Current practices for fitting a saddle prior to competition is to tighten the girth to a level that does not allow the saddle to slip. The effects of a tight girth on the performance of the horse has not previously been studied but some horse trainers have suggested that a very tight girth reduces the performance of horses. Researchers from the Mornington Peninsula Horse Hospital and The University of Melbourne Veterinary Clinical Centre have conducted a study that looks at the exercise capacity of horses in respect to how tightly the girth is done up.
Eight horses were used in this study and these horses were either Thoroughbred or Standardbred. A series of treadmill exercise tests were conducted over a number of weeks with one week separating each test. For each exercise test horses were fitted with a racing saddle and a girth tension of either 5, 10, 15 or 20 kg was randomly allocated to each horse.
A previous study by the authors has shown that the usual tension applied to keep a saddle on Thoroughbred racehorse is 13kg. The current study found that the run-to-fatigue times and distances were reduced with increased tension of the girth suggesting that overtightening the girth does cause a reduction in the performance of the horse. However it was found that there was no difference to the degree that performance was reduced as the tension exceeded 10kg.
The reason for this is unclear but the authors suggest that at girth tensions above 10kg the soft tissue and fluid within the thoracic wall may be displaced during exercise minimising the effect of further thoracic constriction. An alternative explanation suggested is that when the girth is tightened at or above 10kg the horse may be forced into alternate breathing strategies such as greater use of the diaphragm, which may offset further declines in performance.
The reason that overtightening of the girth causes poor performance is not yet known and there was some variability in the susceptibility of horses to overtightening of the girth and although most horses were affected to some degree, one horse was not affected. The reason for this may relate to chest wall configuration or the ability to compensate by developing other breathing strategies in the face of chest wall restriction. The authors note that saddle placement may exert a substantial influence on results, especially as the saddle is placed further back where there is normally a greater range of thoracic wall motion.
This is an area that certainly warrants more study. Even though the run-to-fatigue test is a way to assess performance in horses it must be remembered that this does not reflect the exact circumstances of racing. In sprint racing the effect of the girth tension may have little or no effect whereas it is likely to have an adverse effects over greater distances. It must be pointed out that safety for the rider is the greatest priority when fitting a saddle to any horse.