The idea for this column came from a quote in Mark Rashid's book A Good Horse Is Never a Bad Color (which I highly recommend) and from reading an email thread where a runner suggested that conditioning a horse is similar to conditioning a runner. Rashid was making the point that horses evolved as prey animals and thus react to the world very differently from us. Therefore, to understand the horse and its physiology we must try to consider the world from the horse's viewpoint as an evolving prey animal whose survival instinct is to run first and then figure out what's up.

With this in mind, I hypothesize that in conditioning and competing our horses, we should strive to understand horse physiology, and how it differs from human physiology. We must shape our conditioning and riding based on our understanding of equine physiology. So let's consider some of the ways equine physiology is quite different from human physiology and the implications.

Caveat: Note that I am neither an equine physiologist nor a veterinarian. The purpose of this column is to motivate you to think about conditioning and riding your horse based on a deeper understanding of the horse, not to give definitive information about horse physiology.

Do you run on middle fingers?

From the knee down on the horse's leg is equivalent to the hand in a person, i.e., the knee joint is equivalent anatomically to our wrist, the fetlock down is equivalent to the middle finger, the hoof is equivalent to our fingernail, etc. So the horse in proportion to its size has a very small structural support that takes tremendous stress.

Moreover, the horse has mainly tendons and ligaments rather than muscle in this lower structure that form a natural suspension system that can contract tremendously on impact and spring back with every stride at a trot or gallop. The good news is this gives the horse very efficient movement over good terrain. The bad news is the tremendous stress placed on these delicate structures can readily lead to stress-related-injury and lameness.

So a horse can trot almost effortlessly mile after mile on solid adobe soil or on good well-packed but not too hard dirt roads. On the other hand, when a horse is trying to go through sand or deep mud, the suspension system does not help much and the horse must "muscle" his way through the terrain. The other extreme is when the horse is going on really hard surfaces such as pavement or a dry hard-packed gravel road where the horse receives tremendous concussion.

Implications:

1. Given the tremendous stress on these structures, we must do all we can to provide the best possible balance and support through proper hoof care and shoeing. Find the best farrier you can.

2. Deep sand and mud are even tougher on horses than on people (relatively). Adjust your pace accordingly. Your horse is working hard.

Do you get fat & hairy for winter?

Horses have several mechanisms to conserve heat in the winter. They grow long coats, frequently put on extra fat if given the opportunity, and their surface capillary system contracts so there is less blood flow near the surface. By contrast, in the summer they have thin coats, their capillary system has expanded to be near the surface, and they frequently carry less weight.

This adaptation to winter is great for conserving heat, but not good for shedding heat. So even if we clip a horse and bring the horse into a winter or spring ride with no extra weight, the horse is still not able to cool with the same effectiveness as in the summer. Thus spring rides which may experience warm weather, such as the Biltmore in May in North Carolina, can be very challenging for horses.

Implication: The rider may need to slow the pace and use far more water to cool the horse on a warm winter or spring ride than on the same ride in the summer or early fall.

Were you made to run?

Horses have an incredible ability to oxygenate tissues. Horses evolved into an animal that could take a deep breath and immediately run several miles. They have an incredible cardiac output, where cardiac output is the pulse times the stroke volume. The equine stroke volume at rest is about eight times the capacity of a human heart, and that stroke volume can increase commensurately at work.

Moreover a horse's resting pulse rate is typically 25 to 40 bpm and that can increase to around 230 beats per minute under work. By contrast most humans have a resting rate of 60 to 80. A maximum heart rate for a 40-year-old human is around 180. So the ratio between at rest and maximal beats per minute for a horse is close to eight while for a human it is more like three.

On the other hand, conditioned human athletes can significantly reduce their resting pulse, while available evidence suggests conditioning horses does little to reduce the horse's resting pulse rate.

And while some humans have engaged in a controversial practice called blood doping (where they withdraw their own blood, concentrate the red blood cells and then have a transfusion just before a competition to boost their red blood cell count and aerobic capacity), Mother Nature provided the horse with a natural blood doping mechanism. The horse stores half of its red blood cells in its spleen and only releases them when needed, e.g., when the flight reflex kicks in.

Also, research done for the 1996 Olympics showed that a horse could exercise at close to maximal exertion levels with the high build-up of lactic acid for eight to 10 minutes (enough time to put a lot of distance between the horse and almost all predators) whereas humans can only do this for about a minute (think of a 400 meter race). So the horse has a far superior ability to oxygenate tissue than humans.

Implications:

1. Metabolically horses can do high performance work, e.g., flee from predators, long before they are ready structurally to do many miles of competition. And their cardiovascular condition can be improved relatively quickly. On the other hand it takes many, many months and probably years to condition the ligaments, tendons, bones, etc. So the wise rider will condition the supporting structures for many, many months or years before concentrating on cardiovascular conditioning.

2. Horses do not naturally have a sense of pace. The horse's instinct is to flee danger quickly. This can be your biggest problem at the start of a ride as the horse will want to "run with the herd" to flee danger and his hormonal system encourages him to do that. The horse can easily build up a "debt," i.e., lactic acid build-up and/or glycogen depletion, that will adversely affect performance down the trail. The rider must figure out how to channel and conserve this energy.

3. Horses may need far less conditioning in proportion to miles in competition than humans but horses need far more rest. In discussing this with Dr. Ann Stuart, assistant chef d'equipe for the U.S. team to the world championship, anecdotal evidence supports this view. However there are no definitive studies to date.

A rule of thumb for a marathoner is a minimum of two to three times the marathon distance in training each week and top runners may do far more. By contrast many 100 mile riders whose horses compete at the top level may only do 20 miles or so of serious conditioning a week, assuming the horse is free to run in a large pasture. And given the structural design of the horse, saving many of the miles for competition makes sense.

Can your horse puke?

My veterinarian has on her car a bumper sticker saying, "Ride 'til you puke," since she puked on many of the rocks going up to Sherman's Gap on the Old Dominion. However horses cannot puke as their digestive system is very different from ours. In fact they have neither the reflex reaction to trigger vomiting nor the muscle contractions to do so.

The horse has a relatively small stomach that is designed to take in repeated small meals of roughage and within 45 minutes to shift the food into a huge fermentation vat full of fluids called the intestinal system. In fact, horses at pasture spend much of their time continuously grazing. By contrast humans have a relatively large stomach designed to have a few (relatively) large meals a day. Again this is the difference between a grazing species and a hunter/gatherer. Also, horses cannot vomit and get rid of bad food and that large fermentation vat is subject to colic if thrown out of balance.

Furthermore, horses have the capability to transfer large amounts of fluid from the intestinal system into the circulatory system when needed for exercise, i.e., during flight. When the flight is over, the fluid returns to the intestines.

Now think about our sport, where rather than a flight of a few minutes we ask the horse to exercise for hours and take just a few short breaks.

Implications:

1. Horses need lots of small meals. Take advantage of checkpoints on rides. And on long loops give your horse a chance to graze or get a snack.

2. Proper hydration is critical to avoid colic problems. Read prior Endurance News education columns on how to keep your horse hydrated before, during, and after a competition.

Concepts to remember

What are the major takeaways? We need to start our consideration for conditioning with the horse's physiology--not our own. While this seems simple, you should "beware" since our understanding of the relationship between conditioning the endurance horse and equine physiology is still developing. Therefore we need to "listen" to our horses, i.e., carefully observe all of the signs they provide us and adjust our conditioning and our competition riding accordingly.

An ancillary thought is to be on the lookout for good research results: fairly well-controlled studies of conditioning and near-term and long-term results in rides. As of right now, we just don't know enough to be certain. And what works great for one type of horse might not work at all for another. Be careful. Share your knowledge and ideas with others so we all become better partners for our horses.