Body speed and stroke impulse was measured for 12 swimmers. Finnish national team has been analyzing and monitoring the performance using the body speed measurements for multiple years. SmartPaddle measurements have been done in the earlier camps also, but for the first time we were able to systematically analyze the root causes for the variation in the speed.
The measurements were done in Turku, where they have a calibrated video analysis system stationary installed. The test protocol was simple: 50m swim at 100m racepace. SmartPaddle measurement was done for the whole of 50m and video recording was done for 10-15m of the 2nd lap. The measurement session was completed in 2h30min including the setup, 50m measurements, and additionally starts and turns were recorded on video.
Body speed and stroke impulse comparison was done by synchronizing the data and calculating the correlation. From the force data, the forward component was used in calculation. Video was used to validate the non-correlating phases of the stroke.
In the feedback sessions the detailed SmartPaddle views were used to pinpoint in more detail the root causes for slow-downs and the impulse gaps. An additional dryland demonstration was run with the swimmers to make the graphs concrete for them, i.e., simulate the feeling on the correct muscle action.
The tests were done for multiple strokes, but most of the data was on freestyle. A high level summary on the freestyle measurements below. More detailed data can be provided on request.
- The results correlated clearly. The example above is good example on that. The systems are independently calibrated, so the results can be considered reliable
- on average, 52% of body speed variation can be explained by the variation in forward directing force of arms
- the main reason for the non-correlating phases was instantaneously increased drag by various sources (legs spreading, breathing, slow hand during the catch, …)
- on the average, it takes 0.13sec to see the impact of stroke action in the body speed
- impulse gaps (<30% of average force) were on the average 0.14sec and for all except one swimmer they happened during each recovery
What do the findings mean in practice?
52% is a lot
speed variation is a direct measure of swimming efficiency and the result means that getting the impulse variation into control is a major issue
Force peaks are not enough
body slows down so quickly in water that it is impossible to have high enough force peaks to maintain the swimming speed. Instead the target should be to lengthen the stroke impulse
One muscle is not enough
force peaks also mean that in the kinetic chain, single muscle group is doing most of the work. Building continuation to the impulse enables sharing the load with multiple muscles
Timing is important
the slowest body speeds were during the recovery. Timing of the rotation is a key on controlling the impulse gaps. With the detailed view on force profile during the cycle enables finding whether the biggest opportunities are in the front or back of the stroke.
What happens next?
Continuation in the impulse is created by an intact kinetic chain. It is so much easier to teach the correct muscle activation on dryland that it is worth the effort. There is a set of dryland exercises developed for the purpose. The set is being tried out and developed together with our partners.
The measurements above were done when the swimmers were focused and fresh. Some individual measurements have been done to make visible the changes in the swimming dynamics over a longer distance of swimming. More systematic analysis and measurements will be committed on this.