Recently my training partner started wearing his Apple Watch 3rd gen in the pool. It took about 6 sessions to get noticeable accurate. I’ve attached the image of 10 x 25 to failure. Holding a 13.5 second target pace (100 free) on a :40 interval.
If you’ve read everything from Rushall and other referenced research you’ll see some things that are poorly understood by both academics and coaches:
1: In the first 25, the heart stroke rate increases by 40 bpm and drives energy delivery. You can see the spike. Rate drops by 20 beats during the rest period.
2: 2nd 25: HR again increases by 40 bpm to about 155, for a total of 60 bpm increase over the 2 reps. Rate falls by about 25 during the rest period.
3: 3rd 25: Stroke volume has increased and normalized the HR. HR increases by 15 during work and decreases by 10 during rest. This instance is confirmed by literature – see link below. Heart stroke volume usually takes 2-3 minutes to optimize.
4: The peaks and troughs become more consistent. Not sure what happened at reps 6 and 7. Possible that he was beginning to feel some fatigue and made adjustments to his swimming cycle rate.
5: There may be an anticipatory increase in HR right before the set. Notice the HR begins to trend upward even though we are on the wall waiting for the clock. This is a very interesting phenomenon.
6: HR decreases very quickly after failure (stoppage).
7: 33 yo male so max HR is about 187. Even in a “hard” set to failure he only maintains about a 150 average. This is about an 81% max rate. His HR is not an indication of the value of the work. Also, higher HRs can be maintained using either continuous swims or interval training with a 1:2 work/rest ratio so the value of training sets based on HR is negligible.