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all created equal, but not all the same

July 14, 2011

We may have all been endowed by our creator with certain unalienable rights, but we were not all endowed with the same maximum heart rate.

When designing a training program, by yourself or with a trainer, it’s important to remember that many of the formulas used by the health and fitness community do not apply equally to everyone. In fact, they often more accurately apply to men than to women.

Take the idea of maximum heart rate. You know how the cardio equipment at the gym has that little chart on it that tells you what, based on your age, your %85 percent and %65 of max heart rate should be? Your maximum heart rate is the highest it can safely go during exercise. During a high intensity cardio workout, exercisers generally aim for about %85 of max heart rate with intervals that may take you up as high as %90. Low intensity exercise aims for about %65 – %75. The higher intensity zones are used to challenge and expand cardio capacity; the lower one to build endurance.

Max heart rate is usually calculated by subtracting your age from 220. But last summer, scientists realized this number works for men much better than it does women. A woman’s maximum heart rate is better calculated using the formula 206 minus %88 percent of age. This significantly changes your %65 and %85 targets.

Another fitness formula that should be reconsidered is the old eight glasses of water a day rule. According to Jane Brody, a health writer at the New York Times, a more specific determination can be made based on your size:

To calculate how much water you need each day, multiply your weight in pounds by 0.08; the result is your requirement in eight-ounce cups. Before those who weigh 200 pounds panic about having to drink 16 cups of liquid a day, keep in mind that about half the fluid people need comes from fruits, vegetables and other solid foods.

The Mayo Clinic offers three different approaches to determining how much water you should drink, and About.com’s nutrition page takes you through 9 questions about things like how much you exercise, how much alcohol you drink, whether you are pregnant, and how dry the weather is.

Though Brody recommends you not rely simply on thirst to guide your water consumption, you can rely more on your body’s signals than you think.  The problem is many of us do not know what thirst really feels like. It turns out, for example, that a lot of the time when you think you are hungry you are actually thirsty. Thirst can also manifest as a headache or chapped lips. My advice is to try drinking water in response to all of these feelings. If the problem is solved, you’ll have learned that that is sometimes what thirst feels like.

When it comes to heart rate, you also have to learn to read your body’s signals. If you’ve been working out for a while, the target zones on the chart may feel easy to you. If you have not, you may really feel like you can’t get above %65 even using the woman’s formula. Trust that, and remind yourself that every body really is very different. It takes a long time and a lot of work to change your capacity, and that capacity is based on a wide variety of factors to begin with. As the machines also helpfully warn you, you’ll know you’re in trouble if you get dizzy or faint. If your skin begins to feel oddly cold, you know you have overheated. Muscle cramps also indicate that your body is not getting blood to and from the muscles efficiently enough, which means you should let your heart rate come down a little until it can. If any of these things happen, slow down or stop.

And drink water.

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