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As long as the football player or runner is doing 30mph+ in the sprint and starts off with their CG elevated a foot above the normal standing position, then yes, they're exactly the same.

Yes they may be slower but they are more likely to actually fall (or be tripped) Combined with the number of footballers against number of grass track cyclists and potential number of head injuries etc, etc,.

I reckon you would be hard pushed to find any discussion on helmets in any football forums...