In this episode, Dr David Marlin takes us inside the findings of a ground-breaking new research paper titled “Comparison of Rein Forces and Pressure Beneath the Noseband and Headpiece of a Snaffle Bridle and a Double Bridle”, recently published in the journal Animals.
Amidst ongoing public debate and controversy surrounding the use of double bridles in dressage, David shares how this study aimed to put assumptions to the test with science. Working with a team of researchers and high-level dressage horses, the study compared rein tension and pressure at key contact points across both snaffle and double bridles.
David also tackles common misconceptions about bit mechanics, explaining why the curb bit is a class one lever with a floating fulcrum, not the “nutcracker” some claim it to be. He discusses the ethics of research publishing, the importance of evidence-based conclusions, and his hopes for a more flexible and welfare-focused approach to bridle use in sport.
This is a must-listen for anyone interested in equine science, dressage, and horse welfare. The study was funded by Hartpury University and the British Equestrian Federation, and the full paper is freely available online. Follow this link to read more about it – New Study Reveals Similarities in Rein Tension and Noseband Pressure Between Snaffle and Double Bridles
Transcription
Here is a transcription of the podcast. (Please note this is an automated transcription, so we apologise for any errors from the original podcast.)
Hi, in this podcast I’m going to talk about some of our research that’s recently been published and in particular a paper entitled Comparison of Rain Forces and Pressure Beneath the Noseband and Headpiece of a Snaffle Bridal and Double Bridal and this was recently published in the scientific journal Animals and the authors are Russell McKenney-Guire, Henry Clayton, Jane Williams, myself
Mark Fisher, Diana Fisher, Victoria Walker and Rachel Murray. Now dressage has obviously been in focus quite a lot, not necessarily for good reasons recently. There’s been the publication of many different photos of horses with discoloured tongues, what’s become known as blue tongue. And there’s also been a lot of focus on the use of double bridles. Now this is research that’s been going on for
a year or so that we’ve been involved in and we’ve just published this first sort of paper which gives a really important insight into what’s going on with the double bridle and how this compares to snaffle. And the premise really is that most people who seem to be criticizing the double bridle are saying that the snaffle bridle is much kinder, much gentler. Now
That we don’t know that that’s a theory. So we’ve actually set out to test that theory. So what did we actually do in this study? Well, we took 11 high level dressage horses and these were fitted either with a snaffle bridle or a double bridle. We did this in sort of random order. So what we call a crossover design, half of them were first written in the snaffle and then in the double.
and half of them were first ridden in the double and then in the snaffle. And what’s important to know is that all of these horses were used to being ridden in both a snaffle and a double. Now, what we measured was the pressure beneath the noseband and the pressure underneath the headpiece using small pressure mats and using what’s called the appliance system.
the other main pressure system is the tech scan system and then we measured the rain tensions on the left and right snaffle and on the left and right snaffle on the what we call a bradoon and the left and right kerb in terms of when they’re ridden in the double. Now this is this part of the study is what I was responsible for we use very small sensors
Force sensors that we place between the bit rings and the rain These weigh around 25 grams so they don’t really alter the riders or the horses experience of what’s going on and We sample that force that tension a hundred times a second and we’re able then to transmit this wirelessly to a computer and
and we recalled those rain tensions over time. We then processed those signals to look at things like the average tension, the minimum tension and the maximum tension. And we got the riders to obviously warm up the horses and then they rode down the long side of a school in collected walk, collected trot and collected canter on both reins.
Now the main findings from this study were that the upper and lower nose band pressures were similar for both the snaffle and the double bridle. The headpiece forces were slightly higher for the double bridle but this is probably due to the fact that the double bridle weighs around two kilos and the snaffle bridle
weighs around one kilogram and if we look at the difference between the two signals you can see it’s equivalent to about one kilogram so it’s likely that this is due to the the difference in weight of the bridles. Now if we look at the total rain tension so that’s if we’re talking about the the snafl on its own that’s the sum of the left and right snafl tensions and if we’re talking about the double
we’re talking about the left and right bradoon plus the left and right kerb in walk and canter there was no difference and actually in trot the total force was lower for the double bridle now this is interesting as in the case of the double bridle this means that the total force is being distributed over the two bits so if we look the bradoon
is the still the higher one but the bradoon is lower than the snaffle on its own and the difference is made up by the kerb and the kerb tends to be about half the the tension of being put on the bradoon so the kerb forces are lower than the bradoon which would be we would consider demonstrates that the kerb bit is being used correctly
Now there’s going to be lots of questions there already have been lots of questions. People have said well you’ve only looked at you know walk trot and canter actually we didn’t we also looked at trot halt transition we also looked at passage and pf and what’s really interesting is that we see once again the same as with the walk trot and canter
the average rain tensions in particular and the head pieces pressures don’t differ between those, the snaffle and the double. So it’s even in more complex movements, the snaffle and the double, we’re really not seeing any difference. Now, what we also need to understand in the future is
whether we get the same results with less experienced riders. So these were high level riders on high level horses. Actually that study has already been completed and we’re analyzing the data now. Now one of the other things that’s really important to to think about is that the horse doesn’t really experience rain tension directly. What the horse experiences is bit pressure within the mouth.
Now pressure is is false or tension in this case divided by area of contact. Now conceivably with the double bridle you’ve actually got more contact within the mouth so that the area is greater so for the same tension it could be that the pressure is less. Now one of the other things that’s been
It’s kind of being discussed quite a lot and again, this is theory There are various groups talking about the fact that the curb is a lever bit. Yes it is But it’s a type one lever with a floating fulcrum Now some groups are claiming this is a class 2 or nutcracker type lever It’s not and there are some videos on YouTube which are flawed
showing or trying to demonstrate the action of the curved bit. This is just not correct. It’s flawed physics and it’s a class one lever. Now what also makes this slightly complicated is because the bit slightly rotates and moves within the mouth there are periods when the the bit is static and there are periods when the bit is translating or moving and rotating but
Interestingly what this tends to do is reduce the impact of the pressure on the bit. Now in terms of levers, when we talk about a class one lever, the lever actually starts from the bottom of the attachment of the curb rein and then we have the
bit itself in the mouth which is the fulcrum and then we have the top part, top section of the bit which is part of the lever. Now the actual lever is the lever effect is the bottom length to the bit divided by the top length and this tends to be about 1.5 and this is what’s called the mechanical advantage. So if you measure a force of
on the reins, the tension on the reins of 10 kilos, which is quite high. We generally only measure those for very brief periods. But if we were to measure a tension on the rein of 10 kilos, this could equate to a force of 15 kilos on the bit itself. But because of all these different complications of actually what’s happening with the bit and how the bit is positioned and moving,
actually that what we call mechanical advantage is actually reduced in the double bridle it isn’t a class two lever it isn’t a nutcracker it’s a class one lever with a floating fulcrum and we’re working with a number of other scientists who have worked in this area Dr. Graham Cross who’s been involved in bitwork quite
significantly. is a sort of mathematician and physicist and has published some great previous research. So we’ve been in contact with Graham and essentially trying to check out my physics and we’re pretty much on the same page. So what are the next steps? Well we are also as a group looking at the behavior of horses in
this study looking for behavioural indicators in the snaffle versus the double and this is going to be really exciting I can’t talk about it yet but that research hopefully will be published fairly soon. What we would really like to get at is to be able to measure pressure of the bit in the mouth directly. Now that’s really technically challenging.
But it is something that we are working on and we hope to have a working system Fairly soon. So that would be really really exciting to have that Perhaps for me, I think you know This is interesting and it’s going to upset a lot of people because most people have already decided that the double bridle is worse Whatever worse means than the snaffle bridle And this may actually not be the case
So this is going to be interesting and I think the behavioral work will really reinforce why we need to do science to answer questions rather than just come up with theories. There was one really disappointing aspect of publishing this study in that some of the people involved in reviewing or editing, we’re not really sure, tried to
sabotage publication of this paper because they didn’t agree with it. Now that is something really that shouldn’t be happening in science. I did experience this once before in my career 30 years or so ago when we published a paper or we tried to publish a paper initially showing that ATP decreased in muscle in horse muscle during exercise. Now this had not been shown in human muscle
and there were some groups in the states that wanted to try and see if they could be the first to show this when they saw when they reviewed our paper and so they blocked our paper for a long time in order to carry out their own experiments and they finally got called out and we got our work published so I’m a co-author on the first paper to show that ATP decreased in muscle during intense exercise.
I don’t think that’s the motivation here. think it’s the that this doesn’t fit certain people’s narratives around the double snaffle. There are people that have highly invested and groups that have highly invested in saying that the double is bad. Personally, people have said to me, what do you what would you rather see horses ridden in? I’d love to see horses ridden without a bit.
I think I’d love to see horses in rubber snaffles, whatever works. Now people turn around and say, well, you can’t start, you know, suddenly take a horse that’s been trained in a double and put it in a rubber snaffle or ride it, you know, bit less. Well, actually I probably agree. I think that’s quite challenging. But if you started those horses from the first time that they were put in a bridle,
or weren’t put in a bridle or with bit less or with a rubber snuffle then I think it’s probably achievable but it needs a different approach. I think it can be hard to suddenly change a horse from one thing that it’s been experiencing for 10 years. I don’t know that’s another study. We have to test these things out rather than just come up with what we think.
So I’d like to see the option given for horses to be able to be able to compete in whatever the rider wants to provided of course that it is safe and providing that of course we have no concerns that it is likely to have a negative effect on horse welfare. So we do have more papers on the way
we are working on a paper to describe what’s happening with the curb chain in particular and we have this work on the behavioural element of the study which is currently under review in the Equine Veterinary Journal and subject to funding we
say are planning to repeat or carry on a lot of this work further. So the research was funded in part by the world class performance program who actually paid for the additional pressure mats. These are really specialized very small pressure mats that we put under. They’re similar to well they are they are the same principle and type of
pressure mat that we use between the saddle and the horse but they’re just smaller versions. So in terms of who funded the work this was funded by Hartbury University Research and Knowledge Exchange Committee and the British Equestrian Federation. The paper is open access and anyone can read this and we’ll include a link to the paper below.
This is a really interesting and very fast moving area of research. I’m delighted to be working on this. I’m working with a great team of people. And as say, what I hope is that all of this research contributes to discussions around equine welfare because that has to be our priority at this time.
