(NBC)- Many professional athletes have turned to "cryotherapy" for rehab.
Users enter a chamber that pumps in liquid nitrogen, dropping the temperature inside to 300 degrees below zero.
They stay in for two to three minutes, and because it is not a "wet cold" like an ice bath, they say the cold is bearable.
"It really helps with deep tissue relaxation, muscle relaxation, it's has been helpful with muscle spasms and it speeds up the healing process of injuries as well," said Dr. Jonas Kuehne, who runs a cryotherapy clinic in Los Angeles.
He says the extreme cold releases endorphins, natural pain relievers in the body, and reduces inflammation after intense workouts.
Athletes say cryotherapy gives them an edge by letting them skip the recovery time needed after hard training.
"I trained probably for a few hours right before I came here, and right now I feel like I can go again," said Jason Deutchman, basketball player. "That's not a usual thing for me."
Some sports medicine doctors say the cryotherapy claims aren't crystal clear.
"There's no doubt that ice therapy, cryotherapy, works for reducing inflammation. The question is can you do it quicker in one of these chambers, and again, the evidence is not there to support it," said Dr. Andrew Gregory, Vanderbilt University Sports Medicine Physician.
The treatment is not regulated by the food and drug administration.
Dr. Kuehne says cryotherapy can also be used for cosmetic purposes. He says patients' skin appearance has improved after a few sessions.
It costs $70 per session and is only available in a few cities right now.
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