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JUNE 2006 • VOLUME 10 • ©HORSES For LIFE™ Magazine
In this issue of Horses For LIFE we have tried to bring together in one place the current information on this subject of rollkur/hyperflexion from various resources. We would be remiss if didn't include a brief synopsis of our three articles in the November and December Issues on Breathing and the Position of the Head. Please feel free to go back and reread the entire articles. 
FROM NOVEMBER 2005 • VOLUME 3 • HORSES For LIFE™ Magazine In resting horses, the air entering the upper airway must turn approximately 90º to flow from the nasal passage into the trachea. That change in direction of airflow contributes to the work of breathing [Petsche et al]. During exercise, the effort needed to change airflow direction is reduced by straightening of the upper airway [Petsche et al]. Straightening not only allows air a more direct route to and from the lung, it also tends to stretch and stiffen upper airway tissues, making them more rigid and more resistant to collapse.” Derksen et al
This study demonstrated for the first time that head and neck position affects upper airway mechanics in exercising horses.
FROM DECEMBER 2005 • VOLUME 4 • HORSES For LIFE™ Magazine
A follow-up article on Horses Not Breathing Your questions asked and answered by the researcher!
Special Thanks to Dr. Derksen to take the time out of his busy schedule to answer our questions directly. What I do think is key here, is not that there is any tension in the horses neck causing a collapse. Rather that actually might be the problem that without tension the trachea is more prone to collapse. Being a soft tissue structure that it relies upon other muscle and tissue to help support it when increased exertion requires additional airflow. "Straightening not only allows air a more direct route to and from the lung, it also tends to stretch and stiffen upper airway tissues, making them more rigid and more resistant to collapse." Derksen et al I think it is important to note that this was not a static collapse but a dynamic collapse. Meaning that there was no problem breathing out, just breathing in. If this was problem because of existing tension, for example putting pressure on the trachea, then we would expect this to be a static collapse with problems both on inhalation and exhalation.
" The fact that you would have more of a problem during inhaling would make sense as this phase would be more prone to cause instability or collapse of the airway. " I must admit that it took me awhile to wrap my head around this. How it was the actual force of the lungs trying to inhale that was causing the problems I kept wanting to imagine something pushing on the trachea that was causing the problems. " So as the throat of the horse is constricted you get complicated variations in pressure that tend to cause the surrounding tissue (which is quite flexible after all) to move around and take up less efficient shapes." Absolutely. The study by Petsche was on healthy horses with no known breathing problems. All the horses had problems inhaling when put into a flexed position. I think it is important to note that they picked healthy horses. "These horses had no history of airway obstruction and no abnormalities detected by physical examination and airway endoscopy." We know that for a horse at rest that is breathing 20 times a minute with a tidal volume of 5 liters has a minute ventilation of 5 liters. As this horse begins to exercise, respiratory rate and tidal volume increase to achieve a minute ventilation of approximately 1,500 liters/minute. The upper airway must accommodate this large increase in airflow by undergoing changes in caliber, rigidity, and shape. So when exactly does this become a problem? "In the resting horse, pressure changes are relatively modest and therefore changes in resistance are also small. On exhalation, there is positive pressure in the upper airway moving air out to atmosphere. This positive pressure tends to dilate the upper airway, thereby decreasing resistance. Conversely, on inhalation, there is a negative pressure in the upper airway, relative to atmosphere. This is needed to move air in from the atmosphere via the upper airways into the lungs. This negative pressure tends to decrease airway caliber, thereby increasing resistance. During exercise, these pressure swings are greatly exaggerated because of the much higher airflows." Derksen et al The research noted a 50% decrease in airflow in when the horse was on the vertical. The question then became what would happen if you went behind the vertical?
Dr Derksen has been interested for some time in doing a study on dressage horses and rollkur. ----------
What is difficult about this kind of research is that unless you bring a lot of people's attention to it, there is no drive to extend the research parameters any further. To test, if there are parameters in which this will not occur. Maybe this article can be part of that, I don't know. This is where we need additional research. And for people to ask for and fund this research. "It has been postulated that upper airway impedance is reduced when the head and neck are extended and that upper airway impedance is increased when the neck is flexed and the head is in a tucked position (Cook 1981)." Veterinarians have known of this There is also some suggestion that airway obstruction exhausts diaphragmatic vasoldilator reserve. I would suggest that this is also another area that requires further research. This might also provide us with an additional diagnostic tool to see if this was affecting our own horses.
I have a feeling that if everyone truly rode according to the old classical mantra's of head ahead of the vertical and only approaching the vertical on piaffe and not setting the head; and developing the back end carriage, topline stretch and then allowed the head hang like a chandelier. The masters often knew what they were doing. Many have known of this problem, as it becomes more obvious if another problem already existing problem is present. The good part of that answer in my mind is that if even a small increase would make a huge decrease in the ability to breathe for the horse, that a small decrease would make a huge increase in the ability to breathe. Thus, coming even a little ahead of the vertical should improve the horse's ability to breathe. Let's go back to our classical heritage and help our horses. ------------------------------------------------------------------------------------------------------------- Contributors:
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June 2006 • Volume 10 HORSES FOR LIFE™ Please note all resources presented are © copyright protected by the original owners and reprinted with permission OR © Copyright Horses For Life™ 2005 to 2006 Please write to us! We would love to add your voice. Write to us on our contact page or email your letter to the editor directly at letters@horsesforlife.com
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Who is more at risk?? You might be surprised to find out. The dressage horse, the race horse, the jumper, the reining horse?
we went straight to the horse's mouth so to speak and spoke directly with one of the researcher's on the phone on the findings of the study. While further research is indicated, and the researchers are interested in doing that research, all indications are - that these horse's would have very real problems breathing. Help the researchers fund further research 
The answer: EVEN a small increase would make a big difference. So, for example, if you double the bend you would MORE THAN double the resistance. 
phenomenon for many years, decades even, it wasn't until the study was down by Petsche and Derksen in 1995, that this was taken into an actual scientific study. While some riders and trainers may not need further documentation, we know that those that follow rollkur do! Insisting that they do no damage to their horses... this study shows that this is just not true. Since we know that it is the amount of bend in the trachea that causes the resistance to the inflow of air causing the dynamic collapse, and we know that increasing the bend even a little will greatly exaberate the problem, this being simple mechanics, we know that these horse's are suffering. But some are not listening and we need the documentation that further study can provide.
