In the scientific quest to maximize athletic performance, as teams scrape for every win, Boston Red Sox first baseman Mike Napoli is on the frontier of a burgeoning area of study: sleep.

A number of major league teams, including the Giants, Rays, Rockies, Pirates and Indians, have consulted sleep experts in an attempt to fight fatigue and to exploit the so-called “circadian advantage.”

The man who coined that term, Dr. Christopher Winter, Medical Director of Charlottesville Neurology and Sleep Medicine in Virginia, was the lead author of a large 2009 study that examined how time-zone changes affect outcomes in major league baseball. His group recorded how frequently each team crossed a time zone over 10 seasons and discovered that if a team has to cross a time zone to play a game, it is at a slight disadvantage over and above a visiting team that does not deal with a time change; a team that crosses three time zones has just a 40% chance of victory.

Winter, who is board certified in both neurology and sleep medicine, attributes this to a disruption in circadian rhythms—the body’s sleep/wake cycle, which is synchronized to cues in the environment like light and temperature as well as the hormone melatonin.