I have been running for a few months (34m), and I can feel I have become more fit when it comes to how I feel and achieve while running. Now my session is more than double the time than when I started, and even when I end it, I would still be in zone 2 as my heart rate and breath rate are lower, unlike when I began running and I would always find myself at zone 4 by half the time (similar pace). Even when I try to run faster, I can do so for longer than before.
Yet, my VO2 max has dropped from 39.8 to 37.8! I would get very surprised every time I see it drop. Why would that be?
I’ve been increasing my running over the last 4 months. Most practice runs are slow, zone 2, heart rate 125. Sometimes I run the first 5k fast or mix it up by HIIT runs. The watch says my VO2Max has consistently increased and my last practice run, 5 days ago, hit a new personal high. 4 miles. So then two days ago, I’m at an actual 5k run, which is only 3 miles. I go all out, heart rate 157 average, time significantly faster than practices. My VO2Max goes down.
I know it’s just an estimate, but this peeves me. I have two theories:
distance matters. The real race was shorter so I get less credit.
Race speed went up, but heart rate went way up. So maybe it’s like in a car if you increased the RPM of the motor but the car speed didn’t go up linearly. Like the transmission is slipping.