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.

scholarly journals Vestibular contribution to balance control in the medial gastrocnemius and soleus

2016 ◽  
Vol 115 (3) ◽  
pp. 1289-1297 ◽  
Author(s):  
Christopher J. Dakin ◽  
Martin E. Héroux ◽  
Billy L. Luu ◽  
John Timothy Inglis ◽  
Jean-Sébastien Blouin
Keyword(s):  
Surface Electromyography ◽  
Balance Control ◽  
Motor Units ◽  
Vestibular Stimulation ◽  
Standing Balance ◽  
Medial Gastrocnemius ◽  
Functional Roles ◽  
Discharge Behavior ◽  
Balance Corrections ◽  
Biphasic Responses

The soleus (Sol) and medial gastrocnemius (mGas) muscles have different patterns of activity during standing balance and may have distinct functional roles. Using surface electromyography we previously observed larger responses to galvanic vestibular stimulation (GVS) in the mGas compared with the Sol muscle. However, it is unclear whether this difference is an artifact that reflects limitations associated with surface electromyography recordings or whether a compensatory balance response to a vestibular error signal activates the mGas to a greater extent than the Sol. In the present study, we compared the effect of GVS on the discharge behavior of 9 Sol and 21 mGas motor units from freely standing subjects. In both Sol and mGas motor units, vestibular stimulation induced biphasic responses in measures of discharge timing [11 ± 5.0 (mGas) and 5.6 ± 3.8 (Sol) counts relative to the sham (mean ± SD)], and frequency [0.86 ± 0.6 Hz (mGas), 0.34 ± 0.2 Hz (Sol) change relative to the sham]. Peak-to-trough response amplitudes were significantly larger in the mGas (62% in the probability-based measure and 160% in the frequency-based measure) compared with the Sol (multiple P < 0.05). Our results provide direct evidence that vestibular signals have a larger influence on the discharge activity of motor units in the mGas compared with the Sol. More tentatively, these results indicate the mGas plays a greater role in vestibular-driven balance corrections during standing balance.

scholarly journals Influence of Stance Width on Frontal Plane Postural Dynamics and Coordination in Human Balance Control

2010 ◽  
Vol 104 (2) ◽  
pp. 1103-1118 ◽  
Author(s):  
Adam D. Goodworth ◽  
Robert J. Peterka
Keyword(s):  
Frequency Response ◽  
Balance Control ◽  
Frontal Plane ◽  
Body Motion ◽  
Upper Body ◽  
Body Sway ◽  
Support Surface ◽  
Lower Body ◽  
Stimulus Amplitude ◽  
Postural System

The influence of stance width on frontal plane postural dynamics and coordination in human bipedal stance was studied. We tested the hypothesis that when subjects adopt a narrow stance width, they will rely heavily on nonlinear control strategies and coordinated counter-phase upper and lower body motion to limit center-of-mass (CoM) deviations from upright; as stance increases, the use of these strategies will diminish. Freestanding frontal plane body sway was evoked through continuous pseudorandom rotations of the support surface on which subjects stood with various stimulus amplitudes. Subjects were either eyes open (EO) or closed (EC) and adopted various stance widths. Upper body, lower body, and CoM kinematics were summarized using root-mean-square and peak-to-peak measures, and dynamic behavior was characterized using frequency-response and impulse-response functions. In narrow stance, CoM frequency-response function gains were reduced with increasing stimulus amplitude and in EO compared with EC; in wide stance, gain reductions were much less pronounced. Results show that the narrow stance postural system is nonlinear across stimulus amplitude in both EO and EC conditions, whereas the wide stance postural system is more linear. The nonlinearity in narrow stance is likely caused by an amplitude-dependent sensory reweighting mechanism. Finally, lower body and upper body sway were approximately in-phase at low frequencies (<1 Hz) and out-of-phase at high frequencies (>1 Hz) across all stance widths, and results were therefore inconsistent with the hypothesis that subjects made greater use of coordinated counter-phase upper and lower body motion in narrow compared with wide stance conditions.

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.

scholarly journals Intermittent short-arm centrifugation is a partially effective countermeasure against upright balance deterioration following 60-day head-down tilt bed rest

2021 ◽  
Author(s):  
Enrico De Martino ◽  
Sauro Emerick Salomoni ◽  
Paul W. Hodges ◽  
Julie Hides ◽  
Kirsty Lindsay ◽  
...  
Keyword(s):  
Bed Rest ◽  
Standing Balance ◽  
Erector Spinae ◽  
Transversus Abdominis ◽  
Trunk Muscles ◽  
Control Group ◽  
Protective Effects ◽  
Gravitational Unloading ◽  
Frequency Power ◽  
Sway Frequency

This study investigated whether artificial gravity (AG), induced by short-radius centrifugation, mitigated deterioration in standing balance and anticipatory postural adjustments (APAs) of trunk muscles following 60-day head-down tilt bed rest. Twenty-four participants were allocated to one of three groups: control group (N=8); 30 minutes continuous AG daily (N=8); intermittent 6x5 minutes AG daily (N=8). Before and immediately after bed rest, standing balance was assessed in four conditions: eyes open and closed on both stable and foam surfaces. Measures including sway path, root-mean-square, and peak sway velocity, sway area, sway frequency power, and sway density curve were extracted from the centre of pressure displacement. APAs were assessed during rapid arm movements using intramuscular or surface electromyography electrodes of the rectus abdominis, obliquus externus and internus abdominis, transversus abdominis, erector spinae at L1, L2, L3, and L4 vertebral levels, and deep lumbar multifidus muscles. The relative latency between the EMG onset of the deltoid and each of the trunk muscles was calculated. All three groups had poorer balance performance in most of the parameters (all P<0.05) and delayed APAs of the trunk muscles following bed rest (all P<0.05). Sway path and sway velocity were deteriorated, and sway frequency power was less in those who received intermittent AG than in the control group (all P<0.05), particularly in conditions with reduced proprioceptive feedback. These data highlight the potential of intermittent AG to mitigate deterioration of some aspects of postural control induced by gravitational unloading, but no protective effects on trunk muscle responses were observed.

An overview of the clinical use of dynamic posturography in the differential diagnosis of balance disorders

1999 ◽  
Vol 9 (4) ◽  
pp. 223-252
Author(s):  
John H.J. Allum ◽  
Neil T. Shepard
Keyword(s):  
Differential Diagnosis ◽  
Functional Disability ◽  
Balance Control ◽  
Test Subject ◽  
Motor Deficits ◽  
Support Surface ◽  
Dynamic Posturography ◽  
Balance Disorders ◽  
Balance Disorder ◽  
Proprioceptive Reflex

Dynamic posturography comprises a series of balance control tests which help physicians overcome numerous diagnostic and treatment challenges arising when examining patients complaining of a debilitating balance disorder. These challenges include the specific differential diagnosis, documentation of symptoms and assessment of functional disability. It must be determined whether the cause of the disability is an organic sensory deficit, a central nervous system (CNS) lesion or a non-organic (that is, possibly psychogenic or just overtly simulated) disorder. This review is targeted towards providing the reader (a) an overview of the effects sensori-motor deficits have on balance control, specifically vestibulo-spinal and proprioceptive reflex deficits; and, (b) how these effects may be assessed objectively in a clinical setting to differentiate between various organic and non-organic balance-disorders. The techniques used to study these effects are based on the analysis of both rapid balance-correcting and slow balance-stabilizing responses to fast and slow movements in the pitch plane of the support surface on which the test subject stands.

scholarly journals The Importance of Lean Body Mass for the Rate of Force Development in Taekwondo Athletes and Track and Field Throwers

2018 ◽  
Vol 3 (3) ◽  
pp. 43 ◽  
Author(s):  
Angeliki Kavvoura ◽  
Nikolaos Zaras ◽  
Angeliki-Nikoletta Stasinaki ◽  
Giannis Arnaoutis ◽  
Spyridon Methenitis ◽  
...  
Keyword(s):  
Lean Body Mass ◽  
Body Mass ◽  
Vastus Lateralis ◽  
Rate Of Force Development ◽  
Track And Field ◽  
Medial Gastrocnemius ◽  
Lower Body ◽  
Leg Extension ◽  
Force Development ◽  
The Relationship

The rate of force development (RFD) is vital for power athletes. Lean body mass (LBM) is considered to be an essential contributor to RFD, nevertheless high RFD may be achieved by athletes with either high or low LBM. The aim of the study was to describe the relationship between lower-body LBM and RFD, and to compare RFD in taekwondo athletes and track and field (T&F) throwers, the latter having higher LBM when compared to taekwondo athletes. Nine taekwondo athletes and nine T&F throwers were evaluated for countermovement jumping, isometric leg press and leg extension RFD, vastus lateralis (VL), and medial gastrocnemius muscle architecture and body composition. Lower body LBM was correlated with RFD 0–250 ms (r = 0.81, p = 0.016). Taekwondo athletes had lower LBM and jumping power per LBM. RFD was similar between groups at 30–50 ms, but higher for throwers at 80–250 ms. RFD adjusted for VL thickness was higher in taekwondo athletes at 30 ms, but higher in throwers at 200–250 ms. These results suggest that lower body LBM is correlated with RFD in power trained athletes. RFD adjusted for VL thickness might be more relevant to evaluate in power athletes with low LBM, while late RFD might be more relevant to evaluate in athletes with higher LBM.

scholarly journals Absence of lateral gastrocnemius activity and differential motor unit behavior in soleus and medial gastrocnemius during standing balance

2014 ◽  
Vol 116 (2) ◽  
pp. 140-148 ◽  
Author(s):  
Martin E. Héroux ◽  
Christopher J. Dakin ◽  
Billy L. Luu ◽  
John Timothy Inglis ◽  
Jean-Sébastien Blouin
Keyword(s):  
Firing Rate ◽  
Motor Unit ◽  
Standing Position ◽  
Standing Balance ◽  
Triceps Surae ◽  
Medial Gastrocnemius ◽  
Isometric Contractions ◽  
Functional Requirements ◽  
Vertical Projection ◽  
Lateral Gastrocnemius

In a standing position, the vertical projection of the center of mass passes in front of the ankle, which requires active plantar-flexor torque from the triceps surae to maintain balance. We recorded motor unit (MU) activity in the medial (MG) and lateral (LG) gastrocnemius muscle and the soleus (SOL) in standing balance and voluntary isometric contractions to understand the effect of functional requirements and descending drive from different neural sources on motoneuron behavior. Single MU activity was recorded in seven subjects with wire electrodes in the triceps surae. Two 3-min standing balance trials and several ramp-and-hold contractions were performed. Lateral gastrocnemius MU activity was rarely observed in standing. The lowest thresholds for LG MUs in ramp contractions were 20–35 times higher than SOL and MG MUs ( P < 0.001). Compared with MUs from the SOL, MG MUs were intermittently active ( P < 0.001), had higher recruitment thresholds ( P = 0.022), and greater firing rate variability ( P < 0.001); this difference in firing rate variability was present in standing balance and isometric contractions. In SOL and MG MUs, both recruitment of new MUs ( R2 = 0.59–0.79, P < 0.01) and MU firing rates ( R2 = 0.05–0.40, P < 0.05) were associated with anterior-posterior and medio-lateral torque in standing. Our results suggest that the two heads of the gastrocnemius may operate in different ankle ranges with the larger MG being of primary importance when standing, likely due to its fascicle orientation. These differences in MU discharge behavior were independent of the type of descending neural drive, which points to a muscle-specific optimization of triceps surae motoneurons.

Lower Limb Human Muscle Enhancer

2001 ◽  
Author(s):  
Joseph J. Misuraca ◽  
Constantinos Mavroidis
Keyword(s):  
Lower Limb ◽  
Weight Bearing ◽  
Kinematic Chain ◽  
Human Muscle ◽  
The Body ◽  
Knee Joints ◽  
Lower Body ◽  
Loop Control ◽  
Test Fixture ◽  
Leg Muscles

Abstract This paper describes the design, control, and testing of a Human Muscle Enhancer (HME) system that will augment the muscle capabilities of subjects requiring partial lower-limb weight-bearing gait support. The HME described in this paper is a pneumatically actuated quick connecting exoskeleton system that attaches to the foot and hip area of the body, thus “closing” the lower body kinematic chain. Control of the system is achieved by using encoders at the knee joints and Myo-Pneumatic (MP) Sensors implanted into the shoes and outer garments of the human. To test this design concept, a lower body exoskeleton test fixture has been fabricated. The test fixture mimics the human leg with the top cylinder providing the body weight on the leg. Another cylinder acts as leg muscles to provide the adjustable human reaction of the leg. Preliminary open and closed loop control tests have been performed that demonstate the capability of controlling the HME using the MP sensors.

scholarly journals Dynamical Analysis of Standing Balance Control on Sloped Surfaces in Individuals with Lumbar Disc Herniation

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Jinping Li ◽  
Yang Zhang ◽  
Shasha Song ◽  
Ying Hou ◽  
Yigen Hong ◽  
...  
Keyword(s):  
Lumbar Disc Herniation ◽  
Disc Herniation ◽  
Balance Control ◽  
Lumbar Disc ◽  
Standing Balance ◽  
Dynamical Analysis
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