Hip medial rotator action of gluteus medius in Japanese macaque (Macaca fuscata) and implications to adaptive significance for quadrupedal walking in primates

The gluteus medius (GM) muscle in quadrupedal primates has long been thought to mainly act as a hip extensor. However, previous reports argue that it may be a prime hip medial rotator and functions to rotate the pelvis in the horizontal plane, suggesting the functional differentiation between the GM...

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Bibliographic Details
Published in:Journal of anatomy 2022-08, Vol.241 (2), p.407-419
Main Authors: Shitara, Tetsuya, Goto, Ryosuke, Ito, Kohta, Hirasaki, Eishi, Nakano, Yoshihiko
Format: Article
Language:English
Subjects:
Adaptiveness
Arm
Electromyography
gluteus medius
Hip
hip extensors
hip medial rotation
Japanese macaque
locomotion
Macaca fuscata
Muscle contraction
muscle moment arm
Original
Pelvis
Walking
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Summary:The gluteus medius (GM) muscle in quadrupedal primates has long been thought to mainly act as a hip extensor. However, previous reports argue that it may be a prime hip medial rotator and functions to rotate the pelvis in the horizontal plane, suggesting the functional differentiation between the GM and other hip extensors as hamstrings. In this study, we aim to quantify the muscle actions of the GM and hamstrings using muscle moment arm lengths and discuss the functional differentiation among hip extensors. Muscle attachment sites of eight specimens of Japanese macaque (Macaca fuscata) were digitized, and musculoskeletal models were constructed. Flexor‐extensor, abductor‐adductor, and medial‐lateral rotator moment arms were calculated as the models were moved following the experimentally acquired kinematic data during walking on a pole substrate. Using electromyography, we also recorded the pattern of muscle activation. The GM showed a larger medial rotator moment arm length than the extensor moment arm length when it was activated, suggesting this muscle acts mainly as a hip medial rotator rather than as a hip extensor. The medial rotator action of the GM in the early support phase may rotate the pelvis in the horizontal plane and function to help contralateral forelimb reaching as a previous study suggested and facilitate contralateral hindlimb swinging to place the foot near the ipsilateral forelimb's hand. Comparison of percentages of moment arm lengths for each muscle. The gluteus medius (GM) of Japanese macaque had a large percentage on the medial rotator moment arm, suggesting the GM mainly acts on hip medial rotation. Hamstrings tended to have a large percentage on the extensor moment arm, meaning they mainly act as hip extensors.
ISSN:0021-8782
1469-7580
1469-7580
DOI:10.1111/joa.13658