63:51 for 4000yds. Compare with my December 18 result two months ago: 68:19 for 4000yds. This is pace for a 67.5 minute Ironman swim. That’s a 6.5% improvement in my TT pace over the course of the last two months, and a whopping 14.3% over the course of the past 3 months which is my first datapoint doing 4000 yard TTs and corresponds to the beginning of when I started the increased focus on swim this winter. I had a quite strong negative split, -1.3% decoupling, but that’s partly due to me making a relatively significant effort increase during the second half. I wanted to make sure that I was going to finish my 4000 feeling absolutely confident that I had swum my fastest TT possible. The variability in this result is more consistent across the hour compared with that previous result and indicates that I didn’t loose focus at any point in the swim.

The keywords I was focusing on were to make the kicking count, and to swim with momentum. The first is to directly combat my tendency to only kick hard enough to maintain an acceptable body position. I’ve started to realize that my body position through the water is actually better when I’m kicking for propulsion rather than just kicking for body position. Like most aspects of triathlon it’s one of those things where when you work harder you go faster, but I’m starting to feel like there’s an efficiency improvement as well, so my return on investment for that effort is something I’m starting to consider worthwhile. The second is based on feedback from Erin, that I have to work pretty hard to get back up to speed every time I loose some of it, and that I’m best off to just keep the bits of speed that I’ve got. Right now that means two things for my swim stroke: 1) ensuring that I am not afraid to keep the arms moving, if I back off the arm-speed and focus more on getting long strokes excessively I am speeding up and slowing down with every stroke, an incredible waste of energy. 2) that after I push off the wall I’m going faster than swim speed, if I coast down to below swim speed before swimming I’m wasting energy, I’m best off to give a double kick and take a stroke before even thinking about breathing. Taking that first breath doesn’t break my body position in the water as much if it’s a mid-stroke breath, and hence I don’t loose that momentum.

The trendline is a per-kilometer average pace.