HOUSTON -

Walk into any CrossFit gym and you'll notice that it looks nothing like your conventional workout facility. There are no treadmills or weight machines, but instead, you will find kettle balls, pull up bars, climbing ropes and gymnastics rings.

But, don't let its simplicity fool you. CrossFit is intense. Many people say they get results in just a few weeks. But, the intensity or obsession, as some would argue, can have a downside.

"There has been a lot of reports of rhabdo with CrossFit," said Dr. Vijay Jotwani with Houston Methodist Orthopedics & Sports Medicine.

Dr. Jotwani is referring to social media buzz about rhabdomyolysis ,or rhabdo for short. It happens when muscles are damaged from excessive exercise. The muscle breaks down and spills protein into the blood and certain proteins can be toxic to the kidneys.

So how serious is this?

"Rhabdo can be deadly," said Dr. Jotwani. "When you have kidney failure like this and you don't recognize it, you may need dialysis. It can lead to kidney shutdown. It can raise the potassium levels in the blood which can cause heart problems."

Before you cancel your CrossFit membership, Dr. Jotwani says rhabdo isn't just a CrossFit issue. He has seen it with football players and military recruits.

Other doctors we asked say they have diagnosed rhabdo in marathon runners and soccer players.

"I think people need to be aware of it," said Teresa Trojanowski, co-owner of CrossFit Central Houston in the Meyerland area. "At the same time, don't be afraid to try CrossFit or any sport."

At CrossFit Central Houston, they preach technique, consistency, followed by intensity. Trojanowski said she has never seen rhabdo at her gym.

"We are here to keep you safe, we're here to get you healthy," said Trojanowski. "We're here to make you better for life and that includes preventing injuries."

Dr. Jotwani says the key to avoiding rhabdo is to mix up your workout. Do not focus exclusively on one muscle group and build up your reps slowly.

"You want people to work out," said Jotwani. "But it's when you don't listen to your body, and you pass the point of that good intense workout to one that's dangerous, that's when you run into trouble."

And, know the symptoms. They include weakened and swollen muscles, and changes in urine.

Click here to learn more about CrossFit Central Houston.