Contact and performance problems in horses are frequently attributed to the type of bit used, and there has been much research into horse interaction with the bit. Interaction between the horse and other parts of the bridle have been relatively neglected even though problems are often not resolved by alterations in bitting.
Traditional bridle design positions parts of the bridle over various anatomic prominences and moving parts of the head, it is therefore important to understand the interactions between parts of the bridle and the horse's head. Excessive noseband pressure in horses has been raised as an issue potentially affecting welfare, performance, and injury, particularly with respect to the use of crank nosebands with double bridles. However, there has been minimal scientific investigation performed. Various headpiece designs have been marketed that claim to reduce pressure around the headpiece and to improve performance as a result. However there appears to be little scientific research behind these claims.
The objectives of this study were three fold:
1. To determine the sites of maximum pressure under the headpiece of a double bridle, and under a standard crank cavesson noseband,
2. To design a double bridle headpiece and crank cavesson noseband combination that avoids sites of maximal pressure and
3. To compare the two bridles with regard to maximum pressure and equine gait kinematics (gait quality).
Two small format pressure mats were positioned, one underneath the headpiece and one over the horse's nasal bone underneath a cavesson crank noseband with the bridle fitted normally to the horse. Elite FEI level dressage and showjumping competition horses and riders were engaged. The magnitude and location of peak pressure for each pressure mat was recorded.
For all headpieces in all horses, high peak pressures were consistently located near the ends of the headpiece of the bridle on either side the head at the base of the ears. Interestingly additional locations of high peak pressure varied between headpiece designs. There were also frequent but intermittent high pressures recorded under the headpiece close to the junction with the browband, which was thought to be associated with movement of the tongue with swallowing actively creating pressures against the bridle. For all nosebands, peak pressures were consistently located either side of the nasal bone.
Horses wearing a bridle that was subsequently designed to avoid locations of maximum pressure exhibited a greater degree of carpal (knee) and tarsal (hock) flexion and a greater degree of forelimb protraction was seen. There was no alteration hindlimb protraction.
A marked difference was reported by 9 of 12 riders for straightness, for rhythm, suppleness, and impulsion, as well as for contact and collection with the new bridle.
Using a bridle designed to avoid locations of maximum pressure led to lower maximum pressure under the noseband and headpiece compared with the horse's usual bridle and was associated with improved gait quality at the trot, including greater carpal (knee) and tarsal (hock) flexion.
You can read a more in depth summary of this research here.