Letters to the Coaches: Power vs. Heart Rate and More

Hi David

I am looking at following the 80/20 ironman training plan (probably level 2) and have downloaded the free Ironman plan

I have a few questions:

1. When cycling I noticed I can keep in zone 1-2 for heart rate but when I analyse I see my power is spread more over all zones including 4-5. Is power a better measure and more preferred way for cycling?

2. What kind of performance gains would you expect during a 4 week period? If there is no improvement in pace and power would that indicate an issue in my training?

3. Does the plan contain longer cycle and runs towards the end of the plan?

Thanks, C

Dear C,

Thanks for looking into our plans! Responses below.

1. Power is commonly recognized as a superior way to measure intensity. Heart rate (HR) is affordable and convenient, but HR has several disadvantages. The root of these disadvantages is that HR is an indicator not an output. Like your car, your engine temperature (an indicator) might be directly related to your horsepower (output) and speed (outcome), but often they are not in sync at all.

Your power zones are also most likely not yet calibrated correctly, almost certainly too low. Consider our Intensity Guidelines for Triathlon document for some protocols on how to retest your power zones.

2. This is tough to answer. I regret that genetics plays such an out-sized role that the results are all over the map. What I can comfortable say is that the best athletes in the world use an 80/20 intensity distribution, and you’ll have the best chances of success with that format. If I were to commit to a “typical” triathlete without a strong background in cycling, I often see a 10-15% percent improvement in the first year, another 5-10% the second year, and diminishing but continued returns from year 3-5. The monthly improvements would be some fraction of those annual estimates. Genetics could double or half those “typical” results. Be patient, sometimes you’ll go months without seeing an improvement, and then you’ll get a 5% bump overnight.

3. Yes, the free plans are just the first two weeks of each plan. We use the empirically proven method of progressive overload in all of our plans, the weekly volume caps out at 2-3 times what you see in the first 2 weeks.


Matt and I periodically publish anonymously your inquiries to us, particularly when the answer may benefit the community. Have a question about 80/20 training or training in general? Feel free to e-mail me. David W.