From beloved performance expert and bestselling author of Peak Performance comes a revolutionary science-based new definition of toughness - one that focuses on assessing a challenge on a physiological and psychological level. "Steve Magness is one of the giants of modern thinking about high performance across domains. . . . Real Toughness is a crucial read for anyone who cares about delivering their best when the stakes are highest." - Alex Hutchinson, New York Times bestselling author of Endure