Intrinsic ankle stiffness during standing increases with ankle torque and passive stretch of the Achilles tendon

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Intrinsic ankle stiffness during standing increases with ankle torque and passive stretch of the Achilles tendon. / Sakanaka, Tania; Gill, Jaspret; Lakie, Martin; Reynolds, Raymond.

In: PLoS ONE, Vol. 13, No. 3, e0193850, 20.03.2018.

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@article{37512c5f1fbf44f59a83846b0692f6ae,
title = "Intrinsic ankle stiffness during standing increases with ankle torque and passive stretch of the Achilles tendon",
abstract = "Individuals may stand with a range of ankle angles. Furthermore, shoes or floor surfaces may elevate or depress their heels. Here we ask how these situations impact ankle stiffness and balance. We performed two studies (each with 10 participants) in which the triceps surae, Achilles tendon and aponeurosis were stretched either passively, by rotating the support surface, or actively by leaning forward. Participants stood freely on footplates which could rotate around the ankle joint axis. Brief, small stiffness-measuring perturbations (<0.7 deg; 140 ms) were applied at intervals of 4-5 s. In study 1, participants stood at selected angles of forward lean. In study 2, normal standing was compared with passive dorsiflexion induced by 15 deg toes-up tilt of the support surface. Smaller perturbations produced higher stiffness estimates, but for all perturbation sizes stiffness increased with active torque or passive stretch. Sway was minimally affected by stretch or lean, suggesting that this did not underlie the alterations in stiffness. In quiet stance, maximum ankle stiffness is limited by the tendon. As tendon strain increases, it becomes stiffer, causing an increase in overall ankle stiffness, which would explain the effects of leaning. However, stiffness also increased considerably with passive stretch,despite a modest torque increase. We discuss possible explanations for this increase.",
keywords = "balance , ankle stiffness , sway , achilles tendon , standing , joint torque , muscle stretch",
author = "Tania Sakanaka and Jaspret Gill and Martin Lakie and Raymond Reynolds",
year = "2018",
month = mar,
day = "20",
doi = "10.1371/journal.pone.0193850",
language = "English",
volume = "13",
journal = "PLoSONE",
issn = "1932-6203",
publisher = "Public Library of Science (PLOS)",
number = "3",

}

RIS

TY - JOUR

T1 - Intrinsic ankle stiffness during standing increases with ankle torque and passive stretch of the Achilles tendon

AU - Sakanaka, Tania

AU - Gill, Jaspret

AU - Lakie, Martin

AU - Reynolds, Raymond

PY - 2018/3/20

Y1 - 2018/3/20

N2 - Individuals may stand with a range of ankle angles. Furthermore, shoes or floor surfaces may elevate or depress their heels. Here we ask how these situations impact ankle stiffness and balance. We performed two studies (each with 10 participants) in which the triceps surae, Achilles tendon and aponeurosis were stretched either passively, by rotating the support surface, or actively by leaning forward. Participants stood freely on footplates which could rotate around the ankle joint axis. Brief, small stiffness-measuring perturbations (<0.7 deg; 140 ms) were applied at intervals of 4-5 s. In study 1, participants stood at selected angles of forward lean. In study 2, normal standing was compared with passive dorsiflexion induced by 15 deg toes-up tilt of the support surface. Smaller perturbations produced higher stiffness estimates, but for all perturbation sizes stiffness increased with active torque or passive stretch. Sway was minimally affected by stretch or lean, suggesting that this did not underlie the alterations in stiffness. In quiet stance, maximum ankle stiffness is limited by the tendon. As tendon strain increases, it becomes stiffer, causing an increase in overall ankle stiffness, which would explain the effects of leaning. However, stiffness also increased considerably with passive stretch,despite a modest torque increase. We discuss possible explanations for this increase.

AB - Individuals may stand with a range of ankle angles. Furthermore, shoes or floor surfaces may elevate or depress their heels. Here we ask how these situations impact ankle stiffness and balance. We performed two studies (each with 10 participants) in which the triceps surae, Achilles tendon and aponeurosis were stretched either passively, by rotating the support surface, or actively by leaning forward. Participants stood freely on footplates which could rotate around the ankle joint axis. Brief, small stiffness-measuring perturbations (<0.7 deg; 140 ms) were applied at intervals of 4-5 s. In study 1, participants stood at selected angles of forward lean. In study 2, normal standing was compared with passive dorsiflexion induced by 15 deg toes-up tilt of the support surface. Smaller perturbations produced higher stiffness estimates, but for all perturbation sizes stiffness increased with active torque or passive stretch. Sway was minimally affected by stretch or lean, suggesting that this did not underlie the alterations in stiffness. In quiet stance, maximum ankle stiffness is limited by the tendon. As tendon strain increases, it becomes stiffer, causing an increase in overall ankle stiffness, which would explain the effects of leaning. However, stiffness also increased considerably with passive stretch,despite a modest torque increase. We discuss possible explanations for this increase.

KW - balance

KW - ankle stiffness

KW - sway

KW - achilles tendon

KW - standing

KW - joint torque

KW - muscle stretch

U2 - 10.1371/journal.pone.0193850

DO - 10.1371/journal.pone.0193850

M3 - Article

VL - 13

JO - PLoSONE

JF - PLoSONE

SN - 1932-6203

IS - 3

M1 - e0193850

ER -