You know what is supposed to happen when you grow old. You will slow down, you will grow weak, your steps will become short and mincing, and you will lose your sense of balance. That’s what aging researchers consistently find, and it’s no surprise to most of us. However, if you stay physically active your entire life, slow and weak are adjectives you will never use as you age gracefully.

It is worth remembering that the people in those studies were sedentary, said Dr. Vonda Wright, a professor of orthopedics at the University of Pittsburgh.

Dr. Wright, a 40-year-old runner, decided to study people who kept training as they got older or began competing in middle age. She wanted to know what happens to them and at what age does performance start to decline.

Their results are surprising, even to many of the researchers themselves. The investigators find that while you will slow down as you age, you may be able to stave off more of the deterioration than you thought. Researchers also report that people can start later in life — one man took up running at 62 and ran his first marathon, a year later, in 3 hours 25 minutes.

It’s a testament to how adaptable the human body is, researchers said, that people can start serious training at an older age and become highly competitive. It also is testament to their findings that some physiological factors needed for a good performance are not much affected by age.

Researchers say that you should be able to maintain your muscles as you age, including the muscle enzymes needed for good athletic performance, and you should be able to maintain your ability to exercise for long periods near your so-called lactic threshold, meaning you are near maximum effort.

But you have to know how to train, doing the right sort of exercise, and you must keep it up.

“Train hard and train often,” said Hirofumi Tanaka, a 41-year-old soccer player and exercise physiologist at the University of Texas.

Dr. Tanaka said he means doing things like regular interval training, repeatedly going all out, easing up, then going all out again. These workouts train your body to increase its oxygen consumption by allowing you to maintain an intense effort.

“One of the major determinants of endurance performance is oxygen consumption,” Dr. Tanaka said. “You have to make training as intense as you can.”

When you have to choose between hard and often, choose hard, said Steven Hawkins, an exercise physiologist at the University of Southern California.

“High performance is really determined more by intensity than volume,” he added. “Sometimes, when you’re older, something has to give. You can’t have both so you have to cut back on the volume. You need more rest days.”

Dr. Hawkins, who says he no longer runs competitively, adds that he tries to put his findings into practice. “I run a couple of times a week and I try to make it as fast as I can,” he said. “I’m not plodding along.”

Vigorous exercise is rapidly gaining popularity among the over 40 demographic. Doing bursts of hard exercise not only improves cardiovascular fitness but also the body’s ability to burn fat, even during low- or moderate-intensity workouts.

Dr. Hawkins has also been amazed by some people who seem to defy the rules of aging, people he describes as “those rare birds who get faster.” Some subjects in Dr. Hawkins’s research study, which followed runners for nearly two decades, actually had better times when they were 60 than when they were 50.

“We really don’t know why,” Dr. Hawkins confessed. “Maybe they were training harder.”

Then there are people like the 62-year-old man who suddenly took up running and began running fast marathons. That man’s inspiration to become a runner, said James Hagberg, an exercise physiologist at the University of Maryland, was watching a lakefront marathon in Milwaukee. “He got all fired up,” Dr. Hagberg recalled.

And there are people like Imme Dyson, a 71-year-old runner. She took up running when she was 48 and loved it, she says, from the moment she put on a pair of running shoes. Her daughter, who had been a college triathlete, told her how to train.

“She said, ‘Mom, if your workout didn’t hurt, you didn’t work hard enough,’ ” Ms. Dyson said.

“Working consistently really is the recipe,” she said. And it has made a difference for her, allowing her to run races, from 5K to marathons, so fast that she is consistently among the best in the nation in her age group. She has run a 15K cross-country race in 1:19:08, a pace of 8:29 a mile. And she ran a 10K race in 51 minutes 50 seconds, a pace of 8:20 a mile.

Not every aging athlete does so well. But Dr. Hagberg found that studies of aging athletes sometimes were distorted because they included people who had cut back on or stopped training. That’s understandable; there is no reason, researchers say, to exhort everyone to maintain an intense effort decade after decade.

You don't have to be an athlete to age gracefully. Even non-athletes and people who maintain a vigorously active lifestyle as they age, are stronger, less prone to disease and gain less weight than people who exercise at more moderate levels. The time to think about exercise is before you think you need it.

• Why Is Vigorous Exercise Gaining More Recognition?
  
• Vigorous Exercise May Slow Women's Bone Loss
• Vigorous Exercise Keeps People Thin with Age
• Vigorous Exercise May Prevent Pain
• Vigorous Exercise Keeps Knee Cartilage Healthy
  

Reference Sources 98, 133

...............................................................................................................