Paradoxical Muscle Movement during Postural Control

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Paradoxical Muscle Movement during Postural Control. / Loram, ID; Maganaris, CN; Lakie, Martin.

In: Medicine and Science in Sports and Exercise, Vol. 41, No. 1, 01.01.2009, p. 198-204.

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@article{62d5f253533140a09230275e551a3287,
title = "Paradoxical Muscle Movement during Postural Control",
abstract = "LORAM, I. D.,C. N. MAGANARIS, and M. LAKIE. Paradoxical Muscle Movement during Postural Control. Med. Sci. Sports Exerc., Vol. 41, No. 1, pp. 198-204, 2009. Undisturbed human standing is primarily characterized by sway of the whole body about the ankle joints and is regulated primarily by the calf muscles. Traditionally, in accord with normal ideas of postural control, ankle stiffness, enhanced by spindle mediated muscle stretch reflexes, has been considered to be important for maintaining the upright human stance. This idea predicts that during forward sway, the calf muscles are stretched and the mechanoreflex response enhances muscle activity to maintain posture and balance. Muscle contractile displacement is expected to be positively correlated with bodily sway. However, recent experiments have revealed problems with these ideas. Using a new ultrasound technique for viewing and measuring the dynamic contractile displacements of the calf muscles, it has been shown that calf muscle movement is usually poorly or negatively correlated with bodily sway. The shortening of the contractile tissue during forward sway and vice versa is described as paradoxical muscle movements. This paradoxical muscle movement can be explained by the fact that the Achilles tendon, which transmits the calf muscle force, is compliant in relation the bodily load. There are two main consequences of the compliant Achilles tendon. First, the body is unstable: it cannot be stabilized by intrinsic ankle stiffness alone and thus requires modulation of muscle activity to maintain balance. Second, contractile displacement is mechanically decoupled from bodily sway, which implies that stretch-reflex mechanisms mediated by the calf muscle spindles are unable to successfully modulate muscle activity to maintain balance. This leaves uncertain the postural role of the numerous calf muscle spindles: it is predicted that they signal the effective motor output rather than bodily sway.",
keywords = "STRETCH REFLEX, SOLEUS, ULTRASONAGRAPHY, HUMAN STANDING, POSTURE, GASTROCNEMIUS",
author = "ID Loram and CN Maganaris and Martin Lakie",
year = "2009",
month = jan,
day = "1",
doi = "10.1249/MSS.0b013e318183c0ed",
language = "English",
volume = "41",
pages = "198--204",
journal = "Medicine and Science in Sports and Exercise",
issn = "0195-9131",
publisher = "American College of Sports Medicine",
number = "1",

}

RIS

TY - JOUR

T1 - Paradoxical Muscle Movement during Postural Control

AU - Loram, ID

AU - Maganaris, CN

AU - Lakie, Martin

PY - 2009/1/1

Y1 - 2009/1/1

N2 - LORAM, I. D.,C. N. MAGANARIS, and M. LAKIE. Paradoxical Muscle Movement during Postural Control. Med. Sci. Sports Exerc., Vol. 41, No. 1, pp. 198-204, 2009. Undisturbed human standing is primarily characterized by sway of the whole body about the ankle joints and is regulated primarily by the calf muscles. Traditionally, in accord with normal ideas of postural control, ankle stiffness, enhanced by spindle mediated muscle stretch reflexes, has been considered to be important for maintaining the upright human stance. This idea predicts that during forward sway, the calf muscles are stretched and the mechanoreflex response enhances muscle activity to maintain posture and balance. Muscle contractile displacement is expected to be positively correlated with bodily sway. However, recent experiments have revealed problems with these ideas. Using a new ultrasound technique for viewing and measuring the dynamic contractile displacements of the calf muscles, it has been shown that calf muscle movement is usually poorly or negatively correlated with bodily sway. The shortening of the contractile tissue during forward sway and vice versa is described as paradoxical muscle movements. This paradoxical muscle movement can be explained by the fact that the Achilles tendon, which transmits the calf muscle force, is compliant in relation the bodily load. There are two main consequences of the compliant Achilles tendon. First, the body is unstable: it cannot be stabilized by intrinsic ankle stiffness alone and thus requires modulation of muscle activity to maintain balance. Second, contractile displacement is mechanically decoupled from bodily sway, which implies that stretch-reflex mechanisms mediated by the calf muscle spindles are unable to successfully modulate muscle activity to maintain balance. This leaves uncertain the postural role of the numerous calf muscle spindles: it is predicted that they signal the effective motor output rather than bodily sway.

AB - LORAM, I. D.,C. N. MAGANARIS, and M. LAKIE. Paradoxical Muscle Movement during Postural Control. Med. Sci. Sports Exerc., Vol. 41, No. 1, pp. 198-204, 2009. Undisturbed human standing is primarily characterized by sway of the whole body about the ankle joints and is regulated primarily by the calf muscles. Traditionally, in accord with normal ideas of postural control, ankle stiffness, enhanced by spindle mediated muscle stretch reflexes, has been considered to be important for maintaining the upright human stance. This idea predicts that during forward sway, the calf muscles are stretched and the mechanoreflex response enhances muscle activity to maintain posture and balance. Muscle contractile displacement is expected to be positively correlated with bodily sway. However, recent experiments have revealed problems with these ideas. Using a new ultrasound technique for viewing and measuring the dynamic contractile displacements of the calf muscles, it has been shown that calf muscle movement is usually poorly or negatively correlated with bodily sway. The shortening of the contractile tissue during forward sway and vice versa is described as paradoxical muscle movements. This paradoxical muscle movement can be explained by the fact that the Achilles tendon, which transmits the calf muscle force, is compliant in relation the bodily load. There are two main consequences of the compliant Achilles tendon. First, the body is unstable: it cannot be stabilized by intrinsic ankle stiffness alone and thus requires modulation of muscle activity to maintain balance. Second, contractile displacement is mechanically decoupled from bodily sway, which implies that stretch-reflex mechanisms mediated by the calf muscle spindles are unable to successfully modulate muscle activity to maintain balance. This leaves uncertain the postural role of the numerous calf muscle spindles: it is predicted that they signal the effective motor output rather than bodily sway.

KW - STRETCH REFLEX

KW - SOLEUS

KW - ULTRASONAGRAPHY

KW - HUMAN STANDING

KW - POSTURE

KW - GASTROCNEMIUS

U2 - 10.1249/MSS.0b013e318183c0ed

DO - 10.1249/MSS.0b013e318183c0ed

M3 - Article

C2 - 19092688

VL - 41

SP - 198

EP - 204

JO - Medicine and Science in Sports and Exercise

JF - Medicine and Science in Sports and Exercise

SN - 0195-9131

IS - 1

ER -