How tight is your horse's noseband?
It has become common practice for many horse owners to use crank, drop, grackle, Mexican or flash nosebands to strap their horse's mouth shut. So much so, that it is actually quite difficult to find a bridle with a normal cavesson noseband in tack shops – bridles now seem to come with a flash noseband as standard.
Horses open their mouth to avoid bit pain, so strapping them shut to attempt to gain more control is simply putting a sticking plaster on a symptom. We should be looking at why the horse is 'difficult' to control or is avoiding the bit in the first place.
At most dressage competitions you will see horses wearing crank nosebands fastened so tightly that they cannot open their mouth at all. Opening the mouth, teeth grinding and crossing the jaw to avoid the bit are all signs of stress and tension in the horse, so dressage riders are trying to hide these behaviours as they may well be marked down.
"Extreme tightening of the noseband may force the mucous membranes lining the cheek against the molar teeth and is thought to increase the bitted horse’s compliance and responsiveness to rein pressure, perhaps by sensitising its mouth (Randle & McGreevy, 2011).
Recent evidence suggests that horses wearing tight nosebands undergo a physiological stress response, are sensitised to bit pressure and may have reduced blood flow (McGreevy et al., 2012). Consequently, on welfare grounds, the use of nosebands that constrict with potential to cause injuries should not be permitted in training or competition."
In a brilliant initiative, the International Society for Equitation Science has developed a Noseband Taper Gauge which they suggest should be used at all competitions to ensure nosebands are not restrictive. A steward could use the gauge to uniformly check all riders comply before entering the ring.
You can find more information on the ISES website here: http://www.equitationscience.com/restrictive-nosebands