Sunday, January 3, 2010

Changing the Face of Swimming Technique Analysis – Part II - Stroke Frequency/Velocity Graphs

In the last blog, “Changing The Face of Swimming Technique Analysis – Velocity Meter/Video Telemetry”, I described technology now available that gives a swimmer or coach an instantaneous true view of the accelerations and decelerations of the swimming stroke. The most important feature of this technology is the instantaneous feedback swimmers and coaches receive, since everything is collected and can be replayed in real time right at poolside. After a testing session, everyone can go to practice, knowing exactly where the drag or decelerations occur in every stroke cycle, and start to devise methods to optimize the pattern. No more subjective guesswork or “theories” that simple observation alone provides. However, there is another really beneficial tool from this testing, that provides coaches a technique tool that can be used everyday at practice, using a basic stopwatch.

The tool is called a “Stroke Frequency/Velocity Graph”, and can be output from the Velocity Meter/Video telemetry. The swimmer performs a series of trials starting with slow speeds, progressing to as fast as the swimmer can go. The data is graphed yielding the optimal relationship of swimming speed to stroke frequency/tempo for that swimmer. For you math majors, you will notice that the fit of data produced an r-squared value of .9955 which means statistically, this is a highly reliable relationship, and the individualized nature of the graph can not be understated. In the following, we will demonstrate the sensitivity of this graph, and a sampling of the practical application of its use.

The Stroke Graph below is freestyle collected a couple of months ago on a Master’s swimmer that holds several world records. This graph represents the stroke rate/tempo (x-axis - bottom) and swimming time for one lap of a 25 yard pool (y-axis - vertical) for this swimmer. The solid blue line with the solid blue dots represents the swimmers “regular stroke technique.”

In addition to the basic test, this swimmer wanted to experiment with different techniques to see what effect it might have on velocity, compared to the “regular stroke technique.” The legend on the right defines the changes in technique we tried. All of these individual trials were conducted at top speed, and some were repeated a number of times to ensure the techniques were properly executed. These trials are plotted individually using different colors, to demonstrate how they compared to the regular technique.

For coaches, this information is extremely powerful because once the “regular technique line” has been constructed, experimenting with different stroke techniques can now be objectively compared, using a basic stopwatch. In addition, daily training can be constructed to rehearse the optimal stroke rate/tempo and lap time desired for competition. Depending on the race distance and pace desired, the best stroke rate/tempo can be pre-determined. Data points that fall below the line represent technique that is not beneficial, while any data points at or above the line represent a potential beneficial change. The sensitivity to changes in stroke technique using this graph is clearly demonstrated, by how the individual changes in technique fared against the regular technique line.

In this swimmers case, the optimal frequency that yielded the best swimming time consistently fell between 50 and 60 strokes cycles per minute. Even though the individual data points visually do not look far from the line, it is important to understand that the frequency number represents that stroke technique between 50 to 60 times for every minute of swimming, so the cumulative effect of even small deficiencies is significant. This reinforces graphically how subtle changes in swimming technique can affect performance, either positively or negatively, but in any case, the experimental changes were objectively defined.

This description is really an overview of the potential benefits using these graphs in daily practice. This particular swimmer has written an insightful detailed analysis on his web site. I have included a link to the site for those interested in reading more in-depth on how this type of technology can be used to make objective decisions, that can equate into real performance gains without guessing.

As usual, should you have any questions or would like to learn more, you can always contact me through the website:

Looking forward to testing your technique soon…