Scientists from Tokyo and Ibaraki discover there’s a cutoff point where kicking actually starts to slow you down.

Part of what makes swimming such great exercise is that it’s a whole-body workout. Especially if you’re swimming crawl (a.k.a. freestyle), you’re using your arms to stroke the water, your abs to rotate your core, and your legs to kick for added momentum.

Except, according to researchers in Japan, all that kicking might actually be slowing you down.

A team of researchers from Tokyo Institute of Technology and the University of Tsukuba (in Ibaraki Prefecture) recently performed an experiment. They had a swimmer hop into a water tank and swim crawl in two different ways, first by stroking with his arms and kicking, and next by using his arms without kicking. Then they measured the amount of drag/water resistance, and discovered that whether or not kicking is actually helping you move forward depends on the speed at which you’re swimming.

Specifically, if you’re swimming at a speed of 1.1 meters per second (which would allow you to swim 100 meters in 90.91 seconds), go ahead and kick. At that velocity, the kicking is having a positive effect on your total forward momentum.

However, if you’re a sufficiently speedy swimmer that you’re moving at 1.3 meters a second (or 100 meters in 76.92 seconds) or faster, the researchers found that kicking disrupts your body’s ability to glide smoothly through the water, and the increased drag will slow you down.

Now before you track down your swim school teacher from your childhood and yell at him for lying to you, there are a couple of things to keep in mind. First, a swimming speed of even 1.1 meters per second is pretty quick for an amateur athlete (average adult swimming speed is said to be around 0.9 meters per second). Second, the researchers were purely concerned with which technique produces more speed, not with which provides the better workout and fitness benefits. And finally, the experiment only examined the crawl, meaning the effect of kicking could be different for the breaststroke. Backstroke, and butterfly.

Still, if you’re a high-level competitor looking for freestyle victory in the pool, the experiment shows it’s better to let your arms pull you to glory, and just let your legs be along for the ride.

Sources: Asahi Shimbun Digital via Hachima Kiko, Journal of Biomechanics, Chron
Top image: Pakutaso

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