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Whether he's headed for a demanding cross-country course, an endurance ride or a hunter pace, your horse faces a challenge. Will he finish the ride with energy to spare? Or will he tire quickly or, worse, finish so drained by the effort that you have to scratch him from the event?
Your horse's heart will play a big role in determining the answers to those questions. It's an incredible athletic machine, and he can't reach his -potential unless it's well tuned. This article will explain why the heart is so important and how you can ensure it performs at its best.
Hearts Matter
The heart is the key to performance because, along with the blood vessels and the lungs, it delivers oxygen and fuel to working muscles. Like an internal combustion engine, your horse's muscles use the oxygen to burn the fuel--fatty acids and blood glucose--releasing energy for contraction. This aerobic (with oxygen) system is super-efficient, and it constantly adapts to meet the demands of the moment. When your horse's brain senses that the muscles need more oxygen, for example, it orders the heart and lungs to work harder. Respiration and heart rates increase to speed delivery of oxygen, and blood vessels dilate or contract to change patterns of blood flow.
A horse's heart rate can go from as low as 25 beats per minute (bpm) at rest to 10 times that at peak exertion--a far greater range than even the most elite human athletes can achieve. But if the muscles work hard enough, their needs outstrip the ability of the cardiovascular system to deliver. Then the horse switches to anaerobic (without oxygen) energy production, using muscle enzymes to burn glycogen and other fuels stored in muscle tissue. This method is much less efficient, and the horse can keep it up for only a few minutes before his muscles tire.
Cardiovascular fitness changes the equation. Like any muscle, the heart gets stronger with use, so hard work makes it stronger and more efficient. It can beat faster for longer periods of time, and its stroke volume--the amount of blood pushed out with each beat--increases. A fit horse also makes more oxygen-carrying red blood cells and clears old, spent red cells from his blood more quickly. New capillaries (tiny blood vessels) develop in the muscles and in the lungs, speeding the exchange of oxygen and carbon dioxide. He's able to do more before switching to the anaerobic system, and he recovers faster after exercise. Increased blood flow also delivers nutrients and has healthy effects throughout the body, from a shiny coat to healthy hooves.
Conditioning work increases your horse's aerobic capacity by strategically upping the demands on the oxygen delivery system. These changes take place slowly. To reach the level of fitness your horse needs for competition, you need to do the right amount of work, at the right level, over time. Too little, and he won't be up to the demands of the event; too much, and he'll be tired, stressed and possibly injured. How can you gauge if you're on target? Monitor his heart rate.
Know His Rates
Start by getting familiar with your horse's normal heart rates. You can use a stethoscope (inexpensive ones sell for less than $10) and a watch with a second hand. Listen along the heart-girth, behind the left elbow. (You may need to experiment a bit until you find a good listening spot.) Count beats for 15 seconds, and multiply by four to find the rate in bpm. Measure the rate in these situations:
At rest: Your horse's heart may laze along at around 25 or 30 bpm when he's just hanging out in his stall, but you're more likely to get a resting reading of 40 to 50 at first. That's because just by entering his stall and putting the stethoscope on his side, you'll cause the rate to go up. If you do this often, though, he won't be so interested. You'll find that you get lower readings.
The resting heart rate is a useful measure of health. Take resting readings at the same time of day for several days, and calculate the average. A marked departure from the average rate (an increase from 30 bpm to 50, say) can signal illness or some other type of stress.
After exercise: Check your horse's rate immediately after exercise and then at five-minute intervals to see how quickly he recovers. The readings you get will depend on how hard he worked, how fit he is and other factors (more on this later). Even after a cross-country gallop, though, you want to see the rate down around 100 bpm within five minutes and in the 50 to 60 bpm range within 30 minutes.
