Power vs HR zone training

I'm stealing a line from someone but it always makes sense:

Power (how much force you apply to the drivetrain) is an input, heart rate is an output.  There are also a ton of variables that go into heart rate like how much you slept, what you ate, how hydrated you are, how hot it is, etc.  That's why HR can be a hard metric by which to gauge performance from day-to-day and from workout-to-wokout.  It's not consistent.  But it's a good race day indicator about how your body is reacting to the work you're doing.

You can ride a ton with both a power meter and a heart rate monitor and pour over the data and see if you can find some translation.  Maybe you find some translation, maybe you don't.

Plenty of folks riding with power during the winter with TrainerRoad or something similiar and then correlating power to HR once outside again.  Just need to be willing to adjust/compensate for effort level indoors to outdoors as well.  And FWIW, many only train with HR and can be very successful with it.

It doesn't necessarily need to be an either/or proposition.  An effective approach can be to train with virtual power using Trainer Road or similar from now until the first of the year, focusing on increasing your FTP (functional threshold power), collecting HR data alongside the virtual power.  Then, begin race-specific training using HR.

GMAN, where did that come from? Notably different from what I've seen. Curious if the context mattered.

And back to the OP, are you asking about a conversion factor to change the HR data you collect into power? That wouldn't be any more helpful than HR itself as they'll all be based on HR in the first place. If you don't get an actual powermeter, you could try virtual power on the trainer and watch your HR there.

I should've elaborated more but I was posting from my smart phone and didn't feel like typing anymore than I already had.

Power is both an input and an output depending on how you want to look at it.

It's an input if you think about it like I mentioned... the amount of force you're applying to the drivetrain.  It's an output as well... that amount of force produces a certain number of watts.  Your heart rate is strictly an output kind of number.  I'm trying to find the exact quote but I can't recall whether I read it here, on ST or at EN.

What I've seen best was from Jordan. And that was power is an output. HR is an indication of an output, but not quite a direct output. I haven't thought so much on parts of the power being an input, so will let that thought think is some before saying anything.

You absolutely can do it, but it does require a small hardware investment.

If you have a trainer, and do the bulk of bike indoors, you can get power estimates that are pretty good for power-based training using software like Trainerroad (costs), perfpro (costs), veloreality (free), and the new Maximumtrainer (free). The power numbers won't be very accurate, but they will be precise enough to allow quality training like "ride at 90% of FTP" which is how you train via power. 

To correlate HR, just make a chart of what power corresponds with what HR. That should get you pretty close. Yes, there are variables that decouple HR from power especially on late-fatigue workout stages, but for the most part, it's pretty good. 

It's a good idea anyway to know how your body responds both in terms of HR and power for perceived effort on race day. More than once I've found one or the other unreliable on race day unexpectedly.

Thanks everyone for the replies!

I started my training based on HR then a couple of weeks ago started thinking about power. My wife stumbled across TrainerRoad and it looked promising; I could build custom workouts based on HR intervals on my plan. Then I find out that TR only uses virtual power for the custom plan creator. Bummer!

Still, power interests me and I'm pretty certain I'd get stronger with a PM. The downside: I don't have a dedicated PM and really not in my budget. So, even though TR is $10/month, once I'm on the road it's all a guessing game.

Thanks again everyone!

Fyi, it's not actually necessary to use power for 100% of your riding to see benefits from using it.

I train with virtual power on the trainer, most of my rides are on the trainer.  I monitor HR too while on the trainer but don't use it as a training metric.  In fact I cannot achieve the same LT HR average on the trainer as I can outside, its was always about 4-6 bpm less.  For the trainer, HR lag during any kind of interval workout makes HR undesirable for me, especially comparing the 1st interval to the last interval.  VP you know what you have to hit and maintain and is a vast improvement for monitoring gains. 

I monitor HR on outdoor rides and during races and correlated RPE.  This past spring I PR'd a sprint by sacrificing some speed on the bike and keeping HR in low-mid Z4 range and being able to blitz the run.

FYI, there's a new trainer program out in beta (maximum trainer) that allows you to build workouts in either HR or W.  Its free and getting good feedback/reviews.  The developer has been very response to fixes and improvements and I'm slowly adding the BT Winter Cycling Plan Power workouts to it.

You can start out without the $10/month investment by using veloreality or maximumtrainer. 

Just a quick update: I used Maximum Trainer last night for the first time. The "virtual" PM is all new to me but I can see how I can (more or less) correlate power with HR. This is just my first impression.

Everyone has been extremely helpful with your replies. Of course, now I'm looking at a couple of "training with power" books (Joe Friel and Hunter Alan).