First Ride Report

First ride report. Well, second ride...the first was 20 minutes last Saturday to make sure my bike still worked.

I bought a new PowerTap wheel and handlebar computer head. I used one from 2002 till I quit, and sold the setup to some nice person on Slowtwitch. It was the old wired setup, and the new one is wireless. Very nice.

So, some observations and some backdrop for using power in cycling.

First, I am an unabashed fan of using power output as the key effort measurement in cycling. (Likewise, I use pace in running.) I wear a HR monitor from time to time for cross-checking my perceived effort, but power output is what matters.

I am also an unabashed fan of the "normalized power" paradigm developed by Dr. Andrew Coggan. You can google "Coggan normalized power" to find the details on the algorithm. The notion is that increasing power output does not linearly increase the stress or load on our metabolism, but rather increases that load to the 4th power of power increases. IOW -- going 5% harder is (1.05^4)-1 percent harder, or 21.5% harder. At very low efforts (toodling around town), you might not notice it so much. But in racing and training conditions, it makes a big difference. Within a given ride, we have periods where power is high and low ... what is the best way of evaluating these into an "average?"

So, for purposes of evaluating a workout, I will record not the mathematical average power (AP), but the normalized power (NP). In a very real sense, AP is "how fast did I go" and NP is "how hard did I ride." And training adaptations arise from "how hard did I ride."

A further extension of the NP construct is to relate NP to "threshold power," defined as power that could be held in an all-out 60 minute effort (P60). The ratio NP/P60 is the relative intensity of the workout -- "intensity factor" in the jargon, or IF.

Finally, we know that training stimulus is a factor of both the intensity of the workout, and its duration. Leaving out the "why" (google it), multiply the square of IF by the duration (in hours) of the workout, and we get the training stress score, or TSS. Keeping track of TSS on a day-to-day basis is a proven way to manage training stimulus and recovery. I'll skip the details on that...it's all out there if you want to explore more.

A key benefit of using TSS is that it allows an athlete to relate, say, a long steady ride to a shorter harder one. A 90 minute ride at a relative intensity (IF) of 90% has a TSS of 122.

A 120 minute easier ride at an IF of 78% also has a TSS of 122. Interesting. What we are saying here is that these two rides are roughly equivalent in terms of training stimulus and stress. If you only have 90 minutes, ride at an IF of 90 instead of 78 and you'll get a workout roughly similar to the 120 minute ride. This is not the only consideration in structuring your workouts, but it is near the top.

I don't think that the TSS construct does a good job of "equalizing" intense short-interval sessions, such as a sprinter might do, with the longer efforts that a triathlete or 40k specialist might do. But within the confines of reasonable triathlon bike training, the TSS paradigm just flat-out works. More than a decade of real-world application has proved it beyond any doubt. It works.

So, back to my ride...I rode 1:05 at an NP of 162 watts [EDIT: I later learned that I had not "zeroed" out the powermeter. The ride was likely under 150 watts]. I can only estimate my FT at this time, but if it's 180 watts then my TSS was just 87. Not much of a training load, but I gotta start somewhere.

Of more interest is that my AP was just 144 watts. As said above, NP is "how taxing was the ride" and AP is "how fast did I go." In an ideal world, AP=NP so that we get as much speed out of our metabolic effort as possible. AP will move lower and lower relative to NP the more variably I ride. We call ratio NP/AP the variability index, or VI. Generally speaking, a VI above about 1.03-1.04 is costing a rider speed. My VI on this ride was 1.13 -- downright horrible, and an indication of just how much my cycling skills have eroded. It takes experience, practice and focus to keep VI down on a rolling terrain ride. I will need to regain those skills.