Muscle architecture and functional anatomy of the pelvic limb of the ostrich (Struthio camelus)

Abstract

The functional anatomy of the pelvic limb of the ostrich ( Struthio camelus ) was investigated in order to assess musculoskeletal specialization related to locomotor performance. The pelvic limbs of ten ostriches were dissected and detailed measurements of all muscle tendon units of the pelvic limb were made, including muscle mass, muscle length, fascicle length, pennation angle, tendon mass and tendon length. From these measurements other muscle properties such as muscle volume, physiological cross-sectional area (PCSA), tendon cross-sectional area, maximum isometric muscle force and tendon stress were derived, using standard relationships and published muscle data.Larger muscles tended to be located more proximally and had longer fascicle lengths and lower pennation angles.This led to an expected proximal to distal reduction in total muscle mass. An exception to this trend was the gastrocnemius muscle, which was found to have the largest volume and PCSA and also had the highest capacity for both force and power production. Generally high-power muscles were located more proximally in the limb, while some small distal muscles (tibialis cranialis and flexor perforatus digiti III), with short fibres, were found to have very high force generation capacities. The greatest proportion of pelvic muscle volume was for the hip extensors, while the highest capacity for force generation was observed in the extensors of the ankle, many of which were also in series with long tendons and thus were functionally suited to elastic energy storage.

Leg muscles that mediate stability: mechanics and control of two distal extensor muscles during obstacle negotiation in the guinea fowl

“…Short-fibred, pinnate distal muscles do have a substantial mass and work capacity in most animals (e.g. [16,17]). The gastrocnemius and digital flexors of the guinea fowl make up approximately 30 per cent of hindlimb muscle mass [12].…”

Differential muscular myosin heavy chain expression of the pectoral and pelvic girdles during early growth in the king penguin (Aptenodytes patagonicus) chick

“…Since the principal function of the ITC is to protract the femur (Torrella et al, 1998), this muscle should be recruited early to maintain a bipedal posture and to support the chick's body mass. In contrast, the GL muscle, which is involved in ankle extension and knee flexion, is essentially recruited for bipedal locomotion (Smith et al, 2006). At the time of emancipation (3-4weeks), the GL muscle appeared to be already mature, containing similar MyHC isoforms to adults.…”

“…The ITC arises from the anterior iliac crest and inserts on the patellar ligament (George and Berger, 1966). It is recruited for hip flexion and knee extension (Smith et al, 2006). The GL takes has its origin on the proximal surface of the fibular condyle of the femur and ends on the most lateral part of the tendo achilis (George and Berger, 1966).…”

“…The GL takes has its origin on the proximal surface of the fibular condyle of the femur and ends on the most lateral part of the tendo achilis (George and Berger, 1966). This muscle is mainly recruited for ankle extension and knee flexion (Smith et al, 2006).…”

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“…All the other birds 99 have three or four toes, while the largest avian biped ostrich has only two toes, the main 3rd 100 toe and the lateral 4th toe. Another unique adaptation at the distal part of the hindlimb is the 101 supra-jointed toe posture with the metatarsophalangeal joint and proximal phalanx of both 102 toes being permanently elevated above the ground surface (Schaller, et al, 2011;Deeming, 103 2003 (Schaller et al, 2007(Schaller et al, , 2011 Although a large number of studies have been conducted to investigate the ostrich hindlimb 112 kinematics during locomotion (Haughton, 1865;Alexander et al, 1979;Alexander, 1985;113 Gatesy and Biewener, 1991;Abourachid and Renous, 2000;Jindrich et al, 2007;Rubenson 114 et al, 2004Rubenson 114 et al, , 2007Rubenson 114 et al, , 2010Watson et al, 2011;Smith et al, 2006Smith et al, , 2007Smith et al, , 2010Smith et al, , 2013Schaller et 115 al., 2009Schaller et 115 al., , 2011Birn-Jeffery et al, 2014;Hutchinson et al, 2015), those kinematic analyses 116 were mainly focused on hip, knee and ankle joints. So far, little is known about the relative 117 motions of the 3rd and 4th toes intrinsic joints and the metatarsophalangeal joint during 118 ostrich foot locomotion.…”