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How America's love of watching sports created superhuman athletes

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Athletes' bodies are changing— they're faster, stronger, more efficient and are shattering records from decades ago, and it's all thanks to you. As sports became a spectator event in the 20th century, athletics veered away from a leisure activity for the few, to a multi-billion-dollar industry that attracts the best of the best and encourages them to push to the ever higher plateau of physical feats.