PEORIA, Ariz. — James Shields was hurting.
The symptoms were more widespread fatigue than acute pain. It was the summer of 2013, and the then-Kansas City pitcher’s legs were dead. His right shoulder was dragging. The setting did not help; the Royals were on the road in Arlington, Texas, where thermometers registered north of 100 degrees.
So one sweltering morning, Shields stepped into a futuristic chamber on the recommendation of a friend. Soon, the chamber, which resembled an upright MRI machine, filled with nitrogen vapor. The temperature inside plummeted to below minus-100 degrees … as in Celsius.