I’ve been really enjoying the exercise physiology podcasts of late and I have been playing around with VO2 intervals and different rest times.
The PC system takes between 2-3 minutes to fully recover (depending on the athlete of course) so I wanted to see what the exhausted, or near exhausted, PC system ‘felt’ like today. It did not feel good. Not one bit.
Very challenging but I can see the benefits of it - it decreases the % of the interval being anaerobic and instead forces the body to work aerobically to produce the effort. The warm up VO2 efforts at 110% and the first interval went well as my PC stocks were fully charged. Then it was a gradual decline into some dark, dark times in the 3rd, 4th and 5th interval before reaching the Endurance component of the ride.
All in all a good little n=1 experiment. 2 minutes rest is not long enough for me at my current level as I am not able to execute the 3rd, 4th and 5th intervals in the session efficiently. I have now experimented with 2min to 5min rest periods (5min rest = 1:1 ratio) in the 5x5’s and for me, I think 3-4min is where I will land moving forward. Then I will tweak that using the concept of progressive overload once I get stronger and build up those oxidative capacities.
With all that said, my heart rate was in VO2 territory for the 3rd, 4th and 5th efforts regardless of power output so there is another lesson in that as well. As PC is exhausted, the glycolytic system kicks in and you are working aerobically etc. Lactate, or more specifically H+, builds up and the system reaches a certain level of acidosis = respiration and HR increase. So technically still hit my VO2 markers in those intervals, just at a different power output because of fatigue + lack of PC anaerobic contribution.
A solid 120min session in total - VO2 first up and then an Endurance block to finish up. Also have been reading about the benefits of doing an Endurance block after a VO2 block so there is that too. I can definitely confirm the benefits of that through my n=1 experience!