Staying active in retirement doesn't have to mean just getting out of the house and seeing friends and family once in a while. For many older people, retirement affords the time to exercise regularly and, for some, get into even better shape than when they were young.

Just because you’re gray or graying doesn't mean you can't achieve a high degree of fitness and wellness.

In a recent article on Fitbie, Mary Squillace profiled several senior athletes who could give even twentysomethings and thirtysomethings a run for their money in a strength competition. Here are some of their fit-spiring stories.

Baywatch: The Golden Years

Ed Peters has been a lifeguard in New York for over 50 years—he started in 1960, earning $6 a day. In his time, he's encountered quite a few people who need to be rescued. He's also come across some who don't.

"I went out for this one guy who was about 250 pounds," Peters related in this video interview,"and before I get to him, he grabs my arm and then he climbs up me and grabs me around the neck and says, 'Please don't let me die!' And I go, 'Stand up, you're on a sandbar!"

For Peters, the beach isn't just a place to visit or work— it's a lifetime.  "You worked six days a week and you sat on the sand for eight hours a day, without a break. I met my wife down there, raised my children down there. I don't know what else you need, you know?"

Now 70 years old, Peters is still lifeguarding. To keep his certification, he must pass a rehire test every year. To train for it, he exercises daily— biking, lifting weights and swimming.

"You have to run a quarter mile under a certain time and you have to swim a hundred yards," he explained. "That was, like, nothing years ago. Unfortunately, it gets harder and harder."

But Peters keeps doing it, because lifeguarding is his passion. And every year, he keeps passing the physical requirement exam.

"How many of you are going to say that, that when you leave this earth that you were doing something you loved?," he wondered. "To be a champion is to be comfortable with what you've accomplished, to know that you've done the best that you can do, and to continue to do it as long as possible."

Life isn't a race. It's a marathon.

Just ask Gladys Burrill, of Oregon. Known as "the Gladyator," Burrill didn't start running marathons until she was 86 years old. By the time she was 92, in 2011, the nonagenarian had completed the grueling Honolulu Marathon five times and had become the oldest woman ever known to have completed a marathon— a fact documented in the Guinness Book of World Records.

How does she do it? Positivity.

"I'm fortunate to be in good health, but age is only a number. People can be old at 40," Burrill told The Oregonian." It's important to think positive and to dream."

Burrill adheres to a mostly-vegetarian diet (occasionally indulging in a bit of fish or poultry). She power-walks 30 to 50 miles weekly and runs on her own all-weather track at home. In order to prepare for the Hawaii climate, which is humid, she runs early in the morning, when fog is dense and low to the ground.

Now widowed, she is grandmother to 18 and great-grandmother to 26. When she's not running, she's gardening. And she has a lifetime of achievements to think over as she does.

Strength and grace.

Ernestine Shepherd is 77 years old. She's also the world's oldest competitive female bodybuilder. Having taught fitness classes for years at her church, she took up bodybuilding at the age of 71, even though most competitive bodybuilders bow out in their 30s. What's truly astounding, though, is that Shepherd didn't start working out— even on a casual basis— until she was 56!

It was in that year that Shepherd, while trying on swimsuits, wasn't satisfied with the way her body looked. She and her sister, Mildred, made a pact to become the world's oldest female bodybuilders. Although Mildred passed away, Shepherd carried on with their dream and achieved remarkable success.

Every day, before dawn, she runs 10 miles in the park. She then works out in the gym, works as a personal trainer and teaches two fitness classes geared toward helping other seniors achieve healthier, more active lifestyles.

In an interview with Time, Shepherd acknowledged a surprising source for her inspiration.

"You will laugh when I tell you. I just love some Sylvester Stallone," she said. "I was inspired by the Rocky Balboa character and I found it was not about how hard you can get hit, but how you keep moving forward. That is how winning is done. The Rocky movies make me ready to take on the world."

Senior living doesn't have to be sedentary.

And getting old doesn't have to mean getting weak. Talk to your primary care doctor or geriatrician about developing an exercise program that is tailored to your unique physical needs, but that is also designed to help you improve your strength, mobility and agility over time.

You might also consult a senior nutrition expert, to develop the right diet and menu plan to support your fitness goals and achieve better wellness overall.

The seniors profiled above are living fulfilling, healthy and strong lives. It may take a lot of dedication, and a lot of perspiration, but you too could be a source of inspiration. Take the first steps to get out and get moving today.