n=9, three genres, 27 treadmill sessions, one heart rate monitor that kept falling off.
Everyone has a theory about what to listen to while exercising, and every theory is held with a confidence that the underlying evidence does not support. I decided to test mine on other people, which is the only ethical way to be wrong.
Written before any data was collected, and reproduced here unedited, because a protocol you are allowed to revise afterwards is not a protocol.
Hypothesis. Tempo above 140bpm produces a measurably higher average heart rate during steady-state treadmill running than tempo below 100bpm.
Protocol. Nine volunteers, three sessions each, 20 minutes at self-selected pace. Genre assigned in rotating order. Heart rate sampled every 5 seconds.
Falsified if. Mean heart rate difference between the high and low tempo conditions is under 3bpm.
The mean difference was 1.4bpm. The hypothesis is falsified by the criterion I wrote down in advance, which is an annoying thing to have done to yourself.
Self-selected pace turns out to be the entire story. People ran at the speed they were going to run at, and their hearts responded to the running rather than to the music. Two participants independently described the fast condition as "stressful" and then ran exactly as fast as before.
The chest strap fell off four times across 27 sessions, always on the same participant, always during the third song. I have excluded those intervals and noted here that I have done so, rather than quietly trimming them, which was tempting.
The data is in the linked sheet. If you find something in it that I missed, I would genuinely like to know, and I will say so here.
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