There's been a number of players who have died on/just off the pitch, mostly attributed to cardiac arrest. Here in the states, high school/college football players collapse/die on the field (usually practice) more often than you'd think. It's usually determined they had enlarged hearts, unfortunately it's discovered postmortem. The average person doesn't/can't stress themselves physically enough to cause a problem. Elite athletes can. You may very well be right, but I'd lay odds you're not.