Exercise is our modern obsession, and we have the ubiquitous gyms, fancy workout gear, and fads from Zumba to TRX to CrossFit to prove it. Exercise-a form of physical activity distinct from sports, play, or athletics-was an ancient obsession, too, but it's a largely overlooked chapter in human history. In Sweat, Bill Hayes runs, jogs, swims, spins, walks, bikes, boxes, lifts, sweats, and downward-dogs his way through the origins of different forms of exercise, chronicling how they have evolved over time, dissecting the dynamics of human movement. Hippocrates, Plato, Galen, Susan B. Anthony, Jack LaLanne, and Jane Fonda, among many others, make appearances in Sweat, but chief among the historical figures is Girolamo Mercuriale, a Renaissance-era Italian physician who aimed to singlehandedly revive the ancient Greek art of exercising through his 1569 book De arte gymnastica. Though largely forgotten over the past five centuries, Mercuriale and his illustrated treatise were pioneering, and are brought back to life in the pages of Sweat. While modern society doesn't exercise in quite the same way people of the 16th century, or the Ancient Greeks, Hayes ties his own personal experience-and ours-to its cultural and scientific history, giving us a new way to understand the role of exercise in the 21st century.