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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Maria Sharapova returns the ball during the semifinals of the French Open on June 5. She used platelet-rich plasma to treat a shoulder injury. Miguel Medina/AFP/Getty Images 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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University of Louisville cheerleaders hurled into the air during the first half of the NCAA Final Four tournament college basketball semifinal game against Wichita State in April. Charlie Neibergall/AP hide caption

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Germany's Laura Ludwing wears Kinesio tape during a women's beach volleyball match on July 31, 2012, during the London 2012 Olympic Games. Daniel Garcia/AFP/Getty Images hide caption

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