A comparison of the moment arms of pelvic limb muscles in horses bred for acceleration (Quarter Horse) and endurance (Arab).
Abstract: Selective breeding for performance has resulted in distinct breeds of horse, such as the Quarter Horse (bred for acceleration) and the Arab (bred for endurance). Rapid acceleration, seen during Quarter Horse racing, requires fast powerful muscular contraction and the generation of large joint torques, particularly by the hind limb muscles. This study compared hind limb moment arm lengths in the Quarter Horse and Arab. We hypothesized that Quarter Horse hind limb extensor muscles would have longer moment arms when compared to the Arab, conferring a greater potential for torque generation at the hip, stifle and tarsus during limb extension. Six Quarter Horse and six Arab hind limbs were dissected to determine muscle moment arm lengths for the following muscles: gluteus medius, biceps femoris, semitendinosus, vastus lateralis, gastrocnemius (medialis and lateralis) and tibialis cranialis. The moment arms of biceps femoris (acting at the hip) and gastrocnemius lateralis (acting at the stifle) were significantly longer in the Quarter Horse, although the length of the remaining muscle moment arms were similar in both breeds of horse. All the Quarter Horse muscles were capable of generating greater muscle moments owing to their greater physiological cross-sectional area (PCSA) and therefore greater isometric force potential, which suggests that PCSA is a better determinant of muscle torque than moment arm length in these two breeds of horse. With the exception of gastrocnemius and tibialis cranialis, the observed muscle fascicle length to moment arm ratio (MFL : MA ratio) was greater for the Arab horse muscles. It appears that the Arab muscles have the potential to operate at slower velocities of contraction and hence generate greater force outputs when compared to the Quarter Horse muscles working over a similar range of joint motion; this would indicate that Arab hind limb muscles are optimized to function at maximum economy rather than maximum power output.
Publication Date: 2010-05-10 PubMed ID: 20492428PubMed Central: PMC2913009DOI: 10.1111/j.1469-7580.2010.01241.xGoogle Scholar: Lookup
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- Comparative Study
- Journal Article
Summary
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This study investigates how selective breeding for specific performance characteristics has affected the muscular structures in the hind limbs of two horse breeds: the Quarter Horse, bred for acceleration, and the Arab, bred for endurance. The research suggests that selective breeding has resulted in significant physical differences that offer each breed advantages in their respective specialties.
Methodology and Hypothesis
- The researchers hypothesized that the Quarter Horse, bred for quick accelerations, would have longer moment arms, the perpendicular distance from the line of action of the force to the pivot point, in their hind limb extensor muscles compared to the Arab. The longer the moment arm, the more torque a force can generate, so a longer moment arm in the hind limb extensor muscles could mean greater potential for fast, powerful muscular contractions.
- This study involved dissection of six hind limbs from both Quarter Horses and Arabs to determine muscle moment arm lengths for several key muscles: gluteus medius, biceps femoris, semitendinosus, vastus lateralis, gastrocnemius (medialis and lateralis) and tibialis cranialis.
Findings
- Results revealed that the moment arms of the biceps femoris (acting at the hip) and the gastrocnemius lateralis (acting at the stifle or knee) were significantly longer in the Quarter Horse, aligning with their hypothesis.
- However, the remaining muscle moment arm lengths were similar in both breeds, suggesting that other factors might also influence performance abilities.
- The Quarter Horse muscles were all found to be capable of generating greater muscle moments due to their larger physiological cross-sectional areas (PCSAs), meaning they have greater isometric force potential. This suggests that PCSA may be a better determinant of muscle torque than moment arm length in horses.
- The Arab horses had a greater muscle fascicle length to moment arm ratio (MFL : MA ratio) for all muscles except the gastrocnemius and tibialis cranialis. This could mean that Arab horses’ muscles are optimized to function at slower contraction velocities and generate greater force outputs, facilitating endurance as opposed to power output.
Cite This Article
APA
Crook TC, Cruickshank SE, McGowan CM, Stubbs N, Wilson AM, Hodson-Tole E, Payne RC.
(2010).
A comparison of the moment arms of pelvic limb muscles in horses bred for acceleration (Quarter Horse) and endurance (Arab).
J Anat, 217(1), 26-37.
https://doi.org/10.1111/j.1469-7580.2010.01241.x Publication
Researcher Affiliations
- Structure and Motion Lab, Royal Veterinary College, London, UK. tcrook@rvc.ac.uk
MeSH Terms
- Acceleration
- Animals
- Biometry / methods
- Breeding
- Female
- Hindlimb / physiology
- Hip Joint / physiology
- Horses / physiology
- Male
- Muscle Contraction / physiology
- Muscle, Skeletal / physiology
- Physical Endurance / physiology
- Range of Motion, Articular / physiology
- Torque
Grant Funding
- S20242 / Biotechnology and Biological Sciences Research Council
References
This article includes 35 references
Citations
This article has been cited 6 times.- Löffler L, Wölfer J, Gavrilei F, Nyakatura JA. Computational Modeling of Gluteus Medius Muscle Moment Arm in Caviomorph Rodents Reveals Ecomorphological Specializations. Front Bioeng Biotechnol 2022;10:806314.
- Granatosky MC, Ross CF. Differences in muscle mechanics underlie divergent optimality criteria between feeding and locomotor systems. J Anat 2020 Dec;237(6):1072-1086.
- Vögele AM, Zsoldos RR, Krüger B, Licka T. Novel Methods for Surface EMG Analysis and Exploration Based on Multi-Modal Gaussian Mixture Models. PLoS One 2016;11(6):e0157239.
- Sellers WI, Margetts L, Coria RA, Manning PL. March of the titans: the locomotor capabilities of sauropod dinosaurs. PLoS One 2013;8(10):e78733.
- Liu Y, Liu Y, Bai D, Dugarjaviin M, Zhang X. Transcriptomic Profiling Reveals Lysine-Mediated Proliferative Mechanisms in Mongolian Horse Myogenic Satellite Cells. Animals (Basel) 2025 Jun 9;15(12).
- Shitara T, Goto R, Ito K, Hirasaki E, Nakano Y. Hip medial rotator action of gluteus medius in Japanese macaque (Macaca fuscata) and implications to adaptive significance for quadrupedal walking in primates. J Anat 2022 Aug;241(2):407-419.
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