Does swimming after lunch really cause cramp?

This week we're exploring why swimming on a full stomach might cause a cramp, whether it's really true that joints ache more when the weather's cold, and why does tapping the top of a beer bottle make the drink explode? Plus, why do aeroplanes fly high if there's less oxygen for the engines and less air for lift? And why does a child's hair often darken as they age? Join Dr Chris and Kieno Kammies for this week's Ask the Naked Scientist, to find out!