HR to Power zone matching

1

Hi,

I need help understanding the link between training zones based on FTP vs HR. I did Trainerroad Ramp test, result was 273W and my highest HR ever recorded was 191bpm (I did not do a max hearth rate specific test, it is just highest recorded during one of the most intense exercises). If I check the Intervals.icu “Settings” section, 7 training zones based on FTP do not match at all to HR. During last training target power was 60% of FTP (164W), which falls right in between Z2 power, but if I was training with HR, target HR would be 142 - 157bpm, when in reality during exercise it was 117bpm.

I’m 34 years, 75kg, 183cm it it’s relevant.

2

Are you asking if HR Zones and Power Zones should match?

AFAIK, It shouldn’t, as there’s HR decoupling at play, dehydration, perhaps a stressful day or something else.

You can also look at your Power/Hr efficiency… for you, at 164w you’re at 117bpm == 164/117 = 1.4 which, to me is really good. I’m struggling at 0.7++

3

But to which zone should you train than? If I wish to spend 2 hours in Z2 by power, my hearth rate will be far below in Z1. If I train in Z2 by HR, my power will be well above in Z3.

4

I would borrow @Gerald’s answer I’ve seen many times “it depends”…

It depends on what the session goals are. One of the thread you might want to take a look at is this.

5

If you have both Power and HR, always use Power as a reference. Power is an external load number and W/Kg is a solid number to define someones fitness and compare between different athletes. If you tell your coach that you can produce 4W/kg, he immediately knows that you are a well-trained cyclist.

HR zones are very dependable on

  • the Zone system you have set in the settings
  • max HR
  • LTHR
  • HRrest
    *State of fatigue, hydration, temperature…

And HR itself is always lagging. A Z7 Power sprint of less then 10 sec will barely be visible in your HR trace. Small bump in to the next zone…
If you tell someone you have a HRmax of 191, that is telling nothing about your fitness.

This doesn’t mean that you can’t train by HR zones. It just means that you will be able to tweak HR zones to be similar to Power zones.

6

@Rookie It’s important to know your Threshold Heart Rate (THR). Simply put, this is generally your average HR during a race that is longer than 20 minutes (the longer the better). It’s better known as your Lactate Threshold Heart Rate. It’s an intensity that we settle into during a race. It’s a point where if we go harder than this we’ll be forced to slow down and recover a bit. So, once you know your THR, go to Settings, Heart Rate Settings, and input your “Threshold HR”, input your your “Max HR” of 191, for “HRRc Min HR” you can put in a value of your THR minus 2 beats. Then click on Heart Rate Training Zones, click on PRESETS, select Andy Coggan. Now your HR zones will be a bit closer.

Keep in mind that a Ramp Test is not a true FTP test. It’s basically measuring your maximum aerobic power (i.e., your best 1 minute power, which can be a proxy for your power at VO2max), then it multiplies that by 0.75, giving you a pretty bad estimate of your FTP. Athletes with a high anaerobic work capacity can ‘cheat’ this ramp test pretty easily because they are making a lot of the power anaerobically as opposed to aerobically. Athletes that do long endurance work (think Ironman athletes), tend to score very low on ramp tests. Honestly, you would be better off looking at your power duration curve on Strava and looking at your power at 35 minutes, that will be a ‘truer’ estimate of your FTP. Then go to that ride where you had your best 35 minutes and look at your average HR for that 35 minutes and use that as your THR.

7

@Rookie Many will fight me on using the 35 minute mark of your Power Curve as an estimate of FTP. So I would challenge you or anyone to find that 35 minute power, then do a workout where you warm up normally then ride at that 35 minute power for at least 35 minutes AND for as long as you can.

If you can’t do it, then your FTP is lower than that number. If you can do a bit longer than 35 minutes, great, that is likely a good estimate.

Keep in mind that FTP is an intensity that we can sustain for about 30 to 70 minutes (depending on athlete type and goals).

8

You train in both, but watch the HR response (during and after) as well as the RPE & Feel scores (after) to calibrate the workout. Was it easier or harder than you thought? Were you feeling strong, normal or weak?

Training with power is in a range, which is why ERG mode is not ideal for training. Outside, one doesn’t use a controlled power source, so try not using it (at least with some sessions). If you feel good, try push a few % (of FTP) higher; perhaps the upper part of the range, and if you’re feeling weaker, ease off a bit and work the lower part of the range. In Zwift, they have the BIAS option, which can be manually turned up/down based on how you feel. It’s never absolute, which is what ERG mode tends to do. Then make notes in comments after the workout, so you know how to learn from that for the next time.

Heart Rate is the response to the work you’re doing, and you should know (or your coach should tell you) before you do the workout to compare the previous data of a similar workout. If HR was 85% of maxHR for the workout, and you now see 93%, for the same effort, there is something wrong. It could be up or down compared to average.

The wrong could be one, or more, of any number of factors:
Heat, fatigue, life stresses, illness, fear of failure, anxiety, etc.

Anything below LT1 is better to use Heart Rate, and see what power was produced. Use the HR cap to ensure you stay below the level, not at it. The reason it’s not done at the cap, is because you will get cardiovascular drift over time (fatigue sets in the longer the workout). Also, going up a hill will push the HR up and freewheeling/coasting will result in the HR dropping. The average HR and normalized power is used for the metric Efficiency Factor (EF = NP / Ave HR). Variability Index (VI = NP / AP) is also a good metric to pair with these easy rides, as it’s measuring “how steady” the workout is.

9

There’s one more difference between power and HR intensity dosing. When activity is below the anaerobic threshold (AnT), HR stays more or less stable for given power/velocity (excluding the above-mentioned slow effects like decoupling). But as soon as you go above the threshold, HR keep growing and growing until fatigue. HR also lags behind the exercise intensity (say, 30sec). As a result, HR cannot be reliably used for dosing intensity above the threshold.

That is why there are typically 1-2 HR zones above AnT while there might be 3-5 power zones. Those zones can be dedicated to specific training modalities like VO2max or sprint training. Corresponding HR will just be hard to predict for each workout