Making and taking a hit chest to chest, instead of skull to skull, is easier to remember if you're not wearing a helmet, say University of New Hampshire Wildcat football players. Jack Rodolico/New Hampshire Public Radio hide caption

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Members of the St. Louis Rams raise their arms to protest the grand jury decision in Ferguson, Mo., before a game last month. The players faced a backlash from St. Louis police and have been asked to apologize. L.G. Patterson/AP hide caption

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Portugal's Cristiano Ronaldo takes a water break during the 2014 World Cup soccer match between Portugal and the U.S. in Manaus, Brazil, on June 22. Siphiwe Sibeko/Reuters/Landov hide caption

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Ray Copeland, a football coach at Bishop McGuinness High School, puts his players through a workout in Oklahoma City in 2007. As is often the case in much of the U.S., the first day of high school football practice that year began in a heat wave. AP hide caption

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Sarah Piampiano holds two energy gels, one with caffeine and one without, as she runs in this year's Ironman World Championship. Murray Carpenter for NPR hide caption

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Lance Armstrong competes in the Ironman Panama 70.3. triathlon in Panama City, Panama. Arnulfo Franco/AP hide caption

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Triathletes begin the 1,500-meter swim (just under 1 mile) in the Hudson River as part of last year's New York City Triathlon. Two race participants died during this year's swim portion. Dario Cantatore/Getty Images hide caption

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