A Natural Solution to Address Bleeding in Racehorses

I submit that we can control the instances of EIPH in the vast majority of thoroughbreds through the re-structuring of conditioning regimens and a mandatory pre-race warm up protocol.

To review, thoroughbred bleeding is principally due to high blood pressure build up in pulmonary capillaries during a race, this pressure quickly increases faster than these vessels can accommodate the increased blood flow, leading to many ruptures within the sensitive lung tissues.

Lasix is touted as our best option for prevention: it is a diuretic and removes water from blood plasma, which decreases blood volume, in turn decreasing pulmonary capillary pressures, thereby lessening or removing instances of bleeding within the lungs.

Do you really think that any drug has 100% positive characteristics, such as prevention of bleeding, without having any less than desirable side effects?

Among others the loss of electrolytes due to increased urination is of primary concern. Potassium and calcium are responsible for many cellular processes in the horse, such as maintaining a healthy bone density. Interestingly enough, these adverse effects are further exacerbated by corticosteroids. C’mon, there is no free lunch – especially where drugs are concerned. Not for humans, not for horses. Yet overweight humans continue to search for the magic pill that will help them lose weight and the US thoroughbred establishment backs the magic Lasix injection as a cure for bleeders.

So, the challenge remains to lessen EIPH without introducing negative side effects from any pharmacological ‘treatment’.  Again, the 2 root causes of EIPH :

  1. Blood pressures too high during race
  2. Capillaries burst due to sudden increased pressures and lack of necessary flexibility

My suggested remedies:

Enforce a specific warm-up regimen prior to each race. It shouldn’t have to come to this, but watching horse after horse walk/jog while their neck is wrenched towards a lead pony in the post parade is nauseating. How is 2 minutes of 10mph jogging with a heart rate of 120bpm supposed to prepare a horse’s circulatory system for an event consisting of 35+mph speeds and maximum heart rates near 230bpm?  No wonder when firing from the gate that the pulmonary capillaries are caught sleeping and cannot keep up with the demands of rapidly increasing pressures from within.

To make matters worse, when a horse is asked to pick it up to a sprinting pace, his spleen contracts and shoots up to 30% more red blood cells into the mix, further thickening the blood and the associated high blood pressures.  This is part of the ‘fight or flight’ response designed by nature to allow this animal of prey to escape his predators.

This splenic contraction needs to take place PRIOR to loading into the gate, not within the first few strides of a race. Nothing major, just a nice 1-2F in 13sec/furlong pace, finishing up with 5-7 minutes left before loading. Is your horse not behaviorally trained to pull this off without running off with the rider? Well then you have some extra work to do in the mornings until he is capable. Some will learn immediately, others will be a headache – that is the nature of the beast. He should be warming up in this manner prior to any training breeze as well for good measure.

How does this enforced warm-up address the two key causes of EIPH?
With the 30% additional red blood cells introduced into the horse’s system 5-7 minutes before post time, you are allowing millions of pulmonary capillaries quite a bit of time to adapt and stretch, a process called vasodilation. As it stands right now, that burst of blood volume is shot into the horse during the first few jumps from the gate, and he is then expected to continue for an additional 60-120 seconds at near full throttle. With a mandatory race-specific warm up, by the time a horse fires from the gate, he has had several minutes to adapt to the increased blood pressures from the splenic contraction while waiting to load.

Condition horses aerobically for longer distances. 

Currently, 99% of American horses never gallop further than 2 miles a day. Aerobic exercise is by definition achieved at an intensity of approximately 60-70% of maximum heart rate. A stakes winner may accomplish this at a 2:45 per mile pace, while a bottom level claimer may require a 4min mile pace, perhaps even a trot. Regardless, it is slow/safe speeds I am talking about – which may be boring as hell, but necessary to undertake in order to truly build a foundation for the racehorse.

As seen above one of the major problems in EIPH is the ability of the pulmonary capillaries to handle rapidly increasing blood pressures. Most readers probably think the amount of capillaries in a horse’s lungs is set by genetics. This is absolutely true, but additional aerobic training increases the number of capillaries in the lungs as well – and more capillaries equates to more pipes with which to deal with a large increase in blood pressures.

Once a horse is in the middle of a campaign, it’s too late to add significant aerobic mileage. This groundwork needs to be put in once he’s started training for the upcoming season. Don’t stop increasing distance when his gallops reach 1.5-2 miles, slow down the pace a few times each week and move up to 2.25 miles, then 2.5, etc. It should be noted that without an onboard heart rate monitor you are almost guaranteed to go too fast for optimal aerobic development as your horse, and rider, will be in a hurry to finish.

Taking Lasix away from a horse is cruel? Give me a break.

Asking a horse to sprint several 11-12sec furlongs out of the gate with zero warm-up, that is what is cruel for the horse, not the withholding of a drug designed purely to allow them to outrun their physiological warning signs. Similarly, conditioning a horse to breeze 4F in :48 then expecting him to run 8F in 1:36 isn’t very humane either, but I digress.

Simply ‘adopting the European model’ of zero tolerance on raceday drugs is not the solution. Traipsing through a half mile on turf in :52sec has very little in common with a first half mile on dirt in :46 – as some of the pressures on the lungs of a horse is undoubtedly due to the combination of being asked for higher speeds more quickly on a less forgiving surface.

All of this being said, nearly all current runners are stuck in the Furosemide cycle, and nothing you can do to a 4yo conditioned to race on Lasix his whole life is going to work wonders – these interventions are best suited to the yearlings you have going into formal training this fall. Perhaps in preparation for the possible upcoming raceday drug modifications/removals?

Compare my suggested prevention of bleeding to prevention of bone injuries in young horses. Once Dr. David Nunamaker discovered that more fast furlongs at age 2 resulted in superior bone development, the incidences of bucked shins and saucer fractures dropped dramatically. Likewise, the pulmonary capillaries of our horses need to be conditioned specifically to the task of American-style racing.

I’m no pioneer, this stuff was detailed 15+ years ago by a fellow much smarter than myself and summarily ignored by everyone:


In anticipation of a litany of possibly derisive comments to this post, I leave you with a quote from Mahatma Gandhi:

“First they ignore you, then they laugh at you, then they fight you, then you win.”

EDIT 11/28/15:

Not sure why this post suddenly became white hot after 4 years, but another post I did is also relevant to the topic, and I think a bit better:


Of course, the practical application of this piece was evident just 4 weeks ago as Runhappy won the Breeders Cup Sprint sans-Lasix, and with a plethora of race-like works under his belt (which earned the connections many naysayers).


About bpressey

Equine Exercise Physiologist

Posted on June 2, 2011, in Uncategorized. Bookmark the permalink. 9 Comments.

  1. I couldn’t agree more, Bill, and I do so hope that the excellent Gandhi quote you closed with comes true for all of us who want to see the end of race-day medication in America.

  2. Jim Culpepper

    Among my mentors was Jess Bigham who would “breeze” his racing pigeons on race day morning.

  3. Jim Culpepper

    I Forgot to mention that inbreeding to soundness should help, if soundness includes the lungs and circulatory system.

  4. Lasix in Horse Racing is NOT sustainable. Owners and trainers complaining about lasix ban need to spend more time finding alternative methods and medicines and less time crying. Adapting to outside forces and rules is something that all business and industry must deal with. Get with the program horsemen.

    • I agree. IMO you can race all the cheap horses that you wish to filled to the gills with Lasix – but you cannot expect to do that with graded stakes winners who will then head to stud and produce thousands of chemically dependent offspring – and not pay the piper a few generations down the road. Its a fact that starts/year is HALF of what it was pre-Lasix, granted there are other factors involved, but back in the 80s vets told us that Lasix would give us more starts, not less.

      Plus the current political environment is towards drug-free racing, you can fight it all you wish…but you better start to plan for the days where conditioning horses is not possible via syringe. Half of these owners/trainers/breeders/vets are obese at age 40 and will spend the next 4 decades taking pills for hypertension, diabetes, and other related conditions, of course they want to address EIPH via drugs as well.

  5. I found an article online about 6 years ago (pretty sure is was from Hong Kong Jockey Club) how they had done testing and warming up properly does indeed waylay bleeding episodes. I wish I had saved the article……….I have looked for it many times, but could never find it.

  6. I have had many fast warm ups or slow breezes during the post parades with much success. Now you have less area to do these things . We had ponies to use with the horses during this also. Some years ago we could do it.

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