With almost a third of children in the U.S. classified as overweight or obese, anything that inspires the younger generation to lead a healthier lifestyle should be a good thing.
But some medical experts have expressed concern about the influence of CJ Senter, ten, from Locust Grove, Georgia, who is soaring to fame under his alias Workout Kid.
The pint-sized fitness guru, who boasts an impressive 'eight-pack' of muscles on his stomach, has sold and donated nearly 4,500 workout DVDs.
And while his peers are responding positively to his advice - the reaction to his appearances is not unlike the reception a pop star might receive - there are concerns that CJ is inspiring premature body image-related issues.
Last night's edition of Nightline saw children as young as nine displaying a desire for the same kind of overdeveloped muscles.
And an 11-year-old admitted to having lost 10lb in three weeks by following the Workout Kit routine daily.
It is clear that weight-loss is the goal of CJ's fitness plan. He tells the show: 'You can go outside and have fun, but some kids, they'll just go outside for like 10 minutes and come back in.
But if you just do a workout, your body will sweat more.
'Sweating, it lets, you know, you're losing weight. You're really working.'
But it seems this is part of a bigger trend.
Doctors are reporting rising numbers of children with stress-related injuries, which they attribute to excessive workout regimes.
Dr Robert Gotlin, director of the Orthopedic and Sports Program at New York's Beth Israel Medical Center told the show that children are now doing too much exercise.
'What we have nowadays is children playing multiple sports or doing multiple activities,' he said, explaining that just an hour a day was adequate.
'CJ, running track, playing football and working out... that's overuse set-up, because he's doing three different things at one time.'
He added that he had seen incidences of tendonitis, bone and ligament injuries soar.
'In my practice now, I've seen doubling of injuries to young kids, age 10 or 9 or 8, with overuse injuries because they're doing more now,' he said.
'The problem with ligament injuries in children is the fact that ligaments in kids are very, very strong. So what happens is they don't tear but they pull the bone. And the ligament can actually pull the bone off the bone.'
CJ's parents insist that their son's unlikely career is not forced, and that there is no financial motive to the Workout Kid project.
His mother, Adrienne Senter, explained: 'It wasn't anything he set out to do on purpose. Just with exercising and really just normal play for a child, he developed a physiq
