The Vertical Line

by SwimSwam 5

November 27th, 2017 Training, Training Intel, Video

Courtesy of Jozsef Nagy

About Jozsef Nagy

Nagy was born and raised in Hungary where he won the 1973 Hungarian Jr. National Championship and continued to compete for Hungary afterward. Nagy may know more about the breaststroke than anyone else in the world and was a breaststroker himself. His talent as a swimmer and thereafter application of physics to the sport of swimming, he created the “wave-action breaststroke” bringing him to fame.

Briefly about the Background:

The idea first crossed my mind in 1994 during practice analyzing technique. It was finally implemented in 2010. At that time, I was working in the Vancouver National Swim Centre where Allan Wrigley, the expert in biomechanics at the Canadian National Swimming Team, helped our everyday trainings. I shared my idea (which was at that time already 16 years old) with him and he promised me, without hesitation, to work on it and come up with a solution. It was done in a year!

In swimming, as well as in other sports, steady speed is the most efficient way to move forward. It is even more important within one stroke than for the entire distance. The change of speed within a stroke is very visible especially in breaststroke. We, coaches, would like to see, measure and control the steadiness of speed, or the lack of it, as much as possible. This need brought up the whole idea.

The idea is to shoot a few seconds long video with a standing camera about one full stroke of a breaststroker. That way the swimmer swims in and out of the picture. It can be easily timed how long and how fast this one stroke is and thus we will know the speed of the swimmer. Then, with the help of a computer program a vertical line is applied on that short video. The program allows us to set the speed of that vertical line freely. Best is to set/fix the line on the hips since they are the closest to the center of gravity of the body. It can be set, of course, on any other part of the upper body or even on the head.

If the speed of this vertical line, hereinafter “VL”, is set according to the average speed of one stroke of the swimmer, it will be clearly visible where the swimmer’s movement is faster/slower within a stroke.

It will be even more visible if we slow down the video in synchro with the VL. Then comes the beautiful task of examining/finding the reasons why that speed change within one stroke occurs. Swimming faster than the average speed is usually not a problem. So, we should rather focus on what causes the loss of speed of our swimmer.

And then comes the even more beautiful task of correcting these mistakes!

What can be the VL used for?


  • As mentioned before, to discover the mistakes that alter the speed of the swimmer within a stroke.
  • To try different techniques, and to compare their impact on the speed within the stroke.
  • In breaststroke, in the underwater pull after the start and the turns, we need to be aware of several points where the swimmer can potentially lose speed. These could be made visible and possibly corrected by the VL.
  • When is it worth to start the underwater pull compared to the speed of the underwater stroke?
  • Is the dolphin kick worth to be done before the pull out?  
  • Is it worth to glide after the pull out before bringing the hands and arms forward? if yes, then for how long?
  • By the means of applying the VL it could be made visible how, and to what extent, the different ways to bring the arms forward slows down the swimmer and how the pull up of the legs effects the swimmer’s speed.
  • We can see how the timing of the pull up of the legs effects the speed of the swimmer. It will also be visible how the different timing of the pull up of the legs effects the speed compared to the VL. But above all the most visible and measurable impact of applying the VL is how the different angles created by the thighs and the horizontal line effects the speed of the swimmer.

Fly, Backstroke and Freestyle

Differences here should be handled in a lot more sensitive way, since they are certainly smaller than in breaststroke, especially in the case of freestyle and backstroke. The VL could be a significant help in deciding when to start and stop kicking after the start (max. 15 m) and after the turn in these strokes.

With the help of the VL it can be a lot easier to decide when to start kicking after the glide. Or to see when the swimmer slows down to the maximum speed reachable with kick after the dive and turns.

Since the VL can be set on the expected speed in a race we could exactly see for how long it is worth to kick underwater.

At the same time, for how long the swimmer can keep a higher speed with the underwater kick than the speed of his/her actual swimming speed. For most swimmers, the last two kicks are usually slower than the strokes coming afterwards. So, those two are unnecessary or even ….

It’s worth to take the pictures (depending on the transparency of the water) from as far as possible (with zoom) because if we want to time the stroke of the swimmer with high accuracy we must not ignore the distortion.

A 3-meter-long stroke filmed from the distance of 20 meters, captured with a standing camera, means that the middle of the stroke is 20 meters away while the beginning and the end of it is 20,056 meters from the camera.

This difference of less than 6 centimeters does not affect in a significant way the speed differences between the stroke and the VL. If, however, the video is taken only from the distance of a couple of meters the distortion can be more significant.

Based on my experience with the VL I can highly recommend it to anybody. Since almost each swimming club and national team has computer experts available, setting up such a program is possible these days for anybody.

Finally, I would like to show how it looks like in practice.

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3 years ago

What do I buy? How much? I want it.

Reply to  Anonymous
3 years ago

It doesn’t look like Mr. Nagy is trying to sell a product. He’s just sharing a concept. As he said, this would be relatively simple to make, and you probably wouldn’t even have to make it from scratch as I’m sure some modern video editing software could be utilized for this. Might take a bit of trig knowledge, but overall this is pretty simple.

3 years ago

Can I get any screen shots of the program, please

3 years ago

At the bottom it says he’s going to show us this approach in practice. Is there supposed to be a video? Did I just miss it?

Reply to  Stoyle
3 years ago

From a video editing point of view I can see a number of ways to do this manually in Sony Vegas. Easiest way I see of doing it is with a line moving across the video at the average speed of the stroke and playing slowly to spot the points in the stroke where the swimmer gains or falls relative to the line.
I’ll steal some footage from TRC or GoSwim and try it now actually