Efficiency Factor


Just wondering why TR doesnt calculate or track efficiency factor? (Normalised Power / Av Hr).

I’ve been using TR for about 4 years now so repeat many workouts and a spreadsheet of my efficiency factor for each workout seems to correlate well with my FTP and also recovery. In fact I can normally predict FTP changes by looking at efficiency factor for oft repeated rides (Pettit, Baxter etc done during rest week).

Its also a good metric in itself as max HR probably doesnt improve during training so getting more watts per HR beat sounds like something good to track.


Intervals.icu (my web app) has this and a lot of other interesting power vs HR data. Your rides need to be on Strava.


TrainingPeaks has tracked EF for me since getting a power meter in late 2016. To be honest I usually ignore it, along with aerobic decoupling, except for certain phases (early base, after a season break). I find a more reliable predictor of FTP changes is going out for a sweet spot ride and coming back to see they were threshold intervals. That and doing a hard Wed night world ride and having IF plus or minus 1.0.

When I was using Erg on the trainer, seeing a consistent drop in average HR for sweet spot intervals was a another clue of increasing fitness - for example EF going from 1.38 to 1.33 just doesn’t “pop out” to me, versus average HR dropping from 150 to 145 (and I’m a numbers guy).


Thanks for the inquiry! Knowing what we know about the inconsistency of heart rate, we feel it should be used as a compliment to your power data, but not something we can rely upon as an invariable metric. We have known of the many factors that work against gaining repeatable results from heart rate, including:

– Race nerves
– Level of fatigue
– Riding at different elevations
– Fluctuating stress
– Level of hydration
– Nutrition
– Caffeine intake
– Position on the bike
– Level of recovery
– Lingering illness
– The list goes on …

That being said, I think this article speaks most effectively to why heart rate isn’t a consistent enough unit of measurement for TrainerRoad to invest resources into analyzing that data. Instead, we’ll keep improving upon and building upon the systems we have in place to help athletes better measure improvement! :+1:

HR is a pretty good compliment to power in my opinion, but using it effectively does require some context and knowledge of yourself. So I’m a bit off put by some of TR’s positions on it, but there are free and paid tools out there for anyone interested in learning to use it.


Just out of curiosity, can’t this be said about power too?

Just like having a “bad day” in terms of HR being higher than usual for any number of the reasons you just mentioned. Does this no apply to power too? I am fairly certain that my “FTP” changes from day to day too

Happy to expand upon that! So for example, 200 watts is always 200 watts. Sure, you can have days where your performance varies, but that doesn’t change power as an objective measurement of your effort, whereas HR in response to that effort can change (and we won’t always know if that’s because of some change in fitness or if it’s because of some external factor).

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Thank you for that. I agree that the 200 watts is always 200 watts. But a persons RPE at 200 watts will differ? Some days that could be a zone 3 effort, another day it could be a threshold effort etc, Which you would feel, and your HR would differ accordingly.

So if you train with power, you will always work out with the same watt/kJ, but your physiological effort will differ. If you workout based on HR, your physiological effort will be “constant” but the watt/kJ would differ?

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Agreed. Comparing the pure measurements:

  • Power = absolute measurement and consistent data from day to day

  • Heart Rate = absolute measurement but variable value from day to day (at a minimum, not to mention within a day)

  • Rate of Perceived Exertion = relative measurement and potentially variable day to day (at a minimum, not to mention within a day)

On the surface, it would seem Power is superior. But as mentioned, our ability to hit a particular power, and more importantly, the RPE for that effort WILL likely be variable. We all know that hitting numbers in some workouts just plain doesn’t work some days, and then there’s the ones where it feels like we are destroying our prior limits.

Nothing in this area is as simple or cut and dry as we all would like. Power is great, but it is far from perfect when you consider the machine creating it (us) is highly variable in it’s own right. Despite RPE and HR having their known variability, I see real value in both.

Most importantly, I think a practical use of all three data points are worthwhile. Discounting any of them seems like a mistake to me because there are any number of reasons that any of them can be considered junk on their own, while one or the other two may be king on a given day or effort.

Like most things, it’s worth the effort to understand the pro’s and con’s of each, in an effort to take the best from each one and use it to our benefit.

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Hi Ivy,

Your comments and article are accepted but I am not sure if you grasped my point.

More specifically, I am interested in looking at my efficiency factor when -

  • I am doing an 0.5 - 1.5 hr TR indoor workout (which I have repeated many times)
  • On my bike which has a static set up

I also tend to eat & drink the same things during those workouts so most of the variables above arent really variables, and the ones that are variables are most definitely of interest (eg level of recovery and lingering illness) to my performance on the bike.

My point was that efficency factor is a good metric to bear in mind considering the other variables you mentioned as it is a “measure of aerobic efficiency specifically on low intensity aerobic rides” Joe Friel also provides more detailed reasons for this metric in the “Power Meter Handbook” which is worth a read.

So personally after 4 years of TR rides training with power and just under 1400 rides on trainerroad, I have started looking at power efficiency on workouts I have repeated many times over several seasons. Please note this isnt a big data exercise its just me logging and looking at my rides on excel. From my data, efficiency factor appears to give me a good indication of my condition at that point in time which work with the FTP tests as these are only done every 4-6 weeks on most TR plans. I assume Joe Friel also found it of use during coaching as he has included it with training peaks as a metric.

Normalised power isnt a good metric to measure your condition on a base level ride if heart rate isnt included because of the variables you mentioned above. For example, caffeine and my motivation level will increase normalised power but they also increase heart rate accordingly so dont seem to impact efficiency factor. Recovery from illness or too much TSS will drop my normalised power relative to heart rate so will reduce efficiency factor.

So for example Nates efficiency factor on Baxter (a workout he repeats many times) would give him a good measure of his condition at that point in time and an indication of the success of any experiment he was running to try and improve his performance. In my experience it would also give him an indication of whether he was due an uplift or reduction in FTP at his next test.

Anyway that was my point on efficiency factor but if you want more details on the metric have a look at Friels book or Training peaks etc.

One final comment linked in with efficiency factor is that although the TR software is excellent, one issue is that it has no ongoing measure of an athletes current (daily) condition. A TR rider may need to back off training if they are coming down or recovering from illness, have too much TSS or an experiment on nutrition isnt working etc. Therefore the athlete has to find a way to evaluate their condition (perhaps by measure resting heart rate, heart rate variability, qualitative feeling or efficiency factor on a ride) to know when to back off or ramp up training. Effectively the TR rider has to self coach in these areas as there is no TR metric for guidance.

However, I did notice Training peaks has started to link with heart rate variability software. My experience to date measuring heart rate variability is that it is a bit hit and miss as it often appears to me to be a lagging rather than a leading indicator. HRV and the best ways to self evaluate condition during training between FTP tests could probably make a good podcast topic by the way.

Anyway keep up the good work.


Thank you for digging a bit deeper into this idea, Neil.

We certainly agree that TrainerRoad can improve in this area, and have some things in the works that we think will help! :wink:

Regarding heart rate and Efficiency Factor, I think its important to speak to our goal of keeping our training tools as simple, yet effective as possible. When we created performance analytics, we wanted to focus on providing simple, yet powerful metrics in a manner that’s clean and easy to understand for the average cyclist. We try to focus on and develop tools we know will help athletes get faster, and while this isn’t to say that Efficiency Factor isn’t insightful/useful, we just don’t have plans to incorporate this metric to TrainerRoad this time.

That being said, we’re always trying to improve, and we really do appreciate this feedback on the tools you’re finding useful to get faster with. We’ll certainly pass this feedback along to the team!