In swimming measurements, do you know the difference between seconds per stroke and strokes per minute? Or the difference between tempo and stroke rate? Or when to use one over the other?
Don’t worry if you don’t know, or don’t care. But sometimes the question comes up: which one do we use and why?
The short answer is that the two terms are just mathematical inverse of one another (flip one over to get the other) and in some swimming situations it is more convenient to use one rather than the other.
Tempo = 1/SR or SR = 1/Tempo
Defining The Terms
First, let’s define some terms:
Tempo = number of seconds per stroke**
On the Tempo Trainer this is found in Mode 1.
Stroke Rate = number of strokes per unit of time
Stroke rate is most commonly measured in units of minutes…
SPM = number of strokes per minute
On the Tempo Trainer this is found in Mode 3. Stroke Rate is the same as what musicians refer to when using a metronome, to play a song at a certain strict Beats Per Minute.
In pool swimming, when doing simple speed math, it is easier to use stroke counting (which we call SPL = number of strokes per length) and tempo because these allow fo the quickest calculations in terms of pace for a length of the pool.
Pace = SPL x Tempo
In the pool, there is a turn at the wall and a push-off to the first underwater stroke, where no stroking is happening, so that distance and time has to be taken into consideration when we want to use this equation to calculate one of those variables. I won’t clutter this post with all that right now.
If we see a swimmer going along in a pool and we wanted to estimate tempo, we can time their length (subtract some seconds for the pushoff) and count strokes, and use the equation Pace/SPL = Tempo.
Using Stroke Rate
However, in open water, there are no walls, so it is not easy to observations precise distance and make calculations for tempo or stroke length. Instead of using tempo it is easier to use stroke rate, or more specifically SPM. To get the swimmer’s SPM just set the watch timer for 30 seconds or 60 seconds and then count the number of strokes they take in that time. If counting strokes for just 30 seconds then multiply that count by 2 to get strokes per minute.
SPM can still be observed in pool swimming, but since the pool length is often short and the swimmer fast enough to reach the wall before 30 seconds, you may need to count strokes for 15 seconds then multiply that number by 4.
It seems most common to hear commentators for open water and triathlon describe swimmer’s strokes in terms of SPM and not tempo.
But if you are training in the pool and into using metrics for stroke count, stroke length, precise and consistent timing of the stroke and pace, then tempo seems to be the far more convenient term to work with. And, because the Tempo Trainer has Mode 1, we can move from using tempo in the pool to open water and keep the exact same settings.
Converting Between Tempo and SPM
If you happen to like switching between the two, or need to convert a commentator’s terms into your own, here are some examples of how to convert from from tempo to SPM and from SPM to tempo.
A tempo of 1.20 seconds per stroke would be 50 SPM. 60 seconds / 1.20 = 50
A tempo of 1.00 seconds per stroke would be 60 SPM. 60 seconds / 1.00 = 60
A tempo of 0.90 seconds per stroke would be 67 SPM. 60 seconds / 0.90 = 66.67
A SPM of 80 would be a tempo of 0.75 seconds per stroke. 60 seconds / 80 = 0.75
A SPM of 45 would be a tempo of 1.33 seconds per stroke. 60 seconds / 45 = 1.33
Wearing A Watch That Measures
** One last little complication about tempo – if you wear a swimmer or triathlon smart watch it will count your strokes for you and give you a reading on stroke rate, or strokes per length (when the watch detects that you make a turn at the wall). But it is counting just entire one arm cycle of the arm that has the watch on it. When we work with tempo on the Tempo Trainer, we usually work with seconds per half-stroke actually. The BEEP sounds off twice during the stroke cycle; it BEEPs for each arm.
So, in the way we most commonly use tempo, when you are swimming along with a Tempo Trainer set to 1.33 in Mode 1, that is actually the time it takes for one arm to go half-way through its stroke cycle. It actually takes 2.67 seconds to go all the way around. But the two arms are alternating positions every 1.33 seconds. So tempo, in this case, refers to the seconds between the two arms switching positions, not the single arm going all the way through the cycle and returning to the starting point.
If you both wear a watch and use a Tempo Trainer, you may need to be aware of the different way those two devices are working.
Sorry to make things more complicated, but those geeky swimmers among you might appreciate it.
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