Volleyball fans worshiped Flo Hyman. A longtime teammate recalled that “People chanted her name … in gyms all over the world,” and other players had to protect her from star-struck supporters who tried to touch her.

Imposingly tall and dauntingly strong, Hyman would have thrived on any team. But her impact on American volleyball made her an icon. Before Hyman came along in 1974, the U.S. women’s team was in tatters. As the LA Times described, the team tanked at the Olympics in 1964 and 1968 and didn’t qualify in 1972. With Hyman’s help the U.S. took fifth place in the 1978 world championships and seemed like shoo-ins for gold in the 1980 Games. America boycotted those Olympics, but Hyman led the women’s team to a silver medal in 1984 despite being the oldest female player present.

In January 1986 Hyman was 31 and still going strong. Per Sports Illustrated, she joined a Japanese team in an elite league and dominated. But during a game in Tokyo she subbed out, sat down, and “slid silently to the floor.” Up to that point she had looked and played well. Not a single doctor had spotted a problem throughout her career. But an autopsy revealed that Hyman had Marfan syndrome, a hard-to-diagnose illness that damages the aorta. Hyman’s heart had a dime-sized defect that caused her aorta to rupture.

Fencing requires a sharp mind. Despite all the simulated stabbing, according to Olympic fencer Sada Jacobson Bâby, the sport is supremely cerebral, primarily relying on strategy and psychology. But even the finest strategic mind couldn’t have anticipated the fate of the great Vladimir Smirnov.

During the early 1980s Smirnov was arguably the best in the world. In 1980 the Soviet fencer earned gold at the Moscow Olympics by breaking a three-way tie in the men’s individual foil. He also earned silver and bronze medals in team competition. The following year Smirnov pulled off an impressive comeback win at the World Fencing Championships after seeing his teammates eliminated in the preliminaries. In 1982 he sought to extend his dominance at the Rome World Championships. Instead, his reign reached a gruesome end.

As Reuters detailed, Smirnov squared off with German Matthias Behr. Both men were juggernauts, regularly described as locomotives in motion. During their fateful match, Behr’s blade broke against Smirnov’s chest. The blade pierced Smirnov’s mask, went into his head, and punctured his brain. Though placed on life support, doctors said he had “no brain reflexes.” Smirnov was 29. The horrifying incident ushered in a new era of safety precautions for fencers.

“It sounded like a baseball bat hitting a ball.” That was how NHL player André Boudrias described moment his teammate Bill Masterton’s head cracked against solid ice. As ABC detailed, it was 1968. Masterton was playing for the Minnesota North Stars. He was also living his dream. As a kid he longed to play hockey on a Canadian team, and when the NHL expanded in the late 1960s, Masterton got his shot.

It seemed like the cherry on an immaculate sundae. Masterton had married his high school sweetheart and adopted two children. He played amateur hockey and joined the U.S. team, and finally he got noticed by the Canadians. He even scored the first goal ever recorded for the North Stars. Masterton took nasty hits and experienced migraines, but he played anyway. Back then a concussion was something that gave you double-vision while you were playing, not a reason to stop playing. In fact, helmets were optional and spurned by most hockey players as a “sign of weakness.”

When Masterton’s skull bounced off the unforgiving ice, it was totally unprotected. An opposing player’s stick had tripped him up, and a second adversary knocked him off his feet. After Masterton landed, his eyes reportedly looked gray. Rapid brain swelling prevented surgery, and nearly 30 hours after his disastrous fall, 29-year-old Masterton was pronounced dead.

A straight-A high school student and star quarterback, 17-year-old Reggie Garrett possessed all the potential in the world. Friend and teammate Bryce Crew said, “He was an all-around great kid. He was perfect.” Unfortunately, Garrett wasn’t physically perfect. A medical examiner revealed that the teen had “an undetectable pediatric heart disease,” telling the Houston Chronicle that “all his organs and muscles were in great shape. It’s just that his heart muscle was not.”

Garrett’s heart gave out during a football game in 2010 while he was trouncing the competition. During the second quarter Garrett threw his second touchdown pass of the night. While celebrating with his team he dropped to the ground. Hundreds of people flocked to the hospital where Garrett was admitted. A hospital spokeswoman told CNN, “It was like the entire football stadium came.”

When hospital visitors heard Garrett passed away, many fell to their knees sobbing. Garrett’s teammate’s still were still playing when received the news. After the game, instead of reveling in a lopsided win, the team came together at the 50-yard line, held each other, and wept.