A comparison of the moment arms of pelvic limb muscles in horses bred for acceleration (Quarter Horse) and endurance (Arab)

Crook, T. C., Cruickshank, S. E., McGowan, C. M., Stubbs, N., Wilson, A. M., Hodson-Tole, E. and Payne, R. C. (2010) A comparison of the moment arms of pelvic limb muscles in horses bred for acceleration (Quarter Horse) and endurance (Arab). Journal of Anatomy, 217 1: 26-37. doi:10.1111/j.1469-7580.2010.01241.x


Author Crook, T. C.
Cruickshank, S. E.
McGowan, C. M.
Stubbs, N.
Wilson, A. M.
Hodson-Tole, E.
Payne, R. C.
Title A comparison of the moment arms of pelvic limb muscles in horses bred for acceleration (Quarter Horse) and endurance (Arab)
Journal name Journal of Anatomy   Check publisher's open access policy
ISSN 0021-8782
1469-7580
Publication date 2010-07
Sub-type Article (original research)
DOI 10.1111/j.1469-7580.2010.01241.x
Volume 217
Issue 1
Start page 26
End page 37
Total pages 12
Place of publication Oxford , U.K.
Publisher Wiley-Blackwell Publishing
Collection year 2011
Language eng
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.
Keyword Arab
Biomechanics
Equine
Locomotion
Moment arm
Muscle
Quarter Horse
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2011 Collection
School of Veterinary Science Publications
 
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Created: Sun, 11 Jul 2010, 00:04:58 EST