When I was in the national guard we trained in the Yakima dessert and one of my fellow soldiers in his 20s and Latino (not sure if he was Mexican) got a bad case of heatstroke or heat exhaustion. Guy was in excellent physical condition as a feather weight boxer. He recovered but he was on his back and not doing well at all for a while. Remember seeing his abdominal area quivering in a weird way and he was pretty out of it. Wasn’t sure what was wrong with him until a medic got there.