Can you imagine, back in the day, before heart rate monitors and powers meters, way back when you had to do things like use a stop watch? How could you possibly pace? Speed? But what about things like wind, air density, etc...
Now-a-days, I contend that speed doesn't matter.
I can simply look at my improvement based on power and weight. Granted if I am competing on a TT bike, which for Ultra that's basically it (Ill argue in a separate blog why your weight and climb bike don't matter for most Ultra events), position and CdA matter a whole lot. Assuming the same TT position and setup, I can pace solely based on power and let all the other numbers be what they are. I may be fast or I may be slower, but really pacing by power is the only way to go.
If I want to test new equipment and its aerodynamic affects, yes then I will run a closed loop course and see if it is faster or slower. Other than that, I am not concerned with speed, but purely power. One thing to note is the affects of altitude on power. I always calibrate my power down or up based on altitude. Our friends over at Training Peaks have made this beautiful chart which I have found to be extremely accurate.
I also think that it is imperative to adjust your FTP in your training software anytime you have an altitude shift.
Here is my argument:
Assume you go to 3000 feet and your normally acclimated at sea level. This shows about a 5% drop in ftp.
Simply looking at the numbers, a person can typically hold 105% FTP for about 20 minutes max, but they can hold 100% FTP for about 45-60 minutes.
So that small amount of 5% makes a HUGE difference. One way to account for this if your doing a lot of up and down, is to simply run a heart rate TSS score, you can do this in training peaks by clicking the arrow next to your TSS and selecting HrTSS. Obviously you must track heart rate on your ride.
Pacing by heart rate? Yes this can possibly work, if your racing 12 hours or less. Lets talk about heart rate drift. Most cyclists think of heart rate drift as something where your heart rate drifts upwards as you get more fatigued. For example, jump on the bike and hold 90% of your FTP, you will see your heart rate slowly drift upward over the next 30 minutes of holding that. In Ultra Cycling we typically tend to see the heart rate drift upward as described above, but then after about that 10-14 hour mark the heart rate drifts downward. So no matter how hard we push the heart just can't get up to speed. Too much fatigue. To pace by HR may not work in cases over 12 hours.
I wanted to keep this blog short, but I think I opened up a few cans of worms which I will have to finish unpacking later!
--Shane (The Fat Cyclist)