The effect of different head carriages on horses’ airways *H&H Plus*

  • What effect does dressage head and neck position have on a horse’s airway? Peter Green MRCVS finds out, in his latest research round-up

    At the higher levels of dressage, the horse is asked to perform strenuously while his airway is not straight; it is kinked at the throat, where the head and neck meet.

    There has been much debate about whether the competition outline and head carriage expected in dressage is natural or unnatural and whether the airway is compromised. In 2010, the FEI held a round table conference at which hyperflexion was deemed unacceptable – hyperflexion being the forcing of the horse’s head into a position beyond the vertical, with the chin pulled into the chest.

    Rather, the “low-deep-round” (LDR) position has been promoted as a warm-up tool, because it is believed to be more natural and less forced by unreasonable tension on the reins.

    Danish vets have investigated the performance, function and welfare of dressage horses and a recent paper has shed more light on this controversial subject. They studied 13 high-performance warmblood dressage horses competing at prix st georges or higher. Each was fitted with a tiny, indwelling (internal) endoscope, to monitor airway function, and with tension gauges in the reins.

    The horses were ridden by their usual competition riders, using only a snaffle bit. Each was worked in four different positions: free head carriage, in which the head was completely unrestrained; competition frame, in which the poll was high and the front of the face vertical; LDR, in which the neck was low and round with the poll below the level of the withers and the front of the face beyond the vertical and, finally, hyperflexion, in which the horse was asked to flex his neck as much as possible with the front of his face beyond the vertical.

    The horses were studied at halt, walk, trot and canter, with rein tension and airway obstruction measured for every position and in every pace.

    Measuring tension

    There was good correlation between all the horse-rider pairs, with none of the riders using excessive rein tension.

    Overall, more rein tension was required at canter to maintain any of the head-neck positions, compared with other gaits, and the least at trot. For these elite horses, the least rein tension was required to maintain the free head carriage position across all gaits.

    Both the competition frame and hyperflexion required significantly greater rein pressure than LDR, which confirms the FEI advice that LDR is a more natural posture for the horse. This difference was quite marked: measured in newtons, the median tension required for all gaits was 5.46 for unrestrained head carriage, 20.52 for competition frame, 20.76 for hyperflexion and only 8.22 for LDR.

    The vets looked for changes that would restrict airflow, such as instability of the palate, collapse of the throat and pinching of the entrance to the trachea. They found that trot was the gait in which airflow was most restricted, followed by canter, walk and halt.

    When the performance of the airway in the various head and neck positions was compared, the position with the lowest incidence of problems was the free head carriage. What came as a surprise was that hyperflexion did not significantly increase the incidence of airway problems compared with the competition frame. In fact, competition frame caused marginally more problems than hyperflexion, although the difference between these two, again, was not great.

    LDR gave rise to fewer airway problems compared with both competition frame and hyperflexion, even though at LDR the front of the horse’s face is behind the vertical.

    We must be cautious in interpreting these results. These horses were competing at a high level and none showed any evidence of suffering from clinical airway obstruction that affected their performance. The changes in their palates and throats would not have been detected without the indwelling endoscope.

    We know that many horses working in different disciplines are affected by such problems and these results do not suggest that dressage is any better or worse than any other equine sport. The sample size was small, at just 13 horses, but the results from this study were clear: apart from a completely unrestrained head, LDR is the position that has the least effect on the horse’s airway.

    The researchers state that further studies are needed to evaluate whether dynamic structural disorders are a result of flexion or if the degree of flexion has an impact.

    Ref Horse & Hound; 7 May 2020