Influence of Postural Anxiety on Postural Reactions to Multi-Directional Surface Rotations

2004 ◽  
Vol 92 (6) ◽  
pp. 3255-3265 ◽  
Author(s):  
M. G. Carpenter ◽  
J. S. Frank ◽  
A. L. Adkin ◽  
A. Paton ◽  
J.H.J. Allum
Keyword(s):  
Angular Displacement ◽  
Center Of Mass ◽  
Trunk Muscles ◽  
Support Surface ◽  
Control Mechanisms ◽  
Postural Reactions ◽  
Postural Threat ◽  
Postural Responses ◽  
Total Body ◽  
Ground Condition

Previous studies have shown significant effects of increased postural anxiety in healthy young individuals when standing quietly or performing voluntary postural tasks. However, little is known about the influence of anxiety on reactive postural control. The present study examined how increased postural anxiety influenced postural reactions to unexpected surface rotations in multiple directions. Ten healthy young adults (mean age: 25.5 yr, range: 22–27 yr) were required to recover from unexpected rotations of the support surface (7.5° amplitude, 50°/s velocity) delivered in six different directions while standing in a low postural threat (surface height: 60 cm above ground) or high postural threat (surface height: 160 cm above ground) condition. Electromyographic data from 12 different postural leg, hip, and trunk muscles was collected simultaneously. Full body kinematic data were also used to determine total body center of mass (COM) and segment displacements. Four distinct changes were observed with increased postural anxiety: increased amplitude in balance-correcting responses (120–220 ms) in all leg, trunk, and arm muscles; decreased onset latency of deltoid responses; reduced magnitude of COM displacement; and reduced angular displacement of leg, pelvis, and trunk. These observations suggest that changes in dynamic postural responses with increased anxiety are mediated by alterations in neuro-muscular control mechanisms and thus may contribute significantly to the pathophysiology of balance deficits associated with aging or neurological disease.

First Trial Postural Reactions to Unexpected Balance Disturbances: A Comparison With the Acoustic Startle Reaction

2010 ◽  
Vol 104 (5) ◽  
pp. 2704-2712 ◽  
Author(s):  
Lars B. Oude Nijhuis ◽  
John H. J. Allum ◽  
Josep Valls-Solé ◽  
Sebastiaan Overeem ◽  
Bastiaan R. Bloem
Keyword(s):  
Muscle Activation ◽  
Acoustic Startle ◽  
Muscle Synergy ◽  
Trunk Muscles ◽  
Common Element ◽  
Startle Reaction ◽  
Support Surface ◽  
Postural Reactions ◽  
Acoustic Stimuli ◽  
Postural Responses

Unexpected support-surface movements delivered during stance elicit “first trial” postural reactions, which are larger and cause greater instability compared with habituated responses. The nature of this first trial reaction remains unknown. We hypothesized that first trial postural reactions consist of a generalized startle reaction, with a similar muscle synergy as the acoustic startle response, combined with an automatic postural reaction. Therefore we compared acoustic startle responses to first trial postural reactions. Eight healthy subjects stood on a support surface that unexpectedly rotated backwards 10 times, followed by 10 startling acoustic stimuli, or vice versa. Outcome measures included full body kinematics and surface EMG from muscles involved in startle reactions or postural control. Postural perturbations and startling acoustic stimuli both elicited a clear first trial reaction, as reflected by larger kinematic and EMG responses. The ensuing habituation rate to repeated identical stimuli was comparable for neck and trunk muscles in both conditions. Onset latencies in neck muscles occurred significantly later for first trial perturbations compared with startle responses, but earlier in trunk muscles. Our results show that platform tilting initially induces reactions larger than needed to maintain equilibrium. For neck and trunk muscles, these first trial postural reactions resembled acoustic startle reflexes. First trial postural reactions may be triggered by interaction of afferent volleys formed by somatosensory and vestibular inputs. Acoustic startle reactions may also be partially triggered by vestibular inputs. Similar muscle activation driven by vestibular inputs may be the common element of first trial postural responses and acoustic startle reactions.

Bilateral labyrinthectomy in the cat: effects on the postural response to translation

1995 ◽  
Vol 73 (3) ◽  
pp. 1181-1191 ◽  
Author(s):  
J. T. Inglis ◽  
J. M. Macpherson
Keyword(s):  
Visual Information ◽  
Center Of Mass ◽  
Afferent Input ◽  
Support Surface ◽  
Postural Response ◽  
Automatic Postural Response ◽  
Somatosensory Information ◽  
Postural Responses ◽  
Before And After ◽  
Evoked Activity

1. This study examined the role of vestibular afferent information on the postural responses of four cats, evoked by movements of the support surface during stance. Animals were exposed to linear translations of the supporting surface in eight evenly spaced directions in the horizontal plane, before and after bilateral labyrinthectomy. Postural responses were quantified in terms of the ground reaction forces under each paw and the evoked activity in selected muscles. 2. The cats were able to stand on the platform within 1-3 days after labyrinthectomy and were able to maintain balance during all perturbations of stance, even when they stood in total darkness, completely deprived of visual information. After lesion, postural responses were characterized by normal latency and normal spatial and temporal patterning of electromyographic (EMG) response. The pattern of force response showed the force constraint strategy that characterizes postural responses in the intact animal. 3. The only deficit in the postural response after lesion was a hypermetria, or active over-response that caused the animals to overbalance somewhat but did not impair their ability to remain upright. Analysis of the trajectory of the animal's center of mass during the trials indicated that the hypermetria was due to an abnormally large, active response on the part of the animal and could not be attributed to changes in the passive stiffness of the musculoskeletal system. The hypermetria was transient, and response amplitude returned to control levels after the rapid compensation phase of 10-15 days. 4. It is concluded that vestibular information is not essential for triggering the rapid, automatic postural response to translations of the support surface, nor is it necessary for the selection or shaping of the evoked response. Instead, somatosensory information appears to predominate in these postural adjustments. However, vestibular afferent input does influence the scaling of the postural response.

scholarly journals Postural threat influences vestibular-evoked muscular responses

2017 ◽  
Vol 117 (2) ◽  
pp. 604-611 ◽  
Author(s):  
Shannon B. Lim ◽  
Taylor W. Cleworth ◽  
Brian C. Horslen ◽  
Jean-Sébastien Blouin ◽  
J. Timothy Inglis ◽  
...  
Keyword(s):  
Cross Correlation ◽  
Balance Control ◽  
Standing Balance ◽  
Medial Gastrocnemius ◽  
Trunk Muscles ◽  
Support Surface ◽  
Evoked Responses ◽  
Lower Body ◽  
Leg Muscles ◽  
Postural Threat

Standing balance is significantly influenced by postural threat. While this effect has been well established, the underlying mechanisms of the effect are less understood. The involvement of the vestibular system is under current debate, and recent studies that investigated the effects of height-induced postural threat on vestibular-evoked responses provide conflicting results based on kinetic (Horslen BC, Dakin CJ, Inglis JT, Blouin JS, Carpenter MG. J Physiol 592: 3671–3685, 2014) and kinematic (Osler CJ, Tersteeg MC, Reynolds RF, Loram ID. Eur J Neurosci 38: 3239–3247, 2013) data. We examined the effect of threat of perturbation, a different form of postural threat, on coupling (cross-correlation, coherence, and gain) of the vestibulo-muscular relationship in 25 participants who maintained standing balance. In the “No-Threat” conditions, participants stood quietly on a stable surface. In the “Threat” condition, participants' balance was threatened with unpredictable mediolateral support surface tilts. Quiet standing immediately before the surface tilts was compared to an equivalent time from the No-Threat conditions. Surface EMG was recorded from bilateral trunk, hip, and leg muscles. Hip and leg muscles exhibited significant increases in peak cross-correlation amplitudes, coherence, and gain (1.23–2.66×) in the Threat condition compared with No-Threat conditions, and significant correlations were observed between threat-related changes in physiological arousal and medium-latency peak cross-correlation amplitude in medial gastrocnemius ( r = 0.408) muscles. These findings show a clear threat effect on vestibular-evoked responses in muscles in the lower body, with less robust effects of threat on trunk muscles. Combined with previous work, the present results can provide insight into observed changes during balance control in threatening situations. NEW & NOTEWORTHY This is the first study to show increases in vestibular-evoked responses of the lower body muscles under conditions of increased threat of postural perturbation. While robust findings were observed in hip and leg muscles, less consistent results were found in muscles of the trunk. The present findings provide further support in the ongoing debate for arguments that vestibular-evoked balance responses are influenced by fear and anxiety and explain previous threat-related changes in balance.

Alteration of Postural Responses Due to Chronic Recurrent Low Back Pain

2004 ◽  
Author(s):  
Sharon M. Henry ◽  
Juvena R. Hitt ◽  
Stephanie L. Jones ◽  
Janice Y. Bunn
Keyword(s):  
Low Back Pain ◽  
Back Pain ◽  
Center Of Pressure ◽  
Center Of Mass ◽  
Force Plate ◽  
Support Surface ◽  
Low Back ◽  
Joint Torques ◽  
Postural Responses ◽  
Recurrent Low Back Pain

This study characterized postural responses in subjects with (n=26, 39 ± 13 yrs) and without (n=24, 32 ± 10 yrs) chronic ( >6 months), recurrent low back pain (LBP) in response to support surface translations, randomly delivered in 12 different horizontal directions. Using kinematic, force plate and anthropometric data, the net center of pressure (CP), total body center of mass (CM), and net joint torques (sagittal and frontal planes) at the ankle, knee, hip and trunk were examined to characterize the neuromuscular responses in the two subject groups. LBP subjects exhibited larger anterior and posterior CM displacements compared to NLBP (p = 0.0267) and smaller anterior and posterior CP displacements (p <0.0001). Overall, torque responses in persons with LBP were smaller, delayed and developed more quickly compared to NLBP subjects and the responses were non-directionally specific. These data suggest the automatic postural control of subjects with LBP is altered such that there is an overall stiffening strategy for LBP subjects, which is reflected in the reduced CP displacement and the smaller and delayed torque responses.

scholarly journals Common muscle synergies for control of center of mass and force in nonstepping and stepping postural behaviors

2011 ◽  
Vol 106 (2) ◽  
pp. 999-1015 ◽  
Author(s):  
Stacie A. Chvatal ◽  
Gelsy Torres-Oviedo ◽  
Seyed A. Safavynia ◽  
Lena H. Ting
Keyword(s):  
Muscle Activity ◽  
Center Of Mass ◽  
Initial Position ◽  
Neural Mechanisms ◽  
Muscle Synergies ◽  
Support Surface ◽  
Ground Reaction Forces ◽  
Postural Responses ◽  
Reaction Forces ◽  
Base Of Support

We investigated muscle activity, ground reaction forces, and center of mass (CoM) acceleration in two different postural behaviors for standing balance control in humans to determine whether common neural mechanisms are used in different postural tasks. We compared nonstepping responses, where the base of support is stationary and balance is recovered by returning CoM back to its initial position, with stepping responses, where the base of support is enlarged and balance is recovered by pushing the CoM away from the initial position. In response to perturbations of the same direction, these two postural behaviors resulted in different muscle activity and ground reaction forces. We hypothesized that a common pool of muscle synergies producing consistent task-level biomechanical functions is used to generate different postural behaviors. Two sets of support-surface translations in 12 horizontal-plane directions were presented, first to evoke stepping responses and then to evoke nonstepping responses. Electromyographs in 16 lower back and leg muscles of the stance leg were measured. Initially (∼100-ms latency), electromyographs, CoM acceleration, and forces were similar in nonstepping and stepping responses, but these diverged in later time periods (∼200 ms), when stepping occurred. We identified muscle synergies using non-negative matrix factorization and functional muscle synergies that quantified correlations between muscle synergy recruitment levels and biomechanical outputs. Functional muscle synergies that produce forces to restore CoM position in nonstepping responses were also used to displace the CoM during stepping responses. These results suggest that muscle synergies represent common neural mechanisms for CoM movement control under different dynamic conditions: stepping and nonstepping postural responses.

Effect of Stance Width on Multidirectional Postural Responses

2001 ◽  
Vol 85 (2) ◽  
pp. 559-570 ◽  
Author(s):  
Sharon M. Henry ◽  
Joyce Fung ◽  
Fay B. Horak
Keyword(s):  
Muscle Activation ◽  
Center Of Pressure ◽  
Center Of Mass ◽  
Trunk Muscles ◽  
Horizontal Force ◽  
Passive Stiffness ◽  
Tuning Curves ◽  
Equilibrium Control ◽  
Postural Responses ◽  
Static Approach

The effect of stance width on postural responses to 12 different directions of surface translations was examined. Postural responses were characterized by recording 11 lower limb and trunk muscles, body kinematics, and forces exerted under each foot of 7 healthy subjects while they were subjected to horizontal surface translations in 12 different, randomly presented directions. A quasi-static approach of force analysis was done, examining force integrals in three different epochs (background, passive, and active periods). The latency and amplitude of muscle responses were quantified for each direction, and muscle tuning curves were used to determine the spatial activation patterns for each muscle. The results demonstrate that the horizontal force constraint exerted at the ground was lessened in the wide, compared with narrow, stance for humans, a similar finding to that reported by Macpherson for cats. Despite more trunk displacement in narrow stance, there were no significant changes in body center of mass (CoM) displacement due to large changes in center of pressure (CoP), especially in response to lateral translations. Electromyographic (EMG) magnitude decreased for all directions in wide stance, particularly for the more proximal muscles, whereas latencies remained the same from narrow to wide stance. Equilibrium control in narrow stance was more of an active postural strategy that included regulating the loading/unloading of the limbs and the direction of horizontal force vectors. In wide stance, equilibrium control relied more on an increase in passive stiffness resulting from changes in limb geometry. The selective latency modulation of the proximal muscles with translation direction suggests that the trunk was being actively controlled in all directions. The similar EMG latencies for both narrow and wide stance, with modulation of only the muscle activation magnitude as stance width changed, suggest that the same postural synergy was only slightly modified for a change in stance width. Nevertheless, the magnitude of the trunk displacement, as well as of CoP displacement, was modified based on the degree of passive stiffness in the musculoskeletal system, which increased with stance width. The change from a more passive to an active horizontal force constraint, to larger EMG magnitudes especially in the trunk muscles and larger trunk and CoP excursions in narrow stance are consistent with a more effortful response for equilibrium control in narrow stance to perturbations in all directions.

scholarly journals Interactions between initial posture and task-level goal explain experimental variability in postural responses to perturbations of standing balance

2020 ◽  
Author(s):  
Tom Van Wouwe ◽  
Lena H Ting ◽  
Friedl De Groote
Keyword(s):  
Center Of Mass ◽  
Standing Balance ◽  
Support Surface ◽  
Movement Variability ◽  
Postural Responses ◽  
Subject Variability ◽  
Subject Specific ◽  
Experimental Variability ◽  
Task Level ◽  
And Task

Postural responses to similar perturbations of standing balance vary widely within and across subjects. Here, we identified two sources of variability and their interactions by combining experimental observations with computational modeling: differences in posture at perturbation onset across trials, and differences in task-level goals across subjects. We first collected postural responses to unpredictable backward support-surface translations during standing in 10 young adults. We found that maximal trunk lean in postural responses to backward translations were highly variable both within (mean of ranges 28.3°) and across subjects (range of means 39.9°). Initial center of mass (COM) position was correlated with maximal trunk lean during the response but this relation was subject specific (R² = 0.29 - 0.82). We then used predictive simulations to assess causal relations and interactions with task-level goal. Our simulations showed that initial posture explains the experimentally observed intra-subject variability with a more anterior initial COM position increasing the use of the hip strategy. Differences in task-level goal explain observed inter-subject variability with prioritizing effort minimization leading to ankle strategies and prioritizing stability leading to hip strategies. Interactions between initial posture and task-level goal explain observed differences in intra-subject variability across subjects. Our findings suggest that variability in initial posture due to increased sway as observed in older adults might increase the occurrence of less stable postural responses to perturbations. Insight in factors causing movement variability will advance our ability to study the origin of differences between groups and conditions.

First trial and StartReact effects induced by balance perturbations to upright stance

2013 ◽  
Vol 110 (9) ◽  
pp. 2236-2245 ◽  
Author(s):  
A. D. Campbell ◽  
J. W. Squair ◽  
R. Chua ◽  
J. T. Inglis ◽  
M. G. Carpenter
Keyword(s):  
Startle Response ◽  
Support Surface ◽  
Wrist Movement ◽  
Repeated Presentation ◽  
Trial Effect ◽  
Acoustic Stimuli ◽  
Postural Responses ◽  
Startreact Effect ◽  
Startling Stimulus ◽  
Repeated Test

Postural responses (PR) to a balance perturbation differ between the first and subsequent perturbations. One explanation for this first trial effect is that perturbations act as startling stimuli that initiate a generalized startle response (GSR) as well as the PR. Startling stimuli, such as startling acoustic stimuli (SAS), are known to elicit GSRs, as well as a StartReact effect, in which prepared movements are initiated earlier by a startling stimulus. In this study, a StartReact effect paradigm was used to determine if balance perturbations can also act as startle stimuli. Subjects completed two blocks of simple reaction time trials involving wrist extension to a visual imperative stimulus (IS). Each block included 15 CONTROL trials that involved a warning cue and subsequent IS, followed by 10 repeated TEST trials, where either a SAS (TESTSAS) or a toes-up support-surface rotation (TESTPERT) was presented coincident with the IS. StartReact effects were observed during the first trial in both TESTSAS and TESTPERT conditions as evidenced by significantly earlier wrist movement and muscle onsets compared with CONTROL. Likewise, StartReact effects were observed in all repeated TESTSAS and TESTPERT trials. In contrast, GSRs in sternocleidomastoid and PRs were large in the first trial, but significantly attenuated over repeated presentation of the TESTPERT trials. Results suggest that balance perturbations can act as startling stimuli. Thus first trial effects are likely PRs which are superimposed with a GSR that is initially large, but habituates over time with repeated exposure to the startling influence of the balance perturbation.

Organization of postural responses following a rotational support surface perturbation, after TKA: Sagittal plane rotations

2007 ◽  
Vol 25 (1) ◽  
pp. 112-120 ◽  
Author(s):  
William H. Gage ◽  
James S. Frank ◽  
Stephen D. Prentice ◽  
Peter Stevenson
Keyword(s):  
Sagittal Plane ◽  
Support Surface ◽  
Surface Perturbation ◽  
Postural Responses

scholarly journals Response to Tendon Vibration Questions the Underlying Rationale of Proprioceptive Training

2017 ◽  
Vol 52 (2) ◽  
pp. 97-107 ◽  
Author(s):  
Anat Vilnai Lubetzky ◽  
Sarah Westcott McCoy ◽  
Robert Price ◽  
Deborah Kartin
Keyword(s):  
Achilles Tendon ◽  
Center Of Pressure ◽  
Multiscale Entropy ◽  
Support Surface ◽  
Ankle Sprains ◽  
Control Mechanisms ◽  
Tendon Vibration ◽  
Healthy Group ◽  
Proprioceptive Training ◽  
Proprioceptive Function

Context: Proprioceptive training on compliant surfaces is used to rehabilitate and prevent ankle sprains. The ability to improve proprioceptive function via such training has been questioned. Achilles tendon vibration is used in motor-control research as a form of proprioceptive stimulus. Using measures of postural steadiness with nonlinear measures to elucidate control mechanisms, tendon vibration can be applied to investigate the underlying rationale of proprioceptive training. Objective: To test whether the effect of vibration on young adults' postural control depended on the support surface. Design: Descriptive laboratory study. Setting: Research laboratory. Patients or Other Participants: Thirty healthy adults and 10 adults with chronic ankle instability (CAI; age range = 18−40 years). Intervention(s): With eyes open, participants stood in bilateral stance on a rigid plate (floor), memory foam, and a Both Sides Up (BOSU) ball covering a force platform. We applied bilateral Achilles tendon vibration for the middle 20 seconds in a series of 60-second trials and analyzed participants' responses from previbration to vibration (pre-vib) and from vibration to postvibration (vib-post). Main Outcome Measure(s): We calculated anterior-posterior excursion of the center of pressure and complexity index derived from the area under multiscale entropy curves. Results: The excursion response to vibration differed by surface, as indicated by a significant interaction of P < .001 for the healthy group at both time points and for the CAI group vib-post. Although both groups demonstrated increased excursion from pre-vib and from vib-post, a decrease was observed on the BOSU. The complexity response to vibration differed by surface for the healthy group (pre-vib, P < .001). The pattern for the CAI group was similar but not significant. Complexity changes vib-post were the same on all surfaces for both groups. Conclusions: Participants reacted less to ankle vibration when standing on the BOSU as compared with the floor, suggesting that proprioceptive training may not be occurring. Different balance-training paradigms to target proprioception, including tendon vibration, should be explored.

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