pretty geeky evening. However, upon checking my emails I was relieved to discover that at least one other person was engaged in an equally geeky activity. Tim had lent me his heart rate monitor during our last DNF training session and on Sunday evening I received an email attaching the graphs he’d created on his computer.
If you read the previous post, you’ll know that last week at London Freedivers I joined Tim and Nick in their punishing (at least for me) DNF training. The graph below shows my heart rate over the first exercise, which involved 10 repeats of 33m DNF, leaving every 1min 30seconds. This means that the slower you swim the length (helping you to relax and conserve energy) the less time you have to recover before the next length.
Graph 1 - CO2 DNF Table
The next graph is a DNF swim of about 50m, which I did with at the start of the session. I had contractions quite early and came up 4 strokes after the first contraction.
Graph 2 - 50m DNF
Unfortunately, I don’t know the exact time I started and ended the dive, so it’s a little bit difficult to draw conclusions. Bearing this in mind, I find the following points most interesting:
1. As you can see, my heart rate drops by 70bpm during the dive! It’s very cool to be able to see the effect of the dive reflex in pictorial form. If I remember correctly, I had a 3 minute breathe-up before the dive.
2. The graph shows that my heart rate is lower at the beginning of the breathe-up than it is at the end! This is at odds with what I would expect; I’d expect a gradual lowering of heart rate during the breathe-up and then a slight peak caused by stress immediately before immersion. It looks like I need to review what I’m doing for my breathe-up.
3. My heart-rate is elevated before the breathe-up even begins. I just measured my resting heart rate on the inside of my wrist sitting in the café and its 69bpm. Even this seems a bit high – I’m going to blame it on my lack of aerobic fitness (or on the hottie sitting at the next table reading Hemingway). Assuming immersion occurs just before 03:20, my heart rate is nearing 90bpm at the start of the breathe-up and it rises to 115bpm immediately prior to immersion.
4. Assuming (again) that I end the dive at approximately 03:21:20, there is a subsequent leap in heart-rate within a very short space of time – surely this can’t be good for you?!
OK, I have to rush off to training at London Freediving now! Harry's down in London doing a placement at the London Diving Centre and will be training with us tonight :). If anyone has any comments on the graphs, I would love to hear them...
