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Turning back the clock

<em>A new book, "Younger Next Year: A Guide to Living Like 50 Until You're 80 and Beyond," by authors Chris Crowly and Henry Lodge, says it's possible to turn back the clock if you're willing to try seven simple steps. Read an excerpt of their book.</em></p>

A new book, "Younger Next Year: A Guide to Living Like 50 Until You're 80 and Beyond," by authors Chris Crowly and Henry Lodge, says it's possible to turn back the clock if you're willing to try seven simple steps. Read an excerpt of their book below:

Chapter Five: The Biology of Growth and Decay: Things That Go Bump in the Night
Biologically, there is no such thing as retirement, or even aging. There is only growth or decay, and your body looks to you to choose between them. So, this is the place where we take you backstage to look at that process—at the actual mechanisms of the new biology that has forever changed our thinking about aging. If things get mildly complicated, just remember that we are always talking about growth and decay. Come back to that simple point, and the details will fall into place.

First off, you may think your body is a “thing,” like the Empire State Building or a car, but it’s not. It’s made of meat, sinew and fat and many other parts that break down over time and have to be constantly renewed. The muscle cells in your thigh are completely replaced, one at a time, day and night, about every four months. Brand-new muscles, three times a year. The solid leg you’ve stood on so securely since childhood is mostly new since last summer. Your blood cells are replaced every three months, your platelets every ten days, your bones every couple of years. Your taste buds are replaced every day.

This is not a passive process. You don’t wait for a part to wear out or break. You destroy it at the end of its planned life span and replace it with a new one.

Stop for a moment, because that’s a whole new concept. Biologists now believe that most cells in your body are designed to fall apart after relatively short life spans, partly to let you adapt to new circumstances and partly because older cells tend to get cancer, making immortal cells not such a great idea. The net result is that you are actively destroying large parts of your body all the time. On purpose! Throwing out truckloads of perfectly good body to make room for  new growth. Your spleen’s major job is to destroy your  blood cells. You have armies of special cells whose only job is to dissolve your bones so other cells can build them up again, like pruning in autumn to make room for growth in the spring.

The trick, of course, is to grow more than you throw out, and this is where exercise comes in. It turns out that your muscles control the chemistry of growth throughout your whole body. The nerve impulse to contract a muscle also sends a tiny signal to build it up, creating a moment-to-moment chemical balance between growth and decay within the muscle. Those two same signals are then sent to the rest of your body. If enough of the growth signals are sent at once, they overwhelm the signals to atrophy, and your body turns on the machinery to build up the muscles, heart, capillaries, tendons, bones, joints, coordination, and so on.So exercise is the master signaler, the agent that sets hundreds of chemical cascades in motion each time you get on that treadmill and start to sweat. It’s what sets off the cycles of strengthening and repair within the muscles and joints. It’s the foundation of positive brain chemistry. And it leads directly to the younger life we are promising, with its heightened immune system; its better sleep; its weight loss, insulin regulation and fat burning; its improved sexuality; its dramatic resistance to heart attack, stroke, hypertension, Alzheimer’s disease, arthritis, diabetes, high cholesterol and depression. All that comes from exercise. But let your muscles sit idle and decay takes over again.

Exercise Is Healthy Stress
When you exercise fairly hard, you stress your muscles. You drain them of energy stores, and you actually injure them slightly. The stress of exercise is good, because it tears you down to build you back up a little stronger. You wear out little bits that need to be replaced after each use, requiring lots of fine tuning and minor repairs. This type of injury is called adaptive micro-trauma, and it’s critical to your growth and health. It’s the signal to your body that it needs to repair the damage—and then some. It needs to make the muscle just a little stronger. To store just a little more energy for tomorrow. To build a few more tiny blood vessels inside the muscle. To get a little younger.

Excerpted from "Younger Next Year: A Guide to Living Like 50 Until You're 80 and Beyond," by Chris Crowley and Henry S. Lodge. Copyright © 2004. Excerpted by permission of Workman Publishing Company. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.