Functional anatomy of the cheetah (Acinonyx jubatus) forelimb

Abstract

Despite the cheetah being the fastest living land mammal, we know remarkably little about how it attains such high top speeds (29 m s )1 ). Here we aim to describe and quantify the musculoskeletal anatomy of the cheetah forelimb and compare it to the racing greyhound, an animal of similar mass, but which can only attain a top speed of 17 m s. Measurements were made of muscle mass, fascicle length and moment arms, enabling calculations of muscle volume, physiological cross-sectional area (PCSA), and estimates of joint torques and rotational velocities. Bone lengths, masses and mid-shaft cross-sectional areas were also measured. Several species differences were observed and have been discussed, such as the long fibred serratus ventralis muscle in the cheetah, which we theorise may translate the scapula along the rib cage (as has been observed in domestic cats), thereby increasing the cheetah's effective limb length. The cheetah's proximal limb contained many large PCSA muscles with long moment arms, suggesting that this limb is resisting large ground reaction force joint torques and therefore is not functioning as a simple strut. Its structure may also reflect a need for control and stabilisation during the high-speed manoeuvring in hunting. The large digital flexors and extensors observed in the cheetah forelimb may be used to dig the digits into the ground, aiding with traction when galloping and manoeuvring.

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

“…Across the whole dataset, maximum stride frequencies of 3.9Hz were used by both species; a maximum that far exceeds that used by other fast quadrupeds (Heglund and Taylor, 1988;Witte et al, 2006) and that previously observed for the cheetah (Hildebrand, 1961). For both species, a linear increase in stride length with speed was observed, and the cheetah used longer stride lengths than the greyhound, which can be explained by the cheetah's slightly longer limbs and back (Hudson et al, 2011a;Hudson et al, 2011b). During a gallop, the greyhound therefore appears to only increase its stride length; however, the cheetah uses a combination of increased stride frequency and stride length to achieve higher speeds.…”

“…In contrast, the fastest canid, the racing greyhound (Canis familiaris L.), has a top speed of just 17ms -1 (Jayes and Alexander, 1982;Usherwood and Wilson, 2005), despite the two animals being of a similar mass and gross morphology. Anatomical studies (Hudson et al, 2011a;Hudson et al, 2011b) have presented no clear reason as to why there is such a large difference in their top speeds, and there is no clear consensus in the literature as to what fundamentally limits the maximum running speed of a quadruped. Here, we studied the kinematics and kinetics of galloping in the cheetah and racing greyhound to investigate how the cheetah attains faster speeds than the greyhound, and to explore some of the theorised limits to maximum running speed.…”

“…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). Finally, the recruitment of fast glycolytic or long muscle fibres that will contract at higher velocities than slow oxidative or short fibres will rotate the limb more rapidly.…”

Anatomical transverse magnetic resonance imaging study of ligaments in palmar surface of metacarpus in Miniature donkey: identification of a new ligament

“…Suspensory ligament, SDF and DDF muscles are all active during stance and are thought to support body weight [12].…”

Lion (Panthera leo) and caracal (Caracal caracal) type IIx single muscle fibre force and power exceed that of trained humans

“…Many biomechanical factors falling outside the scope of this study (each contributing to a different degree and related to species) could potentially affect power output and are worth mentioning. These include the mass of the animal, being quadrupedal or bipedal, lever arm angles and length of the limbs (affecting stride length), muscle and tendon lengths, and the ability to store elastic energy, to name but a few (Alexander, 2006;Hudson et al, 2011a;Hudson et al, 2011b).…”