"There are many different things that happen when a horse is warmed up," says Brian Nielsen, PhD, associate professor and researcher in equine exercise physiology and nutrition at Michigan State University. "The warm-up gets the heart rate going from a resting state. This can occur nearly instantaneously, such as when the horse shies, but scaring a horse isn't exactly how you'd want to go about getting things started.
"Also during warm-up the horse's spleen contracts, and this releases red blood cells, which are responsible for transporting oxygen," Nielsen continues. "More red cells mean an increased oxygen-carrying capacity. The more oxygen the animal can carry, the better the performance. Horses are unique in their ability to store red blood cells in the spleen. When horses exercise, the packed cell volume (PCV, the amount of red blood cells in a blood sample) can jump up to 70%."
This splenic contraction aids in the inborn "fight-or-flight" survival response so that the horse can sprint away from danger and sustain his speed for a long period of time.
To put it into perspective, let's look at this from the human point of view. In cycling, one of the biggest controversies in the sport has been the issue of blood doping. Humans can't store red blood cells in their spleens like horses, and a human athlete's PCV will not change much whether he is at rest or exercising.
"Human athletes therefore have been known to increase red blood cells in their bloodstream by harvesting their own red blood cells and freezing them," says Nielsen. "They then transfuse the cells prior to competition and so increase the oxygen-carrying capacity."
For horses, the warm-up naturally taps into this readily available source. By warming up, the release of red blood cells is complete, and they are fairly well distributed in circulation. You shouldn't be dependent on the splenic contraction to occur at the start of exercise, because there is a little bit of lag time between the start of exercise and when the contraction occurs and the red blood cells are distributed uniformly in the blood.
Body Temperature Alteration
The warm-up also increases the horse's muscle temperature. "When we exercise," says Nielsen, "we use different fuels within the body, such as glycogen and glucose. When they are utilized, heat is also generated, which can raise the body temperature. Certain enzymes in muscles work better at higher temperatures. However, if the core (body) temperature gets too high, the body will shut down. Small increases in temperature of the muscle will allow for the enzymes in the muscles to work efficiently."
Another benefit is that the hemoglobin (the iron-containing pigment in red blood cells) functions in oxygen transport more readily at higher temperatures within the muscles.
Energy stored in the muscle in the form of glycogen is used the most during the initial stage of exercise. Humans and horses are the same in this respect. There is only so much glycogen stored in the muscle, and if none of the other warm-up benefits we mentioned earlier have begun, the muscle fibers use glycogen for energy first.
"You want to minimize how much muscle glycogen you use right away," says Nielsen. "If you don't warm up to enhance the usage of glucose in the blood, you'll run out of gas quickly. You want to warm up gradually so the circulatory system can adjust. Warming up slowly gets the glucose into the blood and saves the glycogen, which is an easy energy to get to, so you want to save it for as long as possible."
Every stride a horse takes impacts the tendons. When a horse takes strides during the warm-up process, the collagen molecules in tendons pack together and water is redistributed within the matrix, decreasing the tendons' stiffness.
"Warming up allows the tendon to stretch to a greater degree without injury," explains Nielsen.
Warming up also increases muscle strength. In human weight lifting, the athlete is able to lift more weight after the first repetition. Likewise, a horse's muscle contraction strength is increased by virtue of stretching out during the warm-up stage.
The best method of warming up is unclear. In the past, trainers and riders have adapted warm-up techniques from tradition or industry standards rather than scientific fact. But this is mainly because there has been little scientific data on the equine warm-up. More research has been done with human athletes, but even scientists in that field aren't exactly sure what technique is best.
Catherine Kohn, VMD, PhD, Dipl. ACVIM, professor in the Department of Veterinary Clinical Sciences at The Ohio State University's College of Veterinary Medicine, is conducting a new study on how riders are choosing to warm up for eventing's new short format.
New rules removed the traditional roads and tracks and steeplechase phases from the speed and endurance test of the competition, leaving only cross country.
Says Kohn, "Riders feel the need to replace these traditional phases of the event with a warm-up that will prepare horses mentally and physically for the demanding cross country test. There is good evidence from a few studies on horses that warm-up can improve performance."
Treadmill studies simulating racing (Geor 2000, McCutcheon 1999) showed that oxygen uptake could be accelerated and increased by warm-up prior to the criterion exercise, and time to fatigue was prolonged. The effects on oxygen uptake were transient, and abated within 10 minutes of completing the warm-up.
The optimum warm-up formula for equine athletes most likely will vary with their particular disciplines--components might be similar, but the recipe should be specific for the sport.
What method works best for horses competing in the new eventing short format remains to be seen.
In her observations, Kohn has noted a change in warm-ups over the past two years since the format was altered. Early on, many riders felt they needed to include a substantial gallop on the day of competition in their warm-up.
The results of a rider survey at Fair Hill CCI*** in Maryland in 2004 showed that more than half of the riders on cross country employed a fast warm-up, with some variation of walk, trot, and gallop.
"The total gallop time was around three minutes," she says. "But there was quite a big range. Some galloped up a slight slope, others didn't. The first warm-up lasted on average 25 minutes. Then competitors rested the horses for a couple of hours and then conducted a second warm-up 30 minutes or so before cross country."
Kohn repeated her survey at three additional competitions. Although all the data have not yet been analyzed, the trend is for fewer competitors to choose to gallop about two hours before the cross- country test. In fact, she says that CCI*** and CCI**** warm-ups now often resemble horse trial warm-ups (CCI events generally are performed over three days, while horse trials lack roads and tracks and occur over one or two days).
"Forty-five minutes to an hour or so before the cross country test, riders will walk, trot, and canter, and possibly include a short gallop (one minute or less)," she says. "They jump a few fences. Some riders will then get off the horse for a few minutes to allow the horse's heart rate to decrease and the respiratory rate to return to normal. Some riders sponge the horse off. These activities simulate the recovery procedures we used in the 10-minute box after the first three phases of a classic format CCI. Other riders may choose to stay on their horses after the warm-up, walking quietly until their start times.
"We do have more experience with the short form of eventing now, and things are changing, but we've yet to define the optimum warm up," she continues. "There are so many variables that it's very difficult to correlate type of warm-up to outcome. The outcome on the cross country is influenced by many variables, such as the horse's ability to run and jump and the rider's expertise: There is a huge difference between me riding the horse and (Olympian) Phillip Dutton riding it, for instance. Without a very complex study, it's going to be very hard to determine how warm-up techniques impact performance."
Ultimately the type of warm-up is the rider's choice because he or she knows the horse best.
"You have to trust your experience," says Nielsen. "It varies so much between horses and between disciplines. One horse might only need a walk, trot, and canter to get the physical benefit, where others might need more to get their minds focused on the task at hand. Knowing your horse is important, and (so is) realizing that warming up is both a mental and physical task."
GOLDEN RULE OF WARMUP
Although the best method of warm-up might be subject for discussion, there are some hard and fast rules regarding prior exercise:
- Warming up for too long saps energy reserves that should be saved for competition.
- Warm up smart: An out-of-breath horse likely has used up energy reserves of glycogen that would have been best reserved for competition.
- Avoid overheating the horse. If the horse is too hot, its system will shut down.
- The oxygen delivery system must be prepped for peak performance. This effect can be lost if the interval between warm-up and competition is too long (more than 10-12 minutes).
- Warm up the tendons and muscles to avoid injuries.
- Make sure the horse is mentally prepared and focused.--Sharon Biggs
About the Author
Sharon Biggs Waller is a freelance writer for equine science and human interest publications. Her work has appeared in several publications and on several websites, and she is a classical dressage instructor.
POLL: University Equine Hospitals