CrossFit demands your all. It asks you to operate in the top 10 percent of exertion, so you probably think of it as being all the rage for buff 20-somethings. Think again.

CrossFit demands your all. It asks you to operate in the top 10 percent of exertion, so you probably think of it as being all the rage for buff 20-somethings. Think again.

Kids love CrossFit, too — and the main reason is that they get to play, says CrossFit Ashland trainer Kymmi Kellens. "It's all about having fun and doing body-weight workouts, not pushing them past the fun point."

The kids, from 5 to 10 years old, climb ropes, play on rings and run about, spiking each other with dodge balls. When hit, instead of being sidelined, they do five burpees and jump back in the game, in keeping with the headlong pace of CrossFit.

CrossFit is an extreme fitness and strength-training routine that pushes you into the top tier of your endurance and strength ability, says owner Emile Garcia, by using a vast range of techniques that are rarely repeated in order — jump rope, gymnastics, rowing, rope climb, pushups, situps, kettlebells, weights — but the kids are introduced to these gradually over the years.

Kids have tons of energy, and CrossFit excels at burning it up, leaving them much more able to sit still and focus on studies in the classroom, says mom Pam Downs, a triathlete.

"It's a great experience for them, a fun outlet," says Downs. "They learn body movement, self-control, agility. They love it. For me, I'm a lot stronger with swimming and biking. It strengthens the core really well."

Going at it with the 20- and 30-somethings (and a sprinkling of over-40s), 70-year-old Ross Pelton, an Ashland fitness and nutrition author, says he quickly realized that CrossFit was great for seniors.

"I could never push myself like this on my own," observes Pelton. "It has changed my life. I'm addicted to it. Although I've been committed to regular exercise all of my adult life, I was very humbled when I began this. It has made me stronger and more aerobically fit than I have been in decades."

Coaches choose weights and intensity levels to fit each athlete — and each athlete's potential for their age, says Pelton, noting a comment from CrossFit founder Greg Glassman: "The needs of an Olympic athlete and our grandparents differ by degree, not kind."

Garcia heartily agrees.

"When Ross started two years ago, he was fit and he biked — but he couldn't jump rope, couldn't run. He has titanium knees, and they told him not to run. Now he does 20-inch box jumps, he runs, does pullups, can squat 160, power-clean 125 and dead-lift 265."

Among the older set, weightlifting is crucial to keep bones and heart strong, says Garcia.

"The gradual loss of muscle mass is one of the key markers of aging," notes Pelton. "Engaging in strenuous exercise such as CrossFit enables me to gain and maintain my muscle mass and strength as I age, rather than gradually losing it like most people do."

Studies of people in their 80s and 90s, especially those by William Evans, show that 12 weeks of high-intensity strength training brings "incredible gains in strength and muscle mass," says Pelton, "if they are willing to work at it."

For Jamie Rosenthal, 34, going daily to CrossFit "is like hitting the reset button, clearing everything out of my mind. My ultimate goal is to keep this extreme fitness as a huge passion all my life, definitely into the older years."

To the powerful beat of hip-hop music, Rosenthal literally drips perspiration. She pauses and pants between sets to gain back some power for the next demanding round.

After her workout, she notes that a family feel tends to develop among CrossFit participants of all ages as they subtly encourage each other to go for the max.

"The suffering is definitely there," says David Jacobson-Fried. "We call it challenge and enjoy it. You don't get it at the Y. Here you have to."

Molly Ochoa, who signed up herself, husband and kids for a lifetime membership, says, "I feel more pushed to my limits here. The result is a sense of overall well-being, with all body systems and organs functioning. The brain functions much better, too, and makes me look at all my choices about eating and living."

What the athletes are doing looks a lot like suffering at the outer limits of endurance, but that's why they come, says Ochoa.

"It's a good way to face difficulties and know we're going to be stronger and be better off. I feel like a warrior, like I'm supposed to be doing this — standing in difficulty with strength."

A motto on the wall sums up the feelings of many CrossFit devotees: "You are the captain of your own ship. Your mind is the wind, and your emotions are the sea. With a strong, focused wind and calm waters, you can accomplish the impossible."

No matter your age.