Coordination in the Limbs: How the Horse Moves

 


Although, humans and horses are both tetrapods, their locomotion can hardly be described in the same manner.  In humans, locomotion is bipedal and we generally look at the motion of one step.  In the horse, a quadruped, locomotion involves all four limbs and is described in terms of one limb cycle.  A limb cycle can be divided into two phases. The phase when the limb is in contact with the ground is stance phase.  This alternates with the swing phase when the limb is not in contact with the ground (Leach et al. 1984).

The stance phase can be further divided into two parts; the deceleration and propulsion phases.  The deceleration phase is defined as the point of heel contact to mid-stance position.  The mid-stance position is not necessarily the temporal mid-point of the stance phase.  It is marked by the point where the hoof is vertically beneath the hip joint in the hindlimb.  The propulsion phase occurs from the mid-stance position to toe-off (Fig. 1).


Figure 1. Limb Cycle of a Horse in Motion. Shown are the positionality of the horses limbs during 8 phases of motion. One full limb cycle is represented. Adapted from (Frederics et al. 1972)

 

A full limb cycle can also be described by stride. Stride duration can be described as the time required to complete just one stride.  There is no true definitive beginning or end to a stride.  Rather the beginning of a stride can be determined as any point in the pattern, making the end of the stride that exact instant of the next pattern (Robilliard et al. 2006).  Scientists have classified the common limb cycles of the horse into gaits.  

When scientists describe locomotion they often define motion in terms of the limbs and their relations to one another.  There are three common limb pairs that are described in relation to one another.  The diagonal limb pair is the frontlimb of one side and the hindlimb of the opposite side of a horse.  The ipsilateral limb pair is the frontlimb and hindlimb of the same side of the horse.  The contralateral limb pair is a limb of one side and a limb of the opposite side of the horse (Leach et al 1984).  

 
 
This website was created as a part of a class project in the Animal Physiology Class at Davidson College.