Dr Licka spoke in detail about the structural function of the back. Horses are not really designed to carry load on their back. The horses back is a complex structure designed to function to protect the horses as a grazing prey animal. Most importantly, the function of the back is to couple movements of the hind and fore limbs through the gaits and the muscles of the back are designed to stabilise the back through locomotion, not move it. Any movement of the back during locomotion is usually passive and as a result of hindlimb propulsion and forelimb impact forces.
So how does this relate to our everyday riding? Thinking initially about lameness, unsoundness or other low grade imbalances - overload injuries can occur in the muscles of the back as a consequence of the resulting functional trunck asymmetry these cause. If the hindlimb/forelimb patterns become unbalanced or abnormal the forces through the muscles of the back will become asymmetric as they attempt to stabilise the back against the imbalance. As these muscles become strained and potentially damaged, the forces can be transferred through the muscle attachments to the vertebrae and other structural points and these knock on effects can result in further compensations and pain. You can see that if we do not identify and treat the minor alterations we notice, they can quickly escalate. For this reason, do not dismiss subtle changes in your horse - favouring one rein, reluctance to canter or jump, becoming cold backed and moving away from tack.
Dr Licka also pointed out that fatigue can reduce the precision of coordination between and within muscles which can in turn lead to fibre damage. This is of course relevant for all muscle groups in the body but in relation to the back, where the relatively fragile structure is being asked to carry a sometimes unstable load, this can be a vital point to remember when schooling and working our horses.
Leading on from this, Dr Licka discussed the importance of the back muscles as they come in to contact with the saddle. As the back muscles come under pressure, the duration of the pressure can effect both the circulation and oxyenation of the area. So, as the duration of pressure increases, the circulation to the area decreases and oxygenation of the area is decreased (and we all know muscles need oxygen to function, right?). Elasticated girths can elongate pressure in certain areas so can therefore reduce muscle oxygenation. This tissue damage is also temperature dependant, so think carefully when using thick or numerous saddle pads which not only increase surface temperature beneath the saddle but can add an element of friction too.
This is also an important area to consider when bringing horses back in to work who may have reduced muscle tone and volume. (Think your typical horses who has been out of work for some time and is lacking in topline and shape through their back - those hollows at the base of the wither and lack of tone through the saddle region so the vertebrae appear to 'stick out'.) As the muscle volume is decreased, the chemical input of those muscles is decreased. As such the regional blood flow will be decreased, which reduces the muscles ability to counteract these pressure and temperature problems. It is so vital, when bringing horses back in to work, that we not only use the correct exercises to support the development of their muscles but ensure they have correctly fitted tack that is not adding undue pressure.
Dr Licka's talks were fascinating and really gave me a lot to think about when discussing schooling programmes and possible causes of injury with my clients.