Intrinsic ankle stiffness during standing increases with ankle torque and passive stretch of the Achilles tendon.
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 apone...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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Public Library of Science (PLoS)
2018-01-01
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| Series: | PLoS ONE |
| Online Access: | http://europepmc.org/articles/PMC5860743?pdf=render |
| _version_ | 1819141896641970176 |
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| author | Tania E Sakanaka Jaspret Gill Martin D Lakie Raymond F Reynolds |
| author_facet | Tania E Sakanaka Jaspret Gill Martin D Lakie Raymond F Reynolds |
| author_sort | Tania E Sakanaka |
| collection | DOAJ |
| description | 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. |
| first_indexed | 2024-12-22T12:01:44Z |
| format | Article |
| id | doaj.art-7889129765e14974b0c5f0d22ff84ee8 |
| institution | Directory Open Access Journal |
| issn | 1932-6203 |
| language | English |
| last_indexed | 2024-12-22T12:01:44Z |
| publishDate | 2018-01-01 |
| publisher | Public Library of Science (PLoS) |
| record_format | Article |
| series | PLoS ONE |
| spelling | doaj.art-7889129765e14974b0c5f0d22ff84ee82022-12-21T18:26:34ZengPublic Library of Science (PLoS)PLoS ONE1932-62032018-01-01133e019385010.1371/journal.pone.0193850Intrinsic ankle stiffness during standing increases with ankle torque and passive stretch of the Achilles tendon.Tania E SakanakaJaspret GillMartin D LakieRaymond F ReynoldsIndividuals 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.http://europepmc.org/articles/PMC5860743?pdf=render |
| spellingShingle | Tania E Sakanaka Jaspret Gill Martin D Lakie Raymond F Reynolds Intrinsic ankle stiffness during standing increases with ankle torque and passive stretch of the Achilles tendon. PLoS ONE |
| title | Intrinsic ankle stiffness during standing increases with ankle torque and passive stretch of the Achilles tendon. |
| title_full | Intrinsic ankle stiffness during standing increases with ankle torque and passive stretch of the Achilles tendon. |
| title_fullStr | Intrinsic ankle stiffness during standing increases with ankle torque and passive stretch of the Achilles tendon. |
| title_full_unstemmed | Intrinsic ankle stiffness during standing increases with ankle torque and passive stretch of the Achilles tendon. |
| title_short | Intrinsic ankle stiffness during standing increases with ankle torque and passive stretch of the Achilles tendon. |
| title_sort | intrinsic ankle stiffness during standing increases with ankle torque and passive stretch of the achilles tendon |
| url | http://europepmc.org/articles/PMC5860743?pdf=render |
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