New Beginnings Await You Every Moment But Should Your Hands Be Open Or Closed In The Swim?


Hi folks,

Springtime is a new beginning for the Biosphere, so here are some spring plants at Souther States in Chapel Hill, NC.

Springtime is a new beginning for the Biosphere, so here are some spring plants at Southern States in Chapel Hill, NC.

Remember that old Louis Pasteur quote, “Chance favors the prepared mind?” Well, it is most certainly pretty accurate when it comes to biological research, but I also think that it is true for athletics. That is why I try to learn new things when I can, but I make sure to solidify what I have learned already, as I don’t want to chop and change all the time. This is not an easy call! One thing that does help me learn new skills as a triathlete is to train with, and study the biomechanics of, better athletes, which includes my new swim coach and friend, Rick Fee. This guy is way faster than me and he seems to make no effort as he swims, but he awaits me patiently on the wall and sets our intervals for my glacial pace (thanks, Rick). So I watch Rick, in the same way that I watch my son Duncan (also coaching me) as he runs. Today I noticed that Rick has his fingers slightly open during the power stroke, and that interested me a lot. A classic fluid mechanics question.

If you use hand paddles, up to some maximum size, they do make you go faster, whilst giving your upper body extra strength training and improving stroke mechanics. This is probably because they make your hands effectively larger. Now we come to the fluid mechanics of open versus closed hands. Let’s think about it.

What do we know or think that we know about the physics and what are the questions that we need to ask of the system (hands of varied openness during freestyle swimming)?

  1. Much of fluid mechanics is non-intuitive making computational
    The relationships between pressure drop, flow rate, and pipe diameters is fascinating.

    The relationships between pressure drop, flow rate, and pipe diameters is fascinating.

    fluid dynamics combined with laboratory experiments the best way to find the answer to complex flow problems, neither of which are readily available to me anymore.

  2. Bigger paddles, up to some optimal size, will make you go faster in the pool, and as you open your fingers your hands become bigger but leakier paddles.
  3. No water will flow through a very tightly closed hand and lots will flow between the fingers of an open hand, so what is the ‘effective surface area’ (size of paddle) of opened hands with varying degrees of openness?
  4. This becomes, in part at least, a boundary layer problem. For instance, water on the surface of your hands that is not stirred (stuck because water molecules are little magnets that line up) is not available for convective flow, so opening the fingers just two times the thickness of this boundary layer should be the same as a closed hand, but this would be very little opening indeed, and is probably trivial for the problem at hand (excuse the pun).
  5. Closed hands will have essentially two (one for each lateral margin) major series of shedding vortices (whirlpools) behind them, which influences the effective size of the hand, but open fingers would provide a whole series of such whirlpools, and who knows what that will do to the pressure drop (effective hand size) of this more complex paddle.
  6. Changing hand opening will affect perceived effort by the swimmer, making it difficult to compare data from open versus closed hands, so basically this is a very difficult scientific experiment to carry out correctly.
  7. There are many other variables that could be considered, but this will do for now!

Based on my backgrounds in swimming and fluid mechanics, I suspect (for what that is worth!!!!) that there is an optimal and non-zero degree of finger opening for maximal propulsion, assuming all other aspects of your stroke are equal.

All of this is great in theory, but the clock will provide the real test. It is a fact that Rick swims much faster than I do, but the real question for me, as I try to chase him down, is whether his open fingers contribute to our respective speed difference in the water.

Thoughts out there or better still experimental data?

-k @FitOldDog

Today’s workouts:

Workout PLAN Coach: Chris Hauth
Duration: 03:00:00
steady Z2 HR/watts ride


  1. Luis Torres says

    Thanks for your Knolowedge. Totalemnte de acuerdo yo he cambiado de la mano cerrada y tensa (con el consiguientes waste of energy) a una mano relajada y con los dedos ligeramente separados y voy mejor.

    Saludos fron Spain

  2. Salud Luis,
    ligeramente separados, esto de acuerdo, pero yo no escribo Espanol muy bien. Desculpe me! Mi hermana puede ayudarme, espero.
    Muchas gracias por tu comentario.

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Disclaimer: As a veterinarian, I do not provide medical advice for human animals. If you undertake or modify an exercise program, consult your medical advisors before doing so. Undertaking activities pursued by the author does not mean that he endorses your undertaking such activities, which is clearly your decision and responsibility. Be careful and sensible, please.