In my last post I touched on some of the basics behind stroke rate, why it’s very much an individual pursuit and not a one size fits all situation. In this post I’ll show you a research paper that helps prove that the arguments against high stroke rate, that it’s inefficient for example, aren’t really arguments that hold water (no pun intended).
In 2010 Scott McLean, Professor of Kinesiology at Southwestern University, and his team took 10 college swimmers ranging in ability and put them in an endless pool set at 1:40/100m to see what varied strokes rates did to the swimmer’s oxygen uptake, heart rate and perceived exertion (RPE). The final results were quite interesting.
The experiment started by having each participant swim at their natural stroke rate. Then, using a Finis Tempo Trainer Pro, each swam at -20% of their natural SR, -10%, +10% and finally +20%. Since the pool was set at 1:40/100m each swimmer had to adjust the length of their stroke to accommodate the various stroke rates. For the slower SR, the stroke had to be lengthened and for the higher SR, the stroke had to be shortened. Each trial lasted for 1′ after steady state VO2 was verified and VO2 was measure during that minute. And to keep each swimmer from skewing the results, which percentage of their natural SR they were swimming at was kept a secret and randomized.
So let’s take a look at the results:
In this first graph from the experiment we get two bits of data, heart rate and oxygen uptake. Now if what is generally believed to be true, that of the idea that a long stroke is more efficient then we would expect to see both the heart rate and oxygen uptake be at its lowest while the swimmers were at -20% of their preferred SR and just increase from there as SR increased. But what this experiment found was most swimmers believe to be true. Each swimmer was actually more economical at +20% than they were at just a slightly slower SR of -10%, both in heart rate and oxygen uptake.
This next chart gives us the same VO2 results and matches it up to the swimmers RPE. This is where randomizing the stroke rate comes in. If a swimmer was told that they were next going to be swimming at +20% of their preferred SR then they would go into it thinking that it would be hard, thus making it hard. But by keeping this information from them each swimmer was able to go into the next trial with no preconceived notion of what to expect.
Again, just as in the previous chart, RPE increase at the slower SR and decrease as the SR increased. Even decreasing more when over the swimmer’s preferred SR by 10% and only increasing slightly when SR was increased by 20%.
During the expiration each swimmers kick rate was also tracked to see how the kick rate changed as the stroke rate was altered. As expected, the swimmers kick rate increased at the slower SR’s in order to fill the gap left by the very long stroke, dropped significantly at the preferred SR and rose slightly at the faster SR. Think about this kick rate to SR and how it applies to you as a triathlete. The longer your stroke is, the more you’re going to be kicking and the more fatigued your legs are going to be getting on the bike.
To put a nice bow on this whole experiment, most swimmers I’ve worked with tend to have a stroke rate that is less than optimal for them and would find that increasing their SR would make them more efficient and faster. This higher SR also sets up triathletes for better open water swims since while we’re open water racing, not only are we trying to keep our momentum going forward but also trying to keep ourselves from being taken off course but other swimmers and waves. A slow stroke rate not only slows down our forward progress it leaves gaps for waves to other competitors to push us off course.
If you’re interested you can read the entire experiment here.