Desire to improve fitness

I want to improve my overall level of fitness. VO2 max seems to be a reasonable way to measure this. A proxy for VO2max is a fitness test over a specific length of course. For example running a mile. For the test to be useful it needs to be repeatable and give consistent results over short periods of time. After an initial few attempts the typical time on the test needs to settle down to be reasonably repeatable.

I am cycling from my house in Glasnevin to Sutton and back as my test route. I have been repeating this route mainly for training rather than testing for quite some time now, but have only been serious about improving my times since about 4 months ago.

Reasons

I have never been a competitive athlete, but decided to see if I could improve my fitness more systematically than I normally do. I found that when I attempted the test/training route my times settled out at about 1 hr 8 mins with some variation. In particular I noticed that on the days that I did this cycle (or a longer route) I was very low on energy for a good part of the rest of the day. I typically cycle in the morning at the weekends. I am curious to see if I can reduce this level of energy depletion as I get fitter. In other words will I be able to do a hard workout of a reasonable length and intensity and not be as tired over the course of the rest of the day.

To do this I need to get fitter - fitness of this sort is really the ability of my cells to respire. Better aerobic fitness is less about heart and lung fitness than about my bodies ability to make use of all of that oxygen and fuel.

https://peterattiamd.com/how-does-vo2-max-correlate-with-longevity/

method

progress so far