Comparison of Rein Forces and Pressure Beneath the Noseband and Headpiece of a Snaffle Bridle and a Double Bridle

Information describing forces applied to the horse are needed to inform regulatory decisions regarding equine health and wellbeing. This study compares forces exerted beneath the noseband and headpiece of a snaffle bridle (SB) and a double bridle (DB). Horses were fitted with the same type of SB and DB. Forces were measured by pressure mats under the noseband (nasal/mandibular) and headpiece (occipital) of the bridle and by force sensors inserted bilaterally between the bit(s) and reins. The noseband was adjusted to 2 finger-equivalents using a tightness gauge. Data were recorded for eleven high-level dressage horses ridden in SB and DB in random order at collected walk, trot (sitting), and canter. The noseband pressures were similar between bridle types. Minimal, maximal, and mean occipital force and pressure were significantly higher for DB at walk, trot, and canter (all p ≤ 0.01), except minimal force for collected canter (p = 0.04). The rein tension for the bridoon bit alone and for the combined bridoon and curb bits was significantly lower than for the snaffle bit. Similar forces occur when ridden in SB and DB except that occipital force and pressure are higher due to the greater weight of the DB, and rein tension is lower for the DB.