updated: 2022-02-09 10:06:50
Does your therapist consciously help your horse to load their limbs correctly?
The final stage of the swing phase has a lot to do with how the hoof strikes the ground. Through exercises which deliberately target the swing phase we can influence and improve impact with the ground and therefore the forces that are transferred through the limb joints. During assessment we tend to focus on how the limbs are moving and landing with a large amount of focus centred around the stance phase. While it is true that if we can influence how our horses bear weight then we can influence the forces that are transferred up the limb, it is also very important to ensure enough attention is paid to the swing phase and the preparation of loading.
What affects the swing phase?
During the swing phase of the stride the limb should pass through a good range of movement. As well as maximal protraction and retraction we should also be considering the flight arc. A low flight arc, where the limb travels low to the ground or even drags, is undesirable. This can be a sign of pathology and pain but also weakness or poor motor control.
During rehabilitation, once the primary issue is resolved and pain is controlled, the horse is often left with a poor swing phase which requires retraining.
Initial protraction of the limb is instigated by elastic energy during the first part of the swing phase but in walk especially, where there is significant muscle contribution required for the limb to reach its highest point and produce a nice flight arc. Therefore, lack of muscle strength and control can lead to a low flight arc.
Peak flexion of the limb joints occurs during the swing phase so it makes perfect sense that a lack of range of movement (ROM) will affect the swing of the limb. Range of movement may be restricted through pain, joint instability, muscle imbalance, poor motor control and feedback. If the limb can’t ‘fold up’ effectively, due to any of the above then there will be a lower or altered flight arc and probably some compensations occurring elsewhere.
As the limb moves into the final part of the swing phase, it starts to prepare for loading. The focus in most rehab is on improving ROM and positive (concentric) muscle strengthening. While this is important in increasing flexion and power, it is essential that deceleration, the negative contraction and limb control are all equally included. It is possible to have lots of power in push off and optimal flexion of the joints but then what happens to the limb in preparation for ground strike? Is there too much control? Or not enough?
Swing phase retraction
The final part of the swing phase is ‘swing phase retraction’. This is where the limb is pulled backwards prior to landing. It reduces the horizontal velocity and prepares the hoof to land in the right place, optimising the forces that travel up the limb.
There are a number of ways that irregularities in this stage of the swing phase can present:
A horse with heel pain may be overactive in this phase. They will present with a shortened stride, causing ‘toe first’ landing and affecting the forces through the limb joints.
Addressing the primary problem will not always see a full return to normal movement as these movement pathways have been well ingrained and this is where rehab comes in. In this case the aim would be to increase protraction and the speed at which the limb travels forward and reduce the overactive retraction to a normal level. At the other end of the spectrum some horses have lost control over this phase. This can be due to protractor retractor muscle imbalance, weakness in the retractors or core strength to name a few.
It is not always so obvious to see but this lack of controlled swing retraction and therefore loading, can lead to variable hoof placement, seen as a foot slap rather than nice placement. Due to the lack of reduced horizontal velocity, the horses in this scenario can also commonly slip and slide especially on a non-grip surface. If this was the case, promotion of a controlled swing retraction is paramount.
What can your therapist do to influence this stage of the swing phase and better prepare the limb for loading?
It is less about learning any new magic exercises and more about being intentional about allocating the exercises we already use with the aim of influencing this phase. Some examples of exercises that can be used to influence swing phase preparatory loading are:
It's common to consider leg weights for strengthening of the hip and elbow flexors but they also have the added benefit of increasing negative (eccentric) work to help control the movement of the limb. The weights increase forward momentum of the limb so there is extra effort required to pull the limb backwards to the ground. Therefore, careful and appropriate use of leg weights may be useful in patients who have trouble controlling swing retraction, therefore slapping the hoof.
Using resistance training will help to increase force and speed of protraction in those who are retracting their limb too early in the swing phase. Resistance can be applied to horses with resistance bands. Also, using the resistance of water is useful in these cases but the water needs to be deep enough so that they cannot step out and over it (consult a hydrotherapist).
Walking downhill recruits the retractor muscles and relies more heavily on negative (eccentric) muscle strength and control. To progress this exercise, poles can be added on the hill and then steps down. These exercises require the horse to pull the limb back against the ground to counteract the increased gravitational forces, so are very useful for those who have a lack of control in swing retraction.
Poles and cavalettis have become heavily utilised in rehab and training. It is vital to observe the horse closely when setting pole work and evaluate
how they are using their bodies to navigate through the obstacles. Quadrupeds are very good at cheating and it is essential attention is paid
to HOW they get over the obstacles rather than just the fact that they can (or can’t).
Poor pole or cavaletti work will just reinforce the poor patterns we are trying to break.
Generally, those with overactive swing retraction will benefit from low poles but gradually moving the distances further apart to encourage reach. You can have closely spaced raised poles in one set and low poles which are spaced further apart in another set. With a little creative thinking, it is possible to develop exercises that can influence the way the limb moves through the air and therefore influences how it strikes the ground. Of course, there is more to add to this: abduction and adduction, flexion and extension of individual joints, core strength etc.
But this is a good place to start!