It's common for older adults to start to slow down as they age. 

Maintaining bone and muscle strength, balance and cardiorespiratory health can become more of a challenge. As a result, some seniors have a hard time staying as physically fit as they once were.

This can lead to a difficult cycle, however, as the less activity you get, the weaker those systems can become, which further limits mobility. The way you stay active as you age may change over time, but that doesn't mean it has to stop entirely. In fact, many inspiring seniors are able to make stunning athletic achievements at every age:

1. Johanna Quaas, 91-year old gymnast
Johanna Quaas wowed the audience at the June 2017 International German Gymnastics Festival with an impressive parallel bar routine that would be inspiring at any age - but at 91-years-old, Johanna's athletic skills are particularly impactful. According to the Washington Post, Johanna currently holds the Guinness World Record for being the oldest gymnast, a title she's held since 2012.

She began the sport in 1934 - when she was just 9 years old. After having her family, she took some time off to focus on coaching, but began competing again for herself when she was 56. 

On top of that? She's also a championship handball player as well!

"I do gymnastics to avoid being susceptible to falls and that is a good preventive tool," she said.

When she was first named the world's oldest gymnast, her goal was to still be participating in the sport when she was 90. That milestone has come and gone, and Johanna has no intention of stopping any time soon. 

2. Ed Whitlock, 85-year-old runner
Ed Whitlock made a name for himself in the world of marathon running with a number of impressive titles and records, including being the first person over the age of 70 to complete a full marathon in less than three hours. The New York Times Reported that his most recent record was set in October 2016 at the the Toronto Waterfront Marathon - Ed became the oldest person to finish a marathon in less than four hours. 

Running a marathon is grueling work - to maintain speed for 26.2 miles takes incredible strength and endurance. It often requires a lot of training and supplemental exercises. Yet Ed didn't need any special guidance or resources for his achievements. He simply ran laps for a few hours every day. When he set his record at the Toronto Waterfront Marathon, he was wearing shoes that were 15 years old. 

"I believe people can do far more than they think they can," Ed told The New York Times. 

Scientists studied Ed's physiology in 2012 and found that his muscles had an incredible capacity for taking in oxygen, which can greatly improve endurance. Many athletes, like runners and swimmers, focus on training that can help them increase their own intakes, known as VO2 max. Ed's consistent running schedule made it easier for his body to process oxygen, which made it easier for him to run, creating a fitness cycle that helped him to excel in his sport. 

Just months after completing the Toronto Waterfront Marathon, Ed passed away from prostate cancer in March 2017. He was an incredible example of what people can achieve at any age so long as they are willing to put the time and energy into it. 

3. Charles Eugster, 97-year-old rower and body builder
During his university years, Charles Eugster was on a competitive rowing team and then joined the Swiss Army. He told The Telegraph that he let his fitness routine start to falter as he began his professional career and started a family in the 1940s and 50s, but decided he wanted to make a change to get back in shape when he was 63 years old. 

Charles picked up his old rowing hobby again and started signing up for competitions. He racked up an astonishing 40 gold medals at World Rowing Masters by the time he was 93 years old.  

Those achievements weren't enough for him, however. Though he was accomplishing great things in rowing, he felt his overall fitness was below where it possibly could be. As a result, he joined a body-building club when he was 87 years old, and eventually moved on to running and swimming as well. He stated that anyone his age could participate in these events if they were willing to train appropriately.

When he passed in April 2017, he held U.K. records in five different athletic events and one world record. 

4. Dick Roche, 77-year-old roller derby skater
At 77-ears old, Dick Roche is the world's oldest known active roller derby skater. At age 70, he became a founding member of the Lane County Concussion roller derby team in Eugene and Springfield, Oregon, where he has skated competitively for several seasons, according to the LLC. 

Roller derby is a fast-paced, full-contact sport that requires a significant amount of training to stay in shape. Players must stay on roller skaters for the duration of each game and often use full-force hits to try and knock opponents down. Despite the intensity of the game, Dick is a central figure in men's competitive roller derby who doesn't let his age keep him on the sidelines. 

"I've got lots of energy, I'm having fun," he told the University of Oregon, adding that he joined the sport because it looked like fun.

His daughter and two grandchildren also play roller derby. 

5. Don Pellman, 101-year-old Olympian
In the 2015 San Diego Senior Olympics, Don Pellman set five new world records - at age 100. The New York Times reported that he was the oldest person competing in the games when he became the first centenarian to complete the 100-meter dash in under 27 seconds, and the first to clear the bar at an official height for the high jump. 

In addition to his achievements as the first centenarian, he also set new records in shot-put, long jump and discus for his age bracket.

As a youth athlete, Don was a gymnast and high jumper. The Times reported that he left his college track career to get a job during the Great Depression. It wasn't until after he retired in 1970 that he, with the urging of his children, decided to once again pick up the sport he still missed. He's completed 127 meets since then. He's now 101 years old. 

Don clearly loves to push himself and aim high - despite his impressive feats, he said he was disappointed he didn't perform even better on the high jump. Nonetheless, he's still tied with Jesse Owens's record for setting the most world records in one day.

Staying in shape as you age
While not everyone needs to be setting records in their chosen sport in their 80s, 90s or 100s, staying in shape is still important for seniors. The Centers for Disease Control and Prevention recommends that adults get at least 150 minutes a week of moderate exercise. In addition, they should do two days a week of strength training. This can be as simple as taking a brisk walk and performing some low-impact body weight exercises at home. Gym memberships, group fitness classes or joining a sports group are good ways to also stay active for those who enjoy such hobbies. 

If you've been inactive for awhile, it's not too late to get into better shape at any age! Talk to your doctor about finding a safe fitness plan that works for you - you can start slowly and gradually increase the intensity and amount of time you put into activities until you reach your personal fitness goals.