Overachieving ... On Accident?
The problem with quantifiable metrics is that they're quantifiable. It's very easy to look at numbers and regard them as indisputable. While that may be the case for the numbers themselves, the arrival at those numbers is much less objective. After re-reading the wiki on overachieving with bike intervals, I put some further thought into last night's workout and came to the conclusion that while I was mindful of the numbers, I had subconsciously overachieved.
Monday was a week 1 FTP test. Wednesday was a week 1 Vdot test. My legs didn't feel superb last night, but undoubtedly up to the modest challenge of a MS: 2 x 8'(2') @ 95-100%. About halfway into the first interval I glanced down at the lap AP and saw that it was right at FTP. My 3s average was dancing +/- 5-6W, and I felt quite good, so I held my average right at FTP and bumped the interval up to 10' w/3' rest. Onto the second interval - the bar had been set. Interval 1 felt smooth, so another 10' at FTP was the new prescription. A few minutes in, my lap AP was right at FTP, but the 3s average was now swinging +/- 10-15W. Holding the power seemed fine, but my legs were obviously not keeping a nice, smooth rhythm. I finished the 10' at FTP, then closed out with my remaining Z3 work.
Fast-forward an hour, and I'm loading the workout into TPeaks. Interval 1, VI (variability index or NP/AP) was 1.01, so I had done 10' at an NP of 101%. Interval 2, VI was 1.03, so I had done another 10' but this time NP was 103%. Doing some quick TSS math (TSS = 100*dt*IF*IF), I find that my training stress for the intervals comes out to 17.0 + 17.7 = 34.7 total. Using that same math, with a prescribed NP (say 97-98%), the training stress for the 2 x 8' intervals would have been around 25. Factor in the rest of the workout, and the 9-10 point delta seems like peanuts on the day. Now, increase the length of those intervals, and overachieve multiple times in a week. Suddenly, you're venturing into perilous waters.
Extending the intervals was a conscious decision. What was less conscious was the VI that was incurred as a result of fatigue. My average power was dead nuts, but the over/undershooting drove my NP up significantly. Luckily, these intervals were short. Mis-manage the VI for a 2-4 hour session, and you can forget about quality workouts for the next few days. Lesson known, but lesson re-learned.
Comments
Either it's just a coincidence that your VI and IF were the same for both intervals or are you confusing VI (variability index) with IF (intensity factor)? In completing your intervals, the VI for them should be 1.00. If your getting a VI of 1.03 for a 10' interval, then I think you need to be more consistent within each interval. In regards to the second interval, the VI for that is pretty significant. A fairly well executed FTP test usually only yields a VI of 1.02. If you look in the journal, what were your low and high watts for that interval?
I understand the theme to your post and agree to some extent around the accumulation of TSS over time when you over achieve on the intervals. I don't necessarily agree on the VI as many quality roadie rides will show a large VI, but still do not run the risk of overtraining. The VI to me just indicates a different type of riding where there are lots of surges followed by rest times when your tucked in on someones wheel.
I overachieve a lot on the intervals, but I feel I know myself, body, and mind pretty well being part of EN entering Year 3, and recognize when to back off if it may interfere too much with subsequent workouts. I'm brainwashed by Coach Rich's very simplistic, but accurate view of training..... fitness is in the mucles and I should be trying to recruit as many muscle fibers as possible in order to get them better adapted, stronger, faster, whatever. Therefore, in the OS when not much matters in the large scope of things I tend to push myself to recruit as many fibers as possible whenever possible.
Thanks for questioning the numbers, Keith. This is why I'm liking EN already. I have the definitions correct (VI = NP/AP, IF = NP/FTP), but started to question the numbers myself as I was writing the OP. When I got home, I pulled up WKO to look at the file, and low and behold, the file that was open was from a road ride I did on Jan 1st. I had two intervals, each 15 minutes, one with VI = 1.01 and the other with VI = 1.03 - IF on both intervals was high Z3. I recall that the second interval was on the return leg into a heady wind (i.e. lots of surges, some standing). For the sake of sanity, I double-checked last night's intervals and VI was dead on 1.0. Thanks again!