For me, as a dedicated bitless bridle fitter, the discussion around rein tension is a key factor in the ongoing debate about bits versus bitless bridles.
I am grateful for the recent scientific commentary, What if Horses Were Humans? Comparing Rein Tension and Bit Pressures to Human Pressure Pain Thresholds, because it offers compelling data that clarifies why rein tension is so important—even when riding bitless. This study provides a strong foundation for promoting reduced tension across all forms of riding.
What Science Tells Us
The study required a method to measure the potential pain a horse experiences, as horses, being prey animals, are genetically programmed to mask their discomfort.
The researchers looked at established human pressure pain detection thresholds (PPDTs)—the minimum pressure perceived as painful—and compared them to published measurements of bit pressures and rein tensions on horses. This is based on the idea that the basic physiology of pain processing is fundamentally comparable across mammals.
Key Testing Takeaways
Only the lowest recorded rein tensions would likely be pain-free for humans.
The overall mean to maximum pressures commonly reported in the literature would induce strong to severe pain sensations in humans.
Exceeding Ethical Limits
The study noted that maximum rein tension values significantly exceed the pressure considered ethically acceptable in human studies, where higher pressures are expected to cause tissue damage.
The fact that pressures causing expected tissue damage in humans are commonly seen in riding is an undeniable welfare concern.
Application to Bitless
As a bitless fitter, I must emphasise that rein tension is still an essential factor in bitless bridles. Bitless systems work by applying pressure around various points on the head depending on the design and fit of the bridle, and studies have shown that this pressure can be stressful for the horse.
This research reinforces our goal, regardless of the type of headgear, to minimise contact and pressure.
A Positive Solution
The growing popularity of positive reinforcement training offers a path to naturally reduce rein tension. When we shift control from physical pressure to positive motivation and clear cues, we are far less likely to accidentally apply the pain-inducing pressure levels highlighted in this research.
This study presents a compelling, science-based case for a universal reduction in rein tension and fully supports the philosophy of partnership, built on the lightest possible contact.
As always, thanks for reading!
Study reference
Musial, F.; Weiss, T. What if Horses Were Humans? Comparing Rein Tension and Bit Pressures to Human Pressure Pain Thresholds. Animals 2025, 15, 2989. https://doi.org/10.3390/ani15202989
