Use it or lose it

DEAR DR. DONOHUE: How much time can I take off from exercising without losing everything? I'm getting stale, and I think a break would do me some good. I have been exercising every day for years. I wouldn't mind becoming a couch potato for a few months. -- B.P.

ANSWER: When professional athletes, like tennis players, feel they're becoming stale, they do take time off. They don't, however, become couch potatoes. You can reduce the amount of time you spend exercising or you can reduce the intensity of your exercises, but you shouldn't abandon them altogether.

In just two weeks of not exercising, muscles begin to shrink. You might not see the change, but you can detect it by noticing you have to tighten the wristband on your watch.

In three months of no exercise, conditioning has declined to near pre-exercise levels. Muscle enzyme activity is only half what it used to be. Muscle enzymes convert body fuels into energy. The heart begins to beat faster. That indicates that it can't pump as much blood as it did with each beat. Body fat increases. A person's aerobic capacity -- the ability to support sustained exercise like distance running -- greatly diminishes.

If you want to take time off, that's OK, but do something. Exercising once or twice a week prevents the precipitous decline that comes with stopping all exercise.

If you feel stale, how about adopting a different program, doing things you haven't tried? Biking, swimming wall climbing, whatever, just do something.

DEAR DR. DONOHUE: I have heard that jumping rope is the best exercise anyone can do. I don't like to jog, so I thought I would take it up. I also heard that 10 minutes of rope-jumping equals 30 minutes of running. If that is true, then it appeals to me even more.

Will you provide some information on jumping rope? Is it hard on the knees? -- C.W.

ANSWER: Jumping rope is extremely vigorous exercise, so be forewarned. Ten minutes of ropejumping doesn't equal 30 minutes of running. I'm not sure where that got started, but it isn't true.

Start a rope-jumping program modestly. Begin with 80 turns of the rope a minute. If you can jump for two minutes, that's good. At this rate, you burn 10 calories a minute. Rest after two minutes, and then do another two. Work your way to the point where you're turning the rope 120 times a minute and doing 10 to 15 straight minutes of jumping without a break. It will take you months and months to reach that level.

To find the correct rope length for you, stand on the center of the rope and draw the ends up. When they are at armpit height, that is the length you want.

Jump about 1 inch off the ground. Higher jumps are taxing on the legs.

Land on the balls of the feet and then lower your heels to the ground, so they absorb some of the landing shock.

Turn the rope with the wrists, not with the arms and elbows.

Jumping isn't hard on the knees. You can protect them by keeping them slightly bent when you land.

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. 2006 North America Syndicate Inc. All Rights Reserved