Dropping In Surf Show Podcast S-Stroke Explained
Dec 26, 2022
History and recent research behind the S-stroke and how early swim science shaped techniques. Comparisons of deep catch versus S-stroke using CFD and force analyses. Practical paddling tips for surfers: when to use deep catch or S-like patterns and why feeling pressure matters. Discussion of training, biomechanics, and surf-specific gaps in the research.
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Origins Of The S Stroke In Swim Research
- Early swim research attributed propulsion to lift and described an S-shaped hand path based on 2D analysis.
- Doc James Councilman linked lift forces (Bernoulli) to elite swimmers like Mark Spitz, prompting decades of S-stroke coaching.
3D Studies Rewrote Propulsion Theory
- Later 3D computer analyses (1994 onward) showed swim propulsion is mainly from drag forces, not lift.
- Rushall and subsequent CFD studies found body rotation and drag explain much of thrust, overturning the pure S-stroke model.
CFD Shows Deep Catch Produces More Total Thrust
- A 2014 Johns Hopkins/George Washington CFD study compared deep catch (straight-through) and S-stroke in elite swimmers.
- Deep catch produced ~37 N total (19.3 N lift, 17.8 N drag) vs S-stroke ~24.5 N (18.4 N lift, 6.1 N drag).
