Standing still in a packed crowd is harder on the body than walking

Spectators who faint in a crowd usually do so while motionless, and the mechanism is circulation rather than heat alone.

The person who goes down in a full standing section is almost never the one who has been jumping around. It is the one who has been still.

Blood returns to the heart from the legs largely because the calf muscles squeeze the deep veins every time you take a step. Stop stepping, stand upright and locked, hold that for forty minutes in a crush where you cannot shift your weight, and that pump goes quiet. Fluid pools below the knees. Return falls, output falls, the body compensates by tightening vessels and lifting heart rate, and eventually the compensation runs out. The vision narrows, the ears ring, and the person drops. Lying flat fixes it in seconds, which is the clue that it was a plumbing problem and not a heart problem.

Now add the things a stadium contributes. Radiant heat off concrete. Bodies packed close enough that skin cannot dump heat to moving air. An hour in a security queue before entry, sun on the back of the neck, and a hydration plan that consists of one warm drink bought before kickoff. Add alcohol, which pushes fluid out through the kidneys and widens skin vessels. None of these alone puts anyone on the floor. Stacked, at minute seventy of a hot afternoon, they reliably do.

This is why crowd movement design is a medical question and not only a queueing question. A section where people can shift, step out, reach a concourse and come back is a section where the calf pump keeps working. A section where a full row cannot move until the whistle is a section that has effectively immobilised several hundred standing adults. The tight aisle is not just uncomfortable. It is the mechanism.

I would go further and say the current fashion for measuring crowd flow purely in exit-time terms misses the part that actually generates casualty reports. Nobody collapses because evacuation would take eight minutes rather than six. They collapse because they stood without moving in warm still air for an hour with an empty stomach and a beer.

Fix the small things and the fainting curve bends. Shade over queues. Water points that do not require missing twenty minutes of play. Space to move a foot. It is not glamorous engineering, but it treats the crowd as a set of circulatory systems rather than a number to be moved through a gate.