I’M puzzled by the crash helmets worn by those riding push bikes.

These crash helmets are normally lined inside with a relatively hard plastic foam. That renders those crash helmets useless in one respect.

Clearly those crash helmets offer protection against head injury caused by falling against a sharp object, like the sharp edge of a kerb stone. However, they offer next to no protection against an equally likely injury, namely rapid deceleration of someone’s skull which is too much for the brain (which is a very flexible organ) to withstand.

In fact as far as the latter type of injury is concerned, those helmets might just as well be lined with concrete. In contrast to polystyrene, there are plastic foams with plenty of give in them, which would reduce deceleration, it seems to me. Has anyone got an answer to this?

Ralph Musgrave, Durham