Ask the Scientist: To Glide or Not to Glide, That Is the Question

FreeTriSpeed got this reader question from Ken V. on swim technique. Do you have a question on the science of triathlon? Ask the Scientist!

“Great website and book. Your work is both technical and entertaining (hard to do!) and much appreciated.

I have a question regarding the swim. I know there are many different schools of thought on “the best way” to swim. I just have a technical question about one portion of the swim stroke–the glide. Or more precisely, “to glide or not to glide” is the question.

There seem to be two popular swimming “systems” out there that oppose each other.

Pitch of hand, swimming, swim strokes, triathlons, triathlete
ITU world champion Sheila Taormina, now a triathlon swim coach

1. One school believes that incorporating the glide reduces energy expenditure, making it easier to complete the swim, and allowing a more efficient use of the body.

2. The other school says to eliminate the glide as much as possible, claiming it reduces your momentum, forcing you to expend more energy to resume your speed with each stroke before you started slowing down during the glide. They say to basically increase your stroke rate, thereby avoiding any loss of speed, which would overall result in a faster swim and less energy used. However the pro-glide people would say that such a high stroke rate would once again increase your overall energy expenditure, slowing you down.

So my question is: what’s more efficient in terms of energy expenditure per unit distance covered in a swim? Less total swim strokes but including a glide, or more total swim strokes but no glide? Triathletes looking to lower their “energy leaks” are ready and waiting.

The obvious follow-up question which begs to be answered for all the speedsters out there is much harder to answer for sure (maybe impossible): which would be more favorable in a race? Would you tire out with the high stroke rate and end up slowing down anyway (the old tortoise and the hare theme here)? Or is it beneficial, akin to the higher RPMs in cycling and increased cadence in running that coaches love to talk about? Would you really gain more distance per stroke if you use a glide, perhaps resulting in a slower swim time but less overall energy used, which could be used for the bike and run? Tough question, I know.

Thanks, Ken V.”

Jim Gourley’s reply:

Thanks for the question! As you rightly observed, this is a complicated issue. It involves competing requirements (speed and efficiency) and a good layout of the principles at work. You’ve pretty much done all the work for me in accurately defining the problem.

With the issues clearly defined and the variables placed in such opposition, there’s only one thing left to do: collect data. Thankfully, another group of researchers thought of our problem before you and I did, and went out to collect the very data we need.

http://www.feelforthewater.com/2012/12/the-data-on-stroke-rate-and-efficiency.html

The data in that report clearly indicates that there is in fact a higher energy cost associated with a lower stroke rate. This is due to the energy required to hold the body in correct position as the arms slow down. That’s not something that could be predicted without experimentation, which is why direct observation is so important.

swimming, swimming stroke rate, swim cadence, triathlon, triathlete

It’s also remarkable that trained swimmers’ preferred stroke rate seems to be almost the most efficient, or just a little less than the optimal condition. After accelerating their rate beyond a certain point, the energy cost increased again.

There are a few tri-specific conclusions we can draw from this:

  1. First, your energy cost will probably increase even more than the swimmers in this study due to open water conditions. A high stroke rate is even more important to you due to the turbulence and destabilizing obstacles (i.e., other people).
  2. Second, keep in mind that these are trained swimmers, and most triathletes (according to data) are not. Your personally-selected stroke may or may not be the most optimal for you due to technicalities in your form.
  3. Finally, we can reasonably conclude that training will increase your VO2 and therefore allow an increased stroke rate for greater speed with lower energy cost. This training does not necessarily have to be swimming.

Hope that helps and good luck in your training and racing going forward!

Do you have a question that’s always bugged you about swim-bike-run? Ask the Scientist!

FASTER by Jim Gourley

Jim Gourley is an astronautical engineer and triathlon journalist who has written on the science and technology of triathlon and cycling for Triathlete, Inside Triathlon, LAVA, USA Triathlon, and 3/GO magazines.

His new book FASTER takes a scientific look at triathlon to see what truly makes you faster—and busts the myths and doublespeak that waste your money and race times. With science on your side, you’ll make the smart calls that will make you a better, faster triathlete.

FASTER is now available in your local tri shop or from these retailers:

FASTER is published by VeloPress, leading publisher of books about triathlon. See more books for triathletes at www.velopress.com/category/triathlon.

 

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4 thoughts on “Ask the Scientist: To Glide or Not to Glide, That Is the Question

  1. Thank you so much for the info! It really cleared things up. I plan to use the data to improve my speed so I’m not such a destabilizing obstacle myself!

  2. Please define “Glide”….
    Nearly every Olympian or elite swimmer you watch footage of has an element of reaching forward and extending…Is that what you are defining as “Glide”….
    rom what I have observed… most people who have a velocity drop on the forward extension, really have a problem with the recovery arm not coming forward fast enough….
    I don’t see this as a “Glide” problem but more of a delayed “Recovery Arm” problem…

  3. Adding to Peter’s reply above: You note “the data in the [Swim Smooth] report clearly indicates that there is in fact a higher energy cost associated with a lower stroke rate. This is due to the energy required to hold the body in correct position as the arms slow down”.

    Did you arrive at this conclusion (slower stroke rate = more energy) based only on this data, or did you seek several sources, including your own observation and experimentation that support this conclusion? And if so, what other source(s), observation(s), experiment(s), etc.? Second, as part of your conclusion, what specifically is using the energy (i.e arms, legs, spine, etc) associated with the lower stroke rate?

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