum Neurosci. 2016 Feb 8;10:29. doi: 10.3389/fnhum.2016.00029.

https://www.ncbi.nlm.nih.gov/pubmed/26903838

About the Author

Every year about 500,000 people become disabled as a result of spinal cord injuries (SCI). The communication lines between the brain and spinal cord below the injury are cut or dramatically diminished, depending on the severity of the event, which leads to a range of motor disabilities.

It is possible to access the surviving circuits and pathways to alleviate these deficits via epidural electrical stimulation (EES). Walking requires the activation of spatially distributed spinal motor circuits following precise temporal sequences that are continuously adjusted through sensory feedback. Therefore, current neuromodulation therapies – which deliver stimulation to restricted spinal cord locations and remain constant throughout gait execution – are not optimal. In the present work, we argued that targeted stimulation in space and time of the spinal cord, matching the natural dynamics of spinal motor circuit activation, can restore walking and improve motor control after spinal cord injury.

We first conducted anatomical and functional experiments to visualize the spatiotemporal pattern of hindlimb motoneuron activation in intact rats (Figure 1a). We found that walking involves the alternating activation of spatially restricted hotspots underlying extensor versus flexor muscle synergies. We then developed neuromodulation strategies that specifically target proprioceptive feedback circuits in the dorsal roots in order to access these hotspots. Computer simulations determined the optimal electrode locations to recruit specific subsets of dorsal roots. These results steered the design of spatially selective spinal implants and real–time control software to modulate extensor versus flexor muscle synergies with precise temporal resolution adjusted through movement feedback. This conceptually new stimulation strategy reinforced extension versus flexion components for each hindlimb independently and improved a range of important gait features after complete SCI (see Figure 1b).

We considered that spinal implants designed to activate the proprioceptive afferents projecting to the identified flexor and extensor hot spots would engage muscle synergies encoders related to extension and flexion. Our results showed that tailored spinal implants targeting specific subset of dorsal roots with electrodes enabled a gradual control over the degree of flexion and extension on the left and right hindlimbs. Although challenges lie ahead, we believe that spatiotemporal neuromodulation of the spinal cord will become a viable way to accelerate and augment functional recovery in humans with SCI.

Figure 1: Spatiotemporal neuromodulation reproduces the natural pattern of motoneuron activation. From left to right and top to down. (a) Tracer injections into muscles spanning each hindlimb joint, to visualize the spatial location of hindlimb motoneurons. We decomposed the muscle activity during locomotion recorded in all the traced muscles into functional models (muscle synergies). To link muscle synergies to the activation of the burst (‘hotspot’) of motoneuron activity, we extracted the spinal map for each synergy independently. A model of spinal segments showing the temporal sequence underlying the recruitment of muscle synergies and the corresponding activation of extensor and flexor hot spots. (b) Rats received complete SCI at T7 and a spinal implant with conventional midline electrodes (black) and spatially selective lateral electrodes (blue and red). Locomotion in rats on a treadmill without stimulation and with continuous neuromodulation applied over the midline of lumbar and sacral segments (black electrodes) and during spatiotemporal neuromodulation (blue and red electrodes). On the right the results for an intact rat is showed.

Publication

Wenger N, Moraud EM, Gandar J, Musienko P, Capogrosso M, Baud L, Le Goff CG, Barraud Q, Pavlova N, Dominici N, Minev IR, Asboth L, Hirsch A, Duis S, Kreider J, Mortera A, Haverbeck O, Kraus S, Schmitz F, DiGiovanna J, van den Brand R, Bloch J, Detemple P, Lacour SP, Bézard E, Micera S, Courtine G (2016). “Spatiotemporal neuromodulation therapies engaging muscle synergies improve motor control after spinal cord injury.” Nature Medicine. Feb;22(2):138-45. http://www.nature.com/nm/journal/v22/n2/full/nm.4025.html

About the Author

Fear of falling is common in older people. Research studies have reported that people who are more fearful have increased postural sway. However, when fear is experimentally induced, a decrease in postural sway can be observed, due to an adaptive tightening of balance control. These contrasting findings suggest different underlying mechanisms whereby generalised and induced anxiety influence balance control. In our study, we examined the differential effects of previously reported fear of falling and generalised anxiety on standing balance control, during an experiment that induced fear by asking people to stand on an elevated box.

Participants were classified with high or low fall concern using the Falls Efficacy Scale International, as well as high or low anxiety, using the Goldberg Anxiety Scale.  We measured centre of pressure underfoot while participants stood at floor level and on a 65cm elevated box. Non-anxious participants showed an adaptive tightening of balance control in the elevated condition, effectively reducing sway range. The anxious group increased sway frequency but did not constrain sway range (Figure 1). The postural control response to the elevated standing condition was similar for fearful and non-fearful participants.

Our results suggest that older adults with generalised (trait-like) anxiety are less able to appropriately tighten balance control and constrain postural sway in a condition where the potential consequences associated with instability are more hazardous. This is in contrast to young and older adults without anxiety, who show an adaptive tightening of postural control under threatening conditions. This suggests a context-dependent emotional phenomenon interfering with balance control, as postural control changes were not associated with differences in baseline sensorimotor function. Considering the influence of psychological factors (beyond standard clinical examination of concern about falling) may therefore be important when assessing balance and implementing interventions for improving balance in older people.

Publication

Sturnieks DL, Delbaere K, Brodie MA, Lord SR. The influence of age, anxiety and concern about falling on postural sway when standing at an elevated level. Hum Mov Sci. 2016 15;49:206-215

http://www.sciencedirect.com/science/article/pii/S0167945716300902

About the Author