Architectural properties of distal forelimb muscles in horses,Equus caballus

Abstract

Articular injuries in athletic horses are associated with large forces from ground impact and from muscular contraction. To accurately and noninvasively predict muscle and joint contact forces, a detailed model of musculoskeletal geometry and muscle architecture is required. Moreover, muscle architectural data can increase our understanding of the relationship between muscle structure and function in the equine distal forelimb. Muscle architectural data were collected from seven limbs obtained from five thoroughbred and thoroughbred-cross horses. Muscle belly rest length, tendon rest length, muscle volume, muscle fiber length, and pennation angle were measured for nine distal forelimb muscles. Physiological cross-sectional area (PCSA) was determined from muscle volume and muscle fiber length. The superficial and deep digital flexor muscles displayed markedly different muscle volumes (227 and 656 cm3, respectively), but their PCSAs were very similar due to a significant difference in muscle fiber length (i.e., the superficial digital flexor muscle had very short fibers, while those of the deep digital flexor muscle were relatively long). The ulnaris lateralis and flexor carpi ulnaris muscles had short fibers (17.4 and 18.3 mm, respectively). These actuators were strong (peak isometric force, Fmax=5,814 and 4,017 N, respectively) and stiff (tendon rest length to muscle fiber length, LT:LMF=5.3 and 2.1, respectively), and are probably well adapted to stabilizing the carpus during the stance phase of gait. In contrast, the flexor carpi radialis muscle displayed long fibers (89.7 mm), low peak isometric force (Fmax=555 N), and high stiffness (LT:LMF=1.6). Due to its long fibers and low Fmax, flexor carpi radialis appears to be better adapted to flexion and extension of the limb during the swing phase of gait than to stabilization of the carpus during stance. Including muscle architectural parameters in a musculoskeletal model of the equine distal forelimb may lead to more realistic estimates not only of the magnitudes of muscle forces, but also of the distribution of forces among the muscles crossing any given joint.

The architectural and functional specifications of intrinsic muscles of the fore limb of the Egyptian Baladi goats (Capra hircus)

“…This relative diminishment in distal limb mass is a steady component of animal adapted for rapid movement (Brown et al, 2003a;Pasi and Carrier, 2003;Payne et al, 2005 a and b) and supports the observation that high-speed animals have lighter distal limbs (Hildebrand and Hurley, 1985;Steudel, 1990).…”

“…This highlights the replacement of muscle volume with tendon. This phenomenon has been investigated before in various animals (Pasi and Carrier, 2003;Brown et al, 2003a;Payne et al, 2005a;Smith et al, 2006). This study demonstrated that fiber length and PCSA are considered to be a crucial muscle features.…”

Malakan Atlarında (Equus Caballus) Ön ve Arka Bacağın Distal’indeki Kasların Yapısal ve Fonksiyonel Özellikleri

“…Thus, the fact that muscles have small volume, short fibers and large PCSA shows that they have a high power generation capacity. Consequently, the force required for the muscle to be dynamic or static is produced by the muscles with a small volume and long tendons [7,8,23,24] . In the study, it was observed that the muscles in the distal of front and hind legs of Malakan horses generally had small volume, short fibers and high PCSA.…”

“…While the muscle structure may vary between different muscles of the individual [7,8] , the same muscles in different individuals can be different in terms of structure [9,10] . Also it is known that exercise [11] , genetic structure and gender [12] are effective on the characteristics of the muscle structure.…”

“…Burkholder [13] also add the muscle fiber volume, physiological characteristics, number of the fibers and their sequence to the factors affecting the structure of the muscle. Regarding the structural and functional properties of the muscles in Equidae family, Brown et al [7] and Payne et al [8] conducted a study on horses and Fayed [14] and Demiraslan and Özcan [15] conducted a study on donkeys. Also, the studies conducted on the muscle-tendon structure of four-leg animals is rather important in order to reveal the differences between the functions of front and hind legs [7,8] .…”