This 2025 study compared rein tension and bit pressure in horses  to known human pressure pain thresholds . The key finding: most commonly reported rein pressures in equestrian sport exceed the level at which humans would perceive pain , and higher ranges could reach levels associated with severe pain or even tissue damage. Only the lowest rein tensions would likely be pain-free if applied to a human face or hand. Bit pressure and rein tension are increasingly discussed in