DEAR DR. DONOHUE: Will you please answer a couple of exercise questions I’m having a hard time finding answers to? Even the instructors at my gym don’t agree with each other.

How do I know if I’m exercising as hard as I should? Do you burn more fat when you exercise less hard? — J.W.

ANSWER: Exercise benefits are proportional (to a point) to the intensity, frequency and amount of time spent exercising.

For aerobic exercise — jogging, walking, swimming, running, biking — a rough guide to intensity comes from how fast your heart beats. Age plays a very important role in determining heart rate. Untrained exercisers and people older than 50 must approach this cautiously and have the approval of their doctors.

Subtract your age from 220. The result is your maximum heart rate. During aerobic exercise, raising your heartbeat to a level that’s between 55 percent to 69 percent of your maximum rate is considered moderate-intensity exercise. Raising it to 70 percent to 85 percent is hard exercise. Hard exercise is unsafe for older people unless they have been examined by their doctors and have approval to perform it.

For strengthening exercise, choose a weight you can lift eight times comfortably. When you are able to perform three sets of eight lifts, with three minutes of rest between sets, add another repetition to your routine. When you can lift the weight 12 times for three sets, add more weight and drop back to eight consecutive lifts.

The fat question is difficult to answer. Fat burning is at its greatest when performing aerobic exercise at a level that is 70 percent to 80 percent of your calculated maximum heart rate. If the heart rate reaches 90 percent, fat burning declines.

DEAR DR. DONOHUE: I didn’t understand something you wrote about walking. You said, “Initiate the step by pushing off with the toes, and end it by landing on the heels.”

From what I have read, you’re supposed to step heel down first and not toe down. — S.S.

ANSWER: Yes, you’re right, and that’s what I was trying to say.

Land the foot on the ground with the heel. Raise the foot off the ground by pushing off with the toes.

DEAR DR. DONOHUE: In your discussion about strengthening the abdominal muscles, there were no indications of how many repetitions would be normal, or how often they should be done per day or per week. Please clarify this for me. I need such strengthening, even at 83. I promise not to overdo it. — C.L.

ANSWER: Do the number of sit-ups that you can comfortably perform. If it’s five, that enough for you. Take a rest and repeat. If you’re up to doing such exercise twice a day, that’s fine.

Three days a week is plenty.

I hope you’re not doing these exercises to get rid of abdominal fat. Fat isn’t burned by performing an exercise where fat is deposited. Fat burning takes place in all the body’s fat depots. Strengthening the abdominal muscles helps keep abdominal organs from protruding.

DEAR DR. DONOHUE: I am a 95-year-old male and have tried to be physically active. I walk every day, lift light weights, lap swim three times a week and ride a stationary bike. I have been given a clean bill of health. I find it increasingly difficult to keep up this regimen. Am I overdoing? Should I back off? — S.B.

ANSWER: If it feels to you that you’re overdoing, you are overdoing. You can back off and still retain the gains you have made throughout a lifetime of physical activity.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475. Readers may also order health newsletters from www.rbmamall.com.

Copy the Story Link