A question I get asked a lot relating to swim technique is whether to swim with thumbs in or out when pulling. I looked into this area of the stroke a few years ago. In particular finger spacing and how finally the sports scientists had caught up and told us that an ideal spacing between the fingers was 3mm. Most elite swimmers have this gap as it improves the size of the usable surface area of the hand and provides a larger, firmer anchor to launch you forwards.
I shifted to this hand shape a few years ago and took 1 stroke off my 25m stroke count feeling less slipping, a firmer hold and a bigger paddle to pull myself forwards with. It was significant. During lectures about the Thumb position when asked due to the lack of research and how so many Elite swimmers have done well with either the thumb in or out I glossed over it and offered that both were ok. I was not going to unteach one over the other or introduce the other as being better! Many great swimmers have done well with both. I continued with my thumb out not actually investigating whether there would be some differences. What is interesting from a little research is how the positioning varies at different stages of the pulling phase.
So this is the issue when it comes to swimming, all we have is to look at the fast guys and watch what they do. Often we forget to ask could they be quicker? Swimming is interesting in that it is incredibly hard to measure in terms of bio mechanics. There are so many fluctuations and deviations with each repeated movement. Unlike a pedal going around in a circle our arms do circle but with so many shifts & deviations from stroke to stroke.
Nathan Adrian, IN at the front, OUT at the back but does fluctuate.
Katie Ledecky – seemed IN throughout. Not ideal footage but I found this to suggest a late OUT right at the back of the stroke!
Ricky Berens, OUT throughout.
Ian Thorpe– predominantly IN at the front and OUT at the back. Interesting variation which was reproduced repeatedly.
Just because some Olympians do it a certain way should not stop us from trying the opposite of our usual. When I tried to close down my thumb space my hold and balance improved. Previously I was a little wide and too much S pull. If you think about this logically it makes sense that to maximise the largest surface area and not allow any water to slip through the thumb should be in.
Previous Thumb Out Thumb Now In
Self Discover. Watch, learn, replicate but test and measure, see which is better for you. Some of the subtler, smaller movements might at first seem inconsequential but another stroke per 25 is good free easy gains. It will be pretty easy to get some measurements and decide which is better for you