When you picture fitness instructors, hard-bodied folks—enthusiastically urging sweaty exercisers to work harder, go faster—probably come to mind.

You may be surprised to learn that an increasing number of personal trainers are closer in age to your parents than your kids. And believe it or not, working out with a trainer who's pushing 70 (or beyond) may be just the ticket to helping an aging population achieve—and maintain—a level of physical fitness that will keep them as healthy as possible into old age.

Why are there more older exercise professionals today than in the past? The answer is simple—there are more of them. The baby boomers have taken over the workout world. "The changing demographics are fueling this trend," says Cedric Bryant, PhD, FACSM, chief science officer for American Council on Exercise (ACE). "Fitness participants are also maturing." The average age of an ACE-certified professional is 42, according to Bryant, a number that encompasses a multitude of people in their 60s and 70s as well as in their 20s.

Many fitness professionals enter the field when they're young and stay in it for decades, Bryant explains adding that there's also a substantial population of career changers—those who spent years working in other fields and became certified fitness instructors in middle age or later.

Why Older May Be Better

Older fitness instructors are invaluable when it comes to motivating other seniors to work out. "The older trainer has an easier time understanding and relating to the unique needs of his older clients," says Bryant. Older pros often communicate better with their peers and are better able to modify exercises for conditions such as arthritis, high blood pressure, and diabetes. Don't expect them to have perfect "gym bodies." Many people find older trainers less intimidating than flawlessly sculpted 20-somethings who may not suffer from aches and pains after a tough workout. They can, however, be a very inspiring example of health and fitness in midlife and beyond. "Fit folks in their 70s and 80s really help to dispel the notion that age dictates what you can do at the gym," Bryant believes.

But regardless of the age of your fitness instructor, it's crucial that he or she is properly certified from an accredited fitness organization in order to have the knowledge to help clients reach their physical goals and avoid injury. ACE or IDEA Health & Fitness Association are two good organizations that offer certification courses and continuing education.

Ben Greenfield reviewed this article.