Sunday, June 29, 2008

Understanding Heart Rate


Before looking at heart rate monitors specifically, let’s delve a bit further into heart rate in general. There are many good reasons to use your heart rate as the guiding force in your running, but doing so has drawbacks as well.
Training by heart rate is good because if you know what numbers to use, there’s no more accurate way to gauge your running. When you head out for a run around your neighborhood, how do you know what your pace is? Even if you compare your splits along the way to what you usually run, who’s to say that you know what the earlier times mean? If the terrain is hilly, or the weather is warm, or you’ve been fighting a cold, or you got a bad night’s sleep, your pace from day to day will be affected. Heart-rate training proponents like to point out that heart rate monitors take all of those factors into account, and they do so in a way that helps you to progress in your training with less risk of injury and burnout.
The theory is that your heart rate can reach two extremes: your resting heart rate and your maximal heart rate.
Generally, your resting heart rate decreases as you become fitter because as your heart becomes stronger, it doesn’t have to work as hard to pump the blood that your body needs when you’re sitting around or sleeping. The average American has a resting heart rate of 72. Aerobically fit people usually have heart rates of around 60, and some hard-core distance runners have pulses of 40 or lower.
Your maximal heart rate is the highest rate that your heart can reach. Unlike your resting heart rate, it doesn’t change as you become fitter. Your maximal heart rate is set at birth. Past the age of 30, it decreases by about one beat each year, although it doesn’t decline as rapidly in very fit people. Most beginners should run at about 60 to 70 percent of their maximal heart rate. In that range, you’re going fast enough to get the benefits, but not so fast that you’re continually out of breath and running so hard that you’re more likely to get frustrated or injured. In that range, exercise should feel good.
Your resting heart rate and how hard you have to work to run in the 60 percent to 70 percent range vary from day to day. Heat, hills, stress from work, lingering fatigue from a few bad nights of sleep, dehydration, caffeine—all of these factors can elevate your heart rate. What this means is that if you monitor your training by your running pace, then maintaining that pace is going to be harder from one day to the next. If it’s 50 degrees outside and you’ve spent a restful day with the Sunday paper and you run on a flat course, your nine-minute miles are going to feel a lot easier than if it’s a hot Wednesday, and the office was miserable, and you started your day with three cups of coffee, and you’re running a hilly course.
Heart rate monitors allow for these differences. In a sense, your heart doesn’t care about all that stuff that happened today at the office. It just wants to be worked at a level of effort that’s between 60 percent and 70 percent of its maximum. That’s going to mean running slower after that stressful day at the office than on that blissful Sunday. No big deal—you’ve achieved the same aerobic benefits from both runs. Probably the biggest benefit of heart rate monitors for most runners is that they can help you to keep from working too hard. Sure, you can use monitors to help you stay above that moderate 70 percent-of-max threshold, and many serious racers use them just for that. But recreational runners can use them for the opposite end to great benefit. Using a heart rate monitor can prevent you from overdoing it so that you can continue to progress in your training. Remember, consistent, moderate running is the key to progressing, not intermittent hard bouts of exercise that leave you frazzled and possibly hurt.

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