EDEN PRAIRIE -- Minnesota Vikings wide receiver Percy Harvin was taken to a hospital by ambulance after collapsing at Thursday's practice, and coach Brad Childress said Harvin suffered another migraine headache attack.
Harvin, who has dealt with migraines most of his life, has been unable to practice for most of training camp because of the headaches and their symptoms.
Harvin returned to the field on Monday after missing more than two weeks, but at the beginning of Thursday's workout he experienced another episode that was scary enough for the Vikings to halt practice while their teammate received medical attention.
"To see a guy go down, it's never a good thing," defensive end Ray Edwards said. "Just pray that the Lord is with him and he gets back to us safely, and to his family most importantly."
Childress said that Harvin's episode was triggered when he looked up into a mostly cloudy sky to field a punt during a special teams drill. Harvin went inside to see team physician Dr. Sheldon Burns, then came back out to the field.
Soon after, Harvin was seen doubled over and trembling. Players and coaches stood in front of him for privacy while reporters watched from a distance as Harvin received medical attention.
"I don't know how they classify it," Childress said after practice. "Not really a seizure, but he had some trouble over here. I'd be remiss if I tried to qualify it one way or another. It seemed like he was stable."
Childress added: "I'm putting it in a migraine category, just because of what preceded that, but I certainly don't know what put him down on the ground over there, if it was some kind of reaction or what."
The Vikings continued with practice for about five minutes while Harvin was being worked on, then drills were stopped. After Harvin was loaded into back of the ambulance, the team gathered on the field and took a knee in prayer. Players resumed their work for a few more minutes before calling practice over at least an hour early.
"It was an eye-opener," running back Adrian Peterson said. "It's been tough for him. I just encourage him the best way I can."
The ambulance did not leave immediately after Harvin was loaded, and it left without sirens sounding or lights flashing. Though the situation didn't appear grave, the mood was somber.
"Obviously that one hit, and it hit hard," Childress said. "It's always scary for all of our guys when you see a teammate struggling with whatever."
Childress said that Harvin has had to go to the hospital for a migraine before, as a college star at the University of Florida.
"I've seen him with one before. I've gotten him off the field with one before. I've seen the start of one coming on before, but certainly nothing to that magnitude," Childress said.
Migraine triggers vary from person to person, but rising humidity and changes in barometric pressure can cause them, as can the glare of the sun.
Since Harvin started missing practice as a rookie last year, the Vikings have received all kinds of suggestions to treat the migraines. Harvin has sought treatment from expert after expert, but Thursday's episode was the latest example of how hard of a problem it is to solve.
"I think by this happening it kind of lets the team know exactly how hard it is," left tackle Bryant McKinnie said. "A lot of times it doesn't take place in front of us. So now by people actually seeing it, they see it's really not a joke.
"Some of us knew for real that he was really suffering from it," McKinnie said. "Maybe some other people in some of their minds they weren't sure, but I think they are aware now."