Here it ishttp://www.outsideonline.com/2010156/age-irrelevant
The idea of using exposure to stress as a way to improve athletic performance—or at least not lose it—also comes up in Gifford’s Spring Chicken when he introduces us to a chemical engineer from California named Todd Becker, aka the “world’s toughest nerd.”
Becker runs a health and fitness blog called Getting Stronger and is an outspoken proponent of “hormesis”—a fancy term of Greek origin describing the stress-adaptation process. Becker is bullish on cold-water plunges, fasted workouts, weightlifting, sprinting, and other ways to nudge the body further to prompt positive adaptations. As Gifford points out, this is similar to the way vaccines work: Inject small doses of a virus into a host, which in turn generates the antibodies to protect you from the virus.