[ponygirl]

Thrashing around with arms and legs is usually associated with a head injury.

He was having convulsions, which is absolutely consistent with cardiac arrest. In fact, the player who died in 71 went into convulsions after he hit the turf face down, according to what I’ve read about it.

[dfwgator]

There is a picture of Dick Butkus standing over Chuck Hughes frantically signalling for help.

[zeestephen]

Blood pressure is zero, but people in cardiac arrest thrash around?

Hmmm...

[David Chase]

I’ve seen both…….usually “convulsions” are quick and at the beginning of cardiac arrest and don’t last long, perhaps just seconds.
Sometimes, there are none at all.