Human postural sway results from frequent, ballistic bias impulses by soleus and gastrocnemius

Loram, Ian D.; Maganaris, Constantinos N.; Lakie, Martin

doi:10.1113/jphysiol.2004.076307

Cited by 282 publications

(299 citation statements)

References 53 publications

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“…This observation partly coincides with results by Loram et al, showing that changes in the gastrocnemius EMG activity only partially correspond to the observed movements of the body center of mass (CoM) (Loram et al 2005). However, further research is needed to investigate the respective roles of the tibialis anterior and gastrocnemius muscles in human postural control.…”

Section: Effect Of Foam Support Surface and Emg Responsessupporting

confidence: 88%

Changes in multi-segmented body movements and EMG activity while standing on firm and foam support surfaces

et al. 2007

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Postural control ensures stability during both static posture and locomotion by initiating corrective adjustments in body movement. This is particularly important when the conditions of the support surface change. We investigated the effects of standing on a compliant foam surface using twelve normal subjects (mean age 26 years) in terms of: linear movements at the head, shoulder, hip and knee; EMG activity of the tibialis anterior and gastrocnemius muscles and torques towards the support surface. As subjects repeated the trials with eyes open or closed, we were also able to determine the effects of vision on multi-segmented body movements during standing upon different support surface conditions.As expected, EMG activity, torque variance values and body movements at all measured positions increased significantly when standing on foam compared with the firm surface.Linear knee and hip movements increased more, relative to shoulder and head movements while standing on foam. Vision stabilized the head and shoulder movements more than hip and knee movements while standing on foam support surface. Moreover, vision significantly reduced the tibialis anterior EMG activity and torque variance during the trials involving foam.In conclusion, the foam support surface increased corrective muscle and torque activity, and changed the firm-surface multi-segmented body movement pattern. Vision improved the ability of postural control to handle compliant surface conditions. Several essential features of postural control have been found from recording movement from multiple points on the body, synchronized with recording torque and EMG.

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Section: Effect Of Foam Support Surface and Emg Responsessupporting

confidence: 88%

Changes in multi-segmented body movements and EMG activity while standing on firm and foam support surfaces

et al. 2007

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“…Electromyography studies revealed changes in the ankle joint during quiet standing [8,11], gait and running [12,13]. These are important findings since standing sway is highly correlated with ankle joint rotation, as muscles crossing this joint are able to provide the sensory information required to maintain upright standing [14,15].…”

Section: Introductionmentioning

confidence: 94%

Influence of long-term wearing of unstable shoes on compensatory control of posture: An electromyography-based analysis

et al. 2014

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Purpose: This study investigated the influence of long-term wearing of unstable shoes (WUS) on compensatory postural adjustments (CPA) to an external perturbation.Methods: Participants were divided into two groups: one wore unstable shoes while the other wore conventional shoes for 8 weeks. The ground reaction force signal was used to calculate the anterior-posterior (AP) displacement of the centre of pressure (CoP) and the electromyographic signal of gastrocnemius medialis (GM), tibialis anterior (TA), rectus femoris (RF) and biceps femoris (BF) muscles was used to assess individual muscle activity, antagonist co-activation and reciprocal activation at the joint (TA/GM and RF/(BF+GM) pairs) and muscle group levels (ventral (TA+RF)/dorsal (GM+BF) pair) within time intervals typical for CPA. The electromyographic signal was also used to assess muscle latency. The variables described were evaluated before and after the 8-week period while wearing the unstable shoes and barefoot. Results: Long-term WUS led to: an increase of BF activity in both conditions (barefoot and wearing the unstable shoes); a decrease of GM activity; an increase of antagonist co-activation and a decrease of reciprocal activation level at the TA/GM and ventral/dorsal pairs in the unstable shoe condition. Additionally, WUS led to a decrease in CoP displacement. However, no differences were observed in muscle onset and offset. Conclusion: Results suggest that the prolonged use of unstable shoes leads to increased ankle and muscle groups' antagonist co-activation levels and higher performance by the postural control system.

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“…Using ultrasound it is possible to non-invasively measure small fluctuations in the changes in length of individual muscle fibers in the calf muscles of a person quietly standing with eyes closed [54,55]. The changes in length reflect changes in the corrective forces made to maintain balance.…”

Section: Introductionmentioning

confidence: 99%

Human Balance Control: Dead Zones, Intermittency, and Micro-chaos

Milton

Insperger

Stépàn

2015

Mathematical Approaches to Biological Systems

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Summary. The development of strategies to minimize the risk of falling in the elderly represents a major challenge for aging, in industrialized societies. The corrective movements made by humans to maintain balance are small amplitude, intermittent and ballistic. Small amplitude, complex oscillations (micro-chaos) frequently arise in industrial settings when a time-delayed digital processor attempts to stabilize an unstable equilibrium. Taken together these observations motivate considerations of the effects of a sensory threshold on the stabilization of an inverted pendulum by time-delayed feedback. In the resulting switching-type delay differential equations, the sensory threshold is a strong small-scale nonlinearity which has no effect on large-scale stabilization, but may produce complex, small amplitude dynamics including limit cycle oscillations and micro-chaos. A close mathematical relationship exists between a scalar model for balance control and the micro-chaotic map that arises in some models of digitally controlled machines. Surprisingly, transient, timedependent, bounded solutions (transient stabilization) can arise even for parameter ranges where the equilibrium is asymptotically unstable. In other words the combination of a sensory threshold with a time-delayed sampled feedback can increase the range of parameter values for which balance can be maintained, at least transiently. Neuro-biological observations suggest that sensory thresholds can be manipulated either passively by changing posture or actively using efferent feedback. Thus it may be possible to minimize the risk of falling by means of strategies that manipulate sensory thresholds by using physiotherapy and appropriate exercises.

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Human postural sway results from frequent, ballistic bias impulses by soleus and gastrocnemius

Cited by 282 publications

References 53 publications

Changes in multi-segmented body movements and EMG activity while standing on firm and foam support surfaces

Changes in multi-segmented body movements and EMG activity while standing on firm and foam support surfaces

Influence of long-term wearing of unstable shoes on compensatory control of posture: An electromyography-based analysis

Human Balance Control: Dead Zones, Intermittency, and Micro-chaos

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