Swimming star Alexander Dale Oen, one of Norway's top gold medal hopes in the upcoming Summer Olympic Games in London, died Monday at his hotel near a training facility in Flagstaff, Ariz.

The 26-year-old world champion in the 100-meter breaststroke suffered an apparent heart attack, according to Norway's Olympic Committee.

According to The Associated Press, Norway's Swimming Federation "said Dale Oen had only a light training session on Monday and played golf that day. But teammates became worried when the swimmer spent an unusually long time in the shower and entered his bathroom when he failed to respond to their knocks on the door. The federation said 'they found Dale Oen laying partly on the floor, partly on the edge of his bathtub.' "

Reuters adds that "Dale Oen won his world title last year in the immediate aftermath of the massacre of 77 people by far right fanatic Anders Behring Breivik in central Oslo and on the island of Utoeya. He had struggled with his emotions after attacks that sent Norway into national mourning, touching the Norwegian flag on his swimming cap every time he entered the pool deck."

Following that victory at the world championship in Shanghai last July, Dale Oen said "we need to stay united. ... Everyone back home now is of course paralyzed with what happened but it was important for me to symbolize that even though I'm here in China, I'm able to feel the same emotions."

The Wall Aquatic Center at Northern Arizona University is a popular training facility for elite swimmers because of the area's high altitude (about 7,000 feet above sea level). As All Things Considered has previously reported, high altitude training is said to "stimulate red blood cell production, which improves muscle endurance."

Dale Oen was among swimmers from eight nations who trained at the facility before the 2008 Olympics in Beijing. He won the silver medal in the 100-meter breaststroke at those Games.

According to The Norway Post, Dale Oen has recently been dealing with "an infection in a shoulder."

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