Nice to see our friends on BBC Radio 4’s Today programme taking an interest in practical fluid dynamics – and perhaps more importantly, stimulating a lively discussion on the subject whilst playing with a bucket of water (yes really – but I wish it had been John Humphrys!) The issue was: how should you hold your fingers to get maximum propulsion when swimming – together or apart, and if so how far? Apparently, this has been the subject of debate in the competitive swimming community for many years, but now research form the Technical University of Eindhoven has provided the answer: there should be about 5-10 degrees between them. Why? It’s down to viscosity: it’s quite hard to squeeze water through the resulting gap, so your hand behaves as if much bigger, or has webs between the fingers. Much more than this and the water can pass through more easily. OK, so add skin friction to form drag. Sounds reasonable.
Just as I thought they had it all sewn up, Duncan Goodhew throws a curve ball by suggesting that the advantage may actually come from relaxing muscles in the wrist, thus conserving energy. Hmm …
Simon Leefe, Technical Director
A clip of the discussion by BBC Radio 4’s Today Programme can be found
