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Muscle architectural properties indicate a primary role in support for the pelvic limb of three‐toed sloths (Bradypus variegatus)
Tree sloths evolved below‐branch locomotion making them one of few mammalian taxa beyond primates for which suspension is nearly obligatory. Suspension requires strong limb flexor muscles that provide both propulsion and braking/support, and available locomotor kinetics data indicate that these role...
Autores principales: | , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
John Wiley and Sons Inc.
2023
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10439369/ https://www.ncbi.nlm.nih.gov/pubmed/37190673 http://dx.doi.org/10.1111/joa.13884 |
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author | Morgan, D. M. Spainhower, K. B. Mossor, A. M. Avey‐Arroyo, J. A. Butcher, M. T. |
author_facet | Morgan, D. M. Spainhower, K. B. Mossor, A. M. Avey‐Arroyo, J. A. Butcher, M. T. |
author_sort | Morgan, D. M. |
collection | PubMed |
description | Tree sloths evolved below‐branch locomotion making them one of few mammalian taxa beyond primates for which suspension is nearly obligatory. Suspension requires strong limb flexor muscles that provide both propulsion and braking/support, and available locomotor kinetics data indicate that these roles differ between fore‐ and hindlimb pairs. Muscle structure in the pelvic limb is hypothesized to be a key anatomical correlate of function in braking/support during suspensory walking and propulsion and/or support during vertical climbing. This expectation was tested by quantifying architecture properties in the hindlimb limb musculature of brown‐throated three‐toed sloths (Bradypus variegatus: N = 7) to distinguish the roles of the flexor/extensor functional muscle groups at each joint. Measurements of muscle moment arm (r (m)), mass, belly length, fascicle length, pennation angle, and physiological cross‐sectional area (PCSA) were taken from n = 45 muscles. Overall, most muscles studied show properties for contractile excursion and fast joint rotational velocity. However, the flexor musculature is more massive (p = 0.048) and has larger PCSA (p = 0.003) than the extensors, especially at the knee joint and digits where well‐developed and strong flexors are capable of applying large joint torque. Moreover, selected hip flexors/extensors and knee flexors have modified long r (m) that can amplify applied joint torque in muscles with otherwise long, parallel fascicles, and one muscle (m. iliopsoas) was capable of moderately high power in B. variegatus. The architectural properties observed in the hip flexors and extensors match well with roles in suspensory braking and vertical propulsion, respectively, whereas strong knee flexors and digital flexors appear to be the main muscles providing suspensory support in the pelvic limb. With aid in support by the forelimbs and the use of adaptive slow locomotion and slow muscle fiber recruitment patterns, structure–function in the tensile limb systems of sloths appears to collectively represent an additional mechanism for energy conservation. |
format | Online Article Text |
id | pubmed-10439369 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2023 |
publisher | John Wiley and Sons Inc. |
record_format | MEDLINE/PubMed |
spelling | pubmed-104393692023-08-20 Muscle architectural properties indicate a primary role in support for the pelvic limb of three‐toed sloths (Bradypus variegatus) Morgan, D. M. Spainhower, K. B. Mossor, A. M. Avey‐Arroyo, J. A. Butcher, M. T. J Anat Original Articles Tree sloths evolved below‐branch locomotion making them one of few mammalian taxa beyond primates for which suspension is nearly obligatory. Suspension requires strong limb flexor muscles that provide both propulsion and braking/support, and available locomotor kinetics data indicate that these roles differ between fore‐ and hindlimb pairs. Muscle structure in the pelvic limb is hypothesized to be a key anatomical correlate of function in braking/support during suspensory walking and propulsion and/or support during vertical climbing. This expectation was tested by quantifying architecture properties in the hindlimb limb musculature of brown‐throated three‐toed sloths (Bradypus variegatus: N = 7) to distinguish the roles of the flexor/extensor functional muscle groups at each joint. Measurements of muscle moment arm (r (m)), mass, belly length, fascicle length, pennation angle, and physiological cross‐sectional area (PCSA) were taken from n = 45 muscles. Overall, most muscles studied show properties for contractile excursion and fast joint rotational velocity. However, the flexor musculature is more massive (p = 0.048) and has larger PCSA (p = 0.003) than the extensors, especially at the knee joint and digits where well‐developed and strong flexors are capable of applying large joint torque. Moreover, selected hip flexors/extensors and knee flexors have modified long r (m) that can amplify applied joint torque in muscles with otherwise long, parallel fascicles, and one muscle (m. iliopsoas) was capable of moderately high power in B. variegatus. The architectural properties observed in the hip flexors and extensors match well with roles in suspensory braking and vertical propulsion, respectively, whereas strong knee flexors and digital flexors appear to be the main muscles providing suspensory support in the pelvic limb. With aid in support by the forelimbs and the use of adaptive slow locomotion and slow muscle fiber recruitment patterns, structure–function in the tensile limb systems of sloths appears to collectively represent an additional mechanism for energy conservation. John Wiley and Sons Inc. 2023-05-15 /pmc/articles/PMC10439369/ /pubmed/37190673 http://dx.doi.org/10.1111/joa.13884 Text en © 2023 The Authors. Journal of Anatomy published by John Wiley & Sons Ltd on behalf of Anatomical Society. https://creativecommons.org/licenses/by-nc-nd/4.0/This is an open access article under the terms of the http://creativecommons.org/licenses/by-nc-nd/4.0/ (https://creativecommons.org/licenses/by-nc-nd/4.0/) License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non‐commercial and no modifications or adaptations are made. |
spellingShingle | Original Articles Morgan, D. M. Spainhower, K. B. Mossor, A. M. Avey‐Arroyo, J. A. Butcher, M. T. Muscle architectural properties indicate a primary role in support for the pelvic limb of three‐toed sloths (Bradypus variegatus) |
title | Muscle architectural properties indicate a primary role in support for the pelvic limb of three‐toed sloths (Bradypus variegatus) |
title_full | Muscle architectural properties indicate a primary role in support for the pelvic limb of three‐toed sloths (Bradypus variegatus) |
title_fullStr | Muscle architectural properties indicate a primary role in support for the pelvic limb of three‐toed sloths (Bradypus variegatus) |
title_full_unstemmed | Muscle architectural properties indicate a primary role in support for the pelvic limb of three‐toed sloths (Bradypus variegatus) |
title_short | Muscle architectural properties indicate a primary role in support for the pelvic limb of three‐toed sloths (Bradypus variegatus) |
title_sort | muscle architectural properties indicate a primary role in support for the pelvic limb of three‐toed sloths (bradypus variegatus) |
topic | Original Articles |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10439369/ https://www.ncbi.nlm.nih.gov/pubmed/37190673 http://dx.doi.org/10.1111/joa.13884 |
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