A knee injury while playing football last November sidelined CJ Senter during the playoffs. But rather than sulk on the couch, the 10-year-old from Locust Grove spent his afternoons doing low-impact cardio and stretching. He also stretched his imagination.

Over the next few weeks, CJ’s knee felt better. By then, football was over. But CJ had invented a new way to mix jumps and stay in shape. He also gave his workouts names. Or as he called them, “my signature moves.”

The Fighter (a twist and punch combo). The Shredder (a pushup mixed with a lunge). The Power Jack (a jumping jack followed by a squat).

One night CJ saw some get-fit-quick infomercials on TV. He noticed the fitness gurus were all adults. And then it hit him: “I could do that.”

And he did.

With the support of his parents, Carlos Senter, who owns a barber shop, and his mom, Adrienne Senter, who works for the city of Hapeville, CJ made an exercise video called “Workout Kid.”

Released in May, the DVD has already sold several thousand copies. CJ’s energetic personality — he’s constantly on the move — seems to connect with kids his age and the DVD has helped some lose weight. He’s also led some workouts at school.

In the process, this honor roll student with a bent for science is helping solve the nation’s obesity epidemic. In Georgia, 37 percent of children ages 10 to 17 are overweight or obese, according to the 2007 National Survey of Children’s Health. Nationwide, obesity rates have tripled for children and doubled for adults over the past three decades.

Sedentary lifestyles mixed with easy access to fast food help fuel the epidemic. Kids are spending less time exercising and more time in front of TVs, computers and mobile devices.

“My goal with this is to fight childhood obesity, to get kids on their feet. To get kids into fitness and have fun,” CJ said.

CJ got started on his video with about $25,000 from his family’s savings. The money paid for professionals to film in a local studio and launch a website (www.workoutkid.com).

In many ways, the “Workout Kid” DVD is like other fitness DVDs, featuring two 40-minute workouts, one for beginners and a second, more advanced routine.

The difference is that the upbeat instructor leading a trio of eager students just happens to be a fifth-grade elementary school student who weighs in at 82 pounds.

CJ seems to be quickly growing his fan base. Judi Nicholson of Atlanta bought the DVD for her 9-year-old son, Cameron, in July and already sees changes in her son, who is slightly overweight.

“He’s started to lose weight, but what I also see is he is starting to feel better about himself,” said Nicholson, who learned recently that her son was being picked on at school because of his weight. “He likes the cool moves. There’s been this transformation.”

Nicholson and her son exercise with the DVD together three times a week. (Mom is also losing weight.)

Lean and agile, CJ has always been on the move. At 6 months of age, CJ was able to flip out of his crib. These days, he always seems to be incorporating exercise into his daily routine. Sometimes, he even walks around the living room on his hands.

“After his knee injury, at first, I told him to take it easy, but then he told me, ‘I feel bad when I don’t exercise. I feel good when I exercise,’ ” Carlos Senter said. “That’s when I realized just how important exercise was to him.”

CJ’s physique reflects his dedication. His arms are slim and sculpted. He’s also fast, known on the football field for his speed.

Surprisingly shy, he rarely speaks about his workout video at school, New Hope Elementary.

His school principal, Tim Tilley, said he just recently heard about the DVD.

“He’s kept it very low key,” Tilley said. “We were unaware CJ was becoming the face of fitness. He doesn’t like talking about it, but when he gets in front of a group, he comes out of his shell. I am excited for him. If he can inspire fitness, that is a great thing.”

Tilley said he’s open to the idea of incorporating CJ’s routine into the physical education program but said Henry County would have to sign off on formally using it at school.

On a recent morning in the school gym, CJ stood in front of his classmates and asked if they were up for a game.

“It’s called ‘popcorn,’” he announces. (Popcorn also happens to be a new “signature move,” set to be in the next “Workout Kid” DVD.)

“Every time I say pop, you jump,” CJ said. “Pop. Pop. Pop.”

After jumping, his classmates smiled and cheered.

Back in Locust Grove, CJ, who has a younger sister and an older brother, enjoys getting his whole family moving. They play a touch football game with their own workout rules. Anyone who drops the football has to do 20 pushups.

CJ doesn’t like dropping the ball; but he really doesn’t mind doing the pushups.

“I want to stay fit and live a long, happy life,” he said.

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‘Workout Kid’

DVD is $19.99 and can be ordered online via www.workoutkid.com.