Cross Fit is an extreme workout, designed originally for elite athletes. It's a military-style exercise class that pushes bodies to the brink. But some trainers worry that Cross Fit can cross the line when it comes to your health.
"When you're younger, you can take more abuse and get away with it. but as you get older with wear and tear, you are increasing your risk of injury," said Steve Nudelberg, a marketing consultant who knows that first hand.
He's competitive in business and in the gym.
"Part of being good mentally is being good physically, so I work out every day at 5:00 a.m.," he said.
But Nudelberg was sidelined recently when he pushed himself a little too hard during Cross Fit.
Critics warn that safe technique can be sacrificed for speed and volume.
"Whatever weakness I had in my shoulder just gave out," Nudelberg said. "I had severe pain in the neck and shoulder.".
Personal trainer Doug Jackson says shoulder injuries are common with Cross Fit, especially with the over 40 crowd.
Many trainers emphasize the importance of slow, controlled and steady workouts that are high in repetitions.
Jackson says it's important to strengthen your core muscles safely to avoid the number one exercise injury to the lower back. His advice to get you lean and mean?
"A total body strength training program, 8 to12 exercises, 2 to 3 sets of each, 8 to 12 repetitions per set," Jackson said.
In addition to injuries to shoulders and back, there have been some studies out recently, saying that Cross Fit, because it is so intense, can cause a dangerous release of proteins that can damage your kidneys and cause painful swelling.
The best advice: moderation, push yourself but remember, you're not 21 anymore.