How Hard Should You Exercise?
For general health, frequency is more important than intensity
Exercise is vital to your health. Regular exercise helps people with diabetes control their blood glucose, cholesterol and blood pressure;even moderate exercise can help prevent diabetes in people at risk of developing it. Of course, before you start any exercise program, you should always check with your physician.
Once you're cleared to begin, how hard should you exercise?
The most essential element in a successful exercise program is to engage in aerobic activities that you enjoy. Simply put, you need to get your heart pumping faster. While anaerobic exercise such as weightlifting, and flexibility exercises such as stretching, can increase muscle mass and make you more limber, only aerobic activity such as walking, running, swimming and riding a bike significantly increase your metabolism and produce the kind of benefits that will help control your blood glucose levels.
To realize maximal benefits you should spend time at your target heart rate. Your target heart rate is based on your age and how intensely you plan to exercise. A person who wants to exercise at moderate intensity should achieve a heart rate of 50 percent to 70 percent of their maximal heart rate, while a person who wants to exercise at vigorous intensity should reach 70 percent to 85 percent of their maximal heart rate. People typically do higher-intensity periods for a defined time (10 or 20 minutes of a 30-minute exercise period). Be sure to allow time for a warm up and cool down.
Your maximal heart rate can be estimated by subtracting your age from 220. Thus, if you are 50 years old, your maximal heart rate is 220 - 50 = 170 beats per minute (bpm). Your target heart rate for moderate exercise is 50 percent to 70 percent of this, or 85-119 bpm. Your target heart rate for vigorous intensity exercise should reach 119-145 bpm.
You can easily determine your heart rate during exercise by measuring your pulse for 10 seconds and then multiplying that number by 6. (The easiest way to take your pulse is to place two fingers on your carotid artery, which is along the outer edge of your trachea, or windpipe, in your neck. You may also wish to use one of the many inexpensive wristwatch-type heart rate monitors now on the market. Some models will even record time spent in specified heart rate ranges.) If your target heart rate is 90 bpm, for example, and your 10-second pulse is only 12, then the resulting heart rate of 72 (12 multiplied by 6) is short of your goal and you may want to exercise harder.
A much simpler, non-mathematical way to estimate if you're exercising hard enough is to use the "talk test." If you are exercising at a level where your heart is beating fast but you are just able to hold a conversation, then you're exercising at a moderate level. If your conversation is an occasional nod of the head or a one- or-two word reply, then you are exercising vigorously. At no point should you be exercising at a level where you cannot communicate even briefly with other people.
What kind of exercise is best?
There's no magic formula; every kind of aerobic activity has benefits. The important factors are the length, intensity and frequency of exercise. For example, if you can exercise only 15 minutes at a time, you may want to exert yourself more, or more often, than if you exercise for 45 minutes at a time. For general health, frequency is key. It's better to exercise at a moderate intensity for 30 to 60 minutes four or five times a week than to exercise vigorously only once a week for several hours.
Even a moderate amount of exercise has been shown to provide benefits, including lowering blood glucose. In one study, walking briskly every day for at least 30 minutes helped to lower blood glucose, blood pressure and cholesterol. The "brisk walk" used in this study was a 3-mph pace, where the participants walked quickly but comfortably enough to enjoy the walk. Their heart rate increased, but not so much that they even noticed they were "exercising." (A 3-mph pace is close to the speed a car in gear would reach if you took your foot off of the brake.)
Does more intense exercise produce greater benefits?
The more intense the exercise, the greater are the benefits overall. But, for the purposes of diabetes control and general fitness, you don't have to exercise vigorously to benefit. Remember, moderate exercise is better than little or none at all. So ride a bike or garden or ballroom dance. And, if you do decide to exercise vigorously, keep in mind that you don't need to push yourself to the breaking point to derive substantial benefits. Indeed, you should never exercise so long or so hard that you can't catch your breath at all or you feel lightheaded or sick. If you do, stop exercising immediately, check your blood glucose to see if any feelings of dizziness are signs of hypoglycemia and, if necessary, seek medical attention.
You should monitor your blood glucose levels before and after exercise, because they will tend to drop. That's a part of good diabetes management. Don't let your blood glucose levels drop too low! Because they might drop suddenly, you should keep a source of emergency glucose or carbohydrate with you when you exercise. These can include half a cup of juice, 1-2 teaspoons of honey, 5-6 pieces of hard candy, and other sources of fast-acting carbohydrate. If you start to see a pattern in which your blood glucose level drops sharply after exercise, consult your physician to determine how to continue with your exercise program in the most beneficial way.
You may feel particularly hungry after vigorous exercise. That's normal. If you're overweight and trying to lose weight, you should be cautious about overeating. But if you're at a healthy weight already, you will find that you can probably eat a more substantial meal. Whatever your circumstance, just be careful to work within the boundaries of your overall diet plan.
So what are you waiting for? It's time to start exercising.