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Quadrupedal Mechanics - Anatomy & Physiology (view source)
Revision as of 03:43, 29 November 2013
, 03:43, 29 November 2013→Propulsive force
==='''Propulsive force'''===
==='''Propulsive force'''===
A propulsive force, applied to the limb to retract it, propels the animal over the ground. Opposing the propulsive force is friction force, acting between the animal body and the ground. It is the friction force that acts in the direction of movement. This is best visualised by interposing a plate between the animal and the ground (Fig. 10.6). When there is no friction between the plate and the ground, the propulsive force accelerates the plate and not the animal body. If the friction force equals the propulsion force, the plate remains at rest, and the animal is accelerated. Friction, which is usually thought to oppose motion, is essential for locomotion. The construction of the surface contact with the ground is vitally important and is often a source of breakdown in running animals, just as it is for motor vehicles.
A propulsive force, applied to the limb to retract it, propels the animal over the ground. Opposing the propulsive force is friction force, acting between the animal body and the ground. It is the friction force that acts in the direction of movement. This is best visualised by interposing a plate between the animal and the ground (Fig. 10.6). When there is no friction between the plate and the ground, the propulsive force accelerates the plate and not the animal body. If the friction force equals the propulsion force, the plate remains at rest, and the animal is accelerated. Friction, which is usually thought to oppose motion, is essential for locomotion. The construction of the surface contact with the ground is vitally important and is often a source of breakdown in running animals, just as it is for motor vehicles.
[[File:QMFig 10.7.png|thumb|'''Fig 10.7 The propulsive apparatus of the greyhound''']]
In animals that use their vertebral column in running, the fore and hindlimb pendulums swing about a pivot near the thoracolumbar junction (Fig. 10.7). Axial muscles and extrinsic limb muscles acting over this pivot produce the propulsive thrust.
In animals that use their vertebral column in running, the fore and hindlimb pendulums swing about a pivot near the thoracolumbar junction (Fig. 10.7). Axial muscles and extrinsic limb muscles acting over this pivot produce the propulsive thrust.
:::::(a) Hindlimb. Retraction is brought about by the extensors of the vertebral column (x, m. longissimus and its dorsal aponeurosis) and the extensors of the hip (y, the middle gluteal muscle and z, the caudal thigh muscles).
:::::(a) Hindlimb. Retraction is brought about by the extensors of the vertebral column (x, m. longissimus and its dorsal aponeurosis) and the extensors of the hip (y, the middle gluteal muscle and z, the caudal thigh muscles).
:::::(b) Forelimb. Retraction is brought about by the flexors of the vertebral column (w, the external abdominal oblique muscle and x, rectus abdominis), and suitably placed muscles of the forelimb (y, latissimus dorsi and z, the deep pectoral muscle).
:::::(b) Forelimb. Retraction is brought about by the flexors of the vertebral column (w, the external abdominal oblique muscle and x, rectus abdominis), and suitably placed muscles of the forelimb (y, latissimus dorsi and z, the deep pectoral muscle).
==='''Gaits'''===
==='''Gaits'''===