# Relationship between Watts and HR



## kingfisher (Mar 6, 2009)

This season I'm trying to stick with a traditional Joe Friel approach to training, and have spent the last two months riding primarily base miles, ranging from 12 to 18 hours per week. I have one more base month before I start into "build" cycles.

I've been using 290 as my FTP, based on my initial estimation and then a 20 minute test a month ago, so my zone 2 is 160-200 watts. Most of my riding is in zone 2 and those miles are generally NP 190-200 watts. 

I've noticed my HR in zone 2 has gradually dropped from around 135-140 bpm to 120--125 bpm. In fact, my HR has dropped a comparable amount in zone 3 as well, and my resting HR is the lowest I have ever recorded (41). The RPE of riding in these zones has also dropped. A challenge now is keeping warm when riding in zone 2.

I'm pleased with the outcome, but I'm a bit perplexed. The power meter says I'm riding at the same level of intensity, but the other indicators of effort (HR and RPE) say that I'm not riding as hard. Further, how can my KJ output be the same when my HR is so much lower? 

Does the drop in HR indicate a need to adjust my zones? Honestly, I don't think riding at 125 bpm for next 3 weeks will produce much training benefit. I think I would lose conditioning by riding at the level, even if still pushing 200 watts.

Thoughts?


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## woodys737 (Dec 31, 2005)

Calibration issue maybe. At least that is the first thing I thought of.

Riding at a constant power for long periods of time always results in a HR that slowly increases for me. I don't ever recall HR dropping in this situation...probably messed you up more. Sorry mate!


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## Ghost234 (Jun 1, 2010)

That zone 2 seems a little low for that FTP. One of my earliest FTP tests had me at 265 and I still remember my zone 2 being about 160-200. 

But that aside, maybe your device needs to be zero'd, batteries changed, or the computer is the problem. I know that when the battery started to die on my Garmin the numbers would start to get a little wonky. I was absolutely shocked to see that I pushed 1450 watts (22.8 w/kg) on a sprint - when I know I physically cannot push that. 


My best advice would be to get the device zero'd, calibrated, etc. and train by heart rate until then. After a month or so of riding with power you should have a general sense of what your heart rate is when pushing a certain level of watts anwyays.


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## Undecided (Apr 2, 2007)

That says to me that you've become fitter over those two months and it's time to retest for your FTP. "Indicators of effort" are not the same as measurements of work. If you've ever read (here or elsewhere) that HR-based estimates of calories burned are unreliable, you'll have read explanations of the baselessness of HR as a proxy for energy expenditure.


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## kingfisher (Mar 6, 2009)

I just got the power meter back from Quarq (new antenna and calibration), but I should check it again.

To clarify, my HR does drift up over long rides, but is now much lower within the zone 2 wattage range.

If the power meter calibrates properly, I'll test FTP again. Ugh--an all-out 20 minutes is never fun.


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## DMH1721 (Aug 30, 2010)

Sounds like your body is adapting and becoming more efficient -- requiring less energy (lower HR/lower RPE) to produce the same amount of work (might be mixing metephores)


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## Daren (Jul 25, 2008)

Heart rate is a reactionary measure of effort that is effected by more factors that just power output. My heart rate is all over the place, from zone 1 to zone 4, when riding at the top end of my zone 2 power. It is most likely that you have adapted to the stress on your cardiovascular system over your training program. In addition, if your hear rate zones were calibrated using the Lactic Threshold Heart Rate test, or something similar, after a season end recovery period, that too would cause the hr zones to be a bit higher than they would be at the peak of your fitness.


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## sdeeer (Aug 12, 2008)

Definitely test again. It is most likely that your FTP has increased and you are now at a lower relative intensity while in zone 2. 

My FTP is estimated at 286 right now and I use Friel's basic method as well. My zone 2 rides tend to be a IF of .76 with a NP of about 220-235. I like to target the higher end of zone 2. I am not getting in 18 hours (most 11-15 depending on the phase), so that my TSS/week is managable. My HR falls from about 140-145 at the top of my zone 2 to 135 for the same watts as I go from base 1 to 2 and then to base 3. I adjust up my zones as appropriate for each new phase. I modified Friel's set up to do a 2 on and 1 "off" approach. I test every third week after 3-4 days of about 1-1.5h of mid range zone 2. (after some recovery and a tick up in TSB). I do the warm-up, 5 min all out, 10 ez, 20 all out method to estimate CP and FTP. They say testing is training. So basically 1 hard workout that week and one "long" ride with the rest relatively easy. 

If you use golden cheetah, it calculates aerobic decoupling which is an indicator (in a sense) of fitness. If you are riding in the lower range, then your heart rate will likely stay low as it is. If you re-test and then ride at the upper end of that new range (at least some of the time in your zone 2 base miles) you push more TSS and theoretically more training adaptation.


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## Alex_Simmons/RST (Jan 12, 2008)

kingfisher said:


> I'm pleased with the outcome, but I'm a bit perplexed. The power meter says I'm riding at the same level of intensity, but the other indicators of effort (HR and RPE) say that I'm not riding as hard. Further, how can my KJ output be the same when my HR is so much lower?
> 
> Does the drop in HR indicate a need to adjust my zones? Thoughts?


1. On your rides, how does it feel? If riding at given power level feels easier, it probably is. You will likely need to lift your power training levels to match your improving fitness.

2. Your HR is irrelevant with respect to efficiency (mechanical energy output as a proportion of total energy metabolised)

If you ride an hour at 200 watts, you will metabolise in kJ: 200W x 3600 seconds / GME* 

* GME - Gross Metabolic Efficiency, typically falls somewhere in the range 18-24%. Chronically it doesn't change much for an individual. Acutely it can vary with things like hydration level, temperature and so on.


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## kingfisher (Mar 6, 2009)

Thanks for all this feedback. I checked the calibration last night, and the power meter says its calibrated (Quarq). For my base 3, provisionally, I think I will ride at the top end of my zones, and test and adjust my zones at the end of base 3.


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