What should my heart rate be during exercise?

Q. What should my heart rate be during exercise?

Richard Weil, MEd, CDE, recommends calculating your target heart rate with a formula called the "heart rate reserve" method. Use a watch with a second hand to keep track of how many times your heart beats per minute. You can feel your heartbeat at the underside of your wrist or along the side of your neck.

Here's how to use the formula:

* Determine your Maximum Heart Rate (MHR) by subtracting your age from 220.
* Then, subtract your resting heart rate (it's best to take this when you first wake up in the morning) from your Maximum Heart Rate to find your Heart Rate Reserve (HRR).
* Multiply your HRR by the percentage of your MHR at which you wish to train (60% to 85% is the usual range for people looking to increase fitness and health).
* Add your resting heart rate back to that result to get your target rate.

So, assuming an age of 27, a resting heart rate of 70 beats per minute, and a desired training range of 70%, the calculation would look like this:

220 - 27 = 193
193 - 70 = 123
123 x .70% = 86
86 + 70 = 156

Remember, this is an estimate, not an absolute. Also keep in mind that athletes may exceed the training zone, and even the maximum heart rate, during high-intensity training.

Q. My weight has hit a plateau. What do I do?

There are several reasons why your weight can hit a plateau, including:

* Losing weight too quickly. When this happens, your metabolism (the rate at which your body burns calories) can slow down because your body senses it is starving. Rapid or large amounts of weight loss can slow your metabolism by as much as 40% in six months.
* Losing muscle. When you lose weight, up to 25% can come from muscle tissue. And since muscle is the engine in your body that burns calories and helps maintain your metabolism, losing it can hinder weight loss. Weightlifting can help preserve and build muscle.
* Reaching your body's particular set point -- the weight and metabolic rate your body is genetically programmed to be. Once you reach that point, it's much harder to lose weight and even if you do, you're likely to regain it. If you're at a weight at which you've hit a plateau in the past, if your body generally seems to gravitate toward that weight, and you're within a BMI (body-mass index) range of 20 to 25, then you may be at your set point.
* Decreasing your physical activity and/or increasing your caloric intake. People lose weight all the time by reducing their caloric intake without doing any exercise, but it's almost impossible to keep weight off without exercising. Many scientists agree that physical activity is the single best predictor of whether a person will maintain a weight loss.
* Other health factors, including thyroid or adrenal gland problems; medications like antidepressants; quitting smoking; menopause; and pregnancy.

Even with any of the above factors, the bottom line to losing weight is eating fewer calories than you burn. Studies show that people almost always underestimate how many calories they're eating. So if you're struggling with weight loss, you're still exercising, and you've ruled out any of the above reasons for weight plateaus, look at your calorie intake.

As for exercise and weight plateaus, sometimes a change in routine can help. Instead of the treadmill, try the bike, or the stepper. Instead of a dance class, try a stretch and tone class. If you're not weight lifting, this would be a good time to start. If you already do aerobic exercise, try adding intervals (short bursts of higher-intensity exercise) to your aerobic workouts. And keep reminding yourself that if you maintain an active lifestyle and continue with healthy eating, you will reach your goals.