Functional anatomy and muscle moment arms of the pelvic limb of an elite sprinting athlete: the racing greyhound (<i>Canis familiaris</i>)

Scratch-digging mammals are commonly described as having large, powerful forelimb muscles for applying high force to excavate earth, yet studies quantifying the architectural properties of the musculature are largely unavailable. To further test hypotheses about traits that represent specializations for scratch-digging, we quantified muscle architectural properties and myosin expression in the forelimb of the groundhog (Marmota monax), a digger that constructs semi-complex burrows. Architectural properties measured were muscle moment arm, muscle mass (MM), belly length (ML), fascicle length (l F ), pennation angle and physiological cross-sectional area (PCSA), and these metrics were used to estimate maximum isometric force, joint torque and power. Myosin heavy chain (MHC) isoform composition was determined in selected forelimb muscles by SDS-PAGE and densitometry analysis. Groundhogs have large limb retractors and elbow extensors that are capable of applying moderately high torque at the shoulder and elbow joints, respectively. Most of these muscles (e.g. latissimus dorsi and pectoralis superficialis) have high l F /ML ratios, indicating substantial shortening ability and moderate power. The unipennate triceps brachii long head has the largest PCSA and is capable of the highest joint torque at both the shoulder and elbow joints. The carpal and digital flexors show greater pennation and shorter fascicle lengths than the limb retractors and elbow extensors, resulting in higher PCSA/MM ratios and force production capacity. Moreover, the digital flexors have the capacity for both appreciable fascicle shortening and force production, indicating high muscle work potential. Overall, the forelimb musculature of the groundhog is capable of relatively low sustained force and power, and these properties are consistent with the findings of a predominant expression of the MHC-2A isoform. Aside from the apparent modifications to the digital flexors, the collective muscle properties observed are consistent with its behavioral classification as a lessspecialized burrower and these may be more representative of traits common to numerous rodents with burrowing habits or mammals with some fossorial ability.

Section: Muscle Functional Properties and Architectural Indexesmentioning

confidence: 95%

Section: Research Articlementioning

confidence: 96%

Forelimb muscle architecture and myosin isoform composition in the groundhog (Marmota monax)

Rupert

Rose

Organ

et al. 2014

“…There are several adaptations that can minimise the muscular work required to swing the limb, some of which have been observed in both the cheetah and greyhound. Reduced distal limb mass is observed in both species and will reduce the inertia of the limb (Hudson et al, 2011a;Hudson et al, 2011b;Williams et al, 2008a;Williams et al, 2008b). Muscle insertions that are close to the joint will allow faster joint rotational velocities for a given change in muscle length and are observed in the greyhound, but the cheetah hip and shoulder muscles tend to have long moment arms by comparison (Hudson et al, 2011a;Hudson et al, 2011b).…”

Section: Introductionmentioning

confidence: 99%

“…Two studies have investigated limb forces during galloping in dogs (Bryant et al, 1987;Walter and Carrier, 2007), but none have examined steady-state galloping in the greyhound, which has a highly specialised morphology compared with other canids (Williams et al, 2008a;Williams et al, 2008b).…”

Section: Introductionmentioning

confidence: 99%

High speed galloping in the cheetah (Acinonyx jubatus) and the racing greyhound (Canis familiaris): spatio-temporal and kinetic characteristics

Hudson

Corr

Wilson

2012

128

116

SUMMARYThe cheetah and racing greyhound are of a similar size and gross morphology and yet the cheetah is able to achieve a far higher top speed. We compared the kinematics and kinetics of galloping in the cheetah and greyhound to investigate how the cheetah can attain such remarkable maximum speeds. This also presented an opportunity to investigate some of the potential limits to maximum running speed in quadrupeds, which remain poorly understood. By combining force plate and high speed video data of galloping cheetahs and greyhounds, we show how the cheetah uses a lower stride frequency/longer stride length than the greyhound at any given speed. In some trials, the cheetahs used swing times as low as those of the greyhounds (0.2s) so the cheetah has scope to use higher stride frequencies (up to 4.0Hz), which may contribute to it having a higher top speed that the greyhound. Weight distribution between the animalʼs limbs varied with increasing speed. At high speed, the hindlimbs support the majority of the animalʼs body weight, with the cheetah supporting 70% of its body weight on its hindlimbs at 18ms -1 ; however, the greyhound hindlimbs support just 62% of its body weight. Supporting a greater proportion of body weight on a particular limb is likely to reduce the risk of slipping during propulsive efforts. Our results demonstrate several features of galloping and highlight differences between the cheetah and greyhound that may account for the cheetahʼs faster maximum speeds.

“…Several studies have investigated the muscle-tendon architecture of the canid hindlimb (Shahar and Milgram, 2001) and its effect on speed and power generation (Kemp et al, 2005;Pasi and Carrier, 2003;Williams et al, 2008), but the role of comparative functional anatomy in promoting locomotor economy across dog breeds and canids in general remains largely unexplored. Here, we speculate that specialized tendon loading and energy recovery may provide a natural mechanism enabling wolves and other large canids to track prey over long distances (e.g.…”

Section: Discussionmentioning

confidence: 99%

Comparative locomotor costs of domestic dogs reveal energetic economy of wolf-like breeds

Bryce

Williams

2016

The broad diversity in morphology and geographic distribution of the 35 free-ranging members of the family Canidae is only rivaled by that of the domesticated dog, Canis lupus familiaris. Considered to be among nature's most elite endurance athletes, both domestic and wild canids provide a unique opportunity to examine the variability in mammalian aerobic exercise performance and energy expenditure. To determine the potential effects of domestication and selective breeding on locomotor gait and economy in canids, we measured the kinematics and mass-specific metabolism of three large (>20 kg) dog breed groups (northern breeds, retrievers and hounds) of varying morphological and genomic relatedness to their shared progenitor, the gray wolf. By measuring all individuals moving in preferred steady-state gaits along a level transect and on a treadmill, we found distinct biomechanical, kinematic and energetic patterns for each breed group. While all groups exhibited reduced total cost of transport (COT) at faster speeds, the total COT and net COT during trotting and galloping were significantly lower for northern breed dogs , respectively). These results suggest that, in addition to their close genetic and morphological ties to gray wolves, northern breed dogs have retained highly cursorial kinematic and physiological traits that promote economical movement across the landscape.