Zone 2 Outdoors. Prioritize heart rate or power?

On an outdoor Z2 ride, is it better to prioritize heart rate in Z2, over power in Z2, or vice versa?

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Heart rate, indoors and out. I try to keep mine just a few beats below the Z2/Z3 margin for a good Zone 2. Try to find a flat route with as little opportunities for obstructions/stoppages as possible. If you get to a hill wind it back to keep in the Zone. A few beats over for a few minutes won’t matter but any more and then walk it (as long as no-one is watching)!!

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For me the answer is ‘it depends’, but usually power.

On a longer (2+hr) endurance ride some degree of cardiac drift is to be expected when holding a constant power. If my HR is a little high for the last 30mins of a 4hr ride i’m going to stick with my power target.

In the later stages of a training block when you are likely carrying some fatigue (which often causes a suppressed HR) then training to HR could be causing you to push significantly too hard and risk overtraining/burnout.

The only time i’d ride to HR rather than power is if I saw that my HR was high from a very early stage in the ride - then i’d put it down to a bad day and reduce power to stay within HR zone.

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On my indoor trainer up to 3 hours (not done any longer) I don’t get any cardiac drift at all. My Zone 2 HR is 95 -117 bpm. For the first 10 mins or so of a zone two ride ( on a typical Systm app Zone 2 workout) seems to give me the highest heart rate possibly up to around 112-114 bpm then it settles down to around 104-106 and stays there but goes up to 108-111 if the power requirements for the workout goes up say 10 watts and then stays there until the power requirement drops back. I can generally on a good day keep in my Zone 2 range up to 160 watts which is for me 2.6 w/kg

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I would state that the Endurance rides set a power band for outside and warn about staying in the requested Zone 2 heart rate band. I suffer from a rising heart rate but usually after a particularly hard effort (like trying to get back on the group or a 250m 20% grade climb) and suddenly find myself in Zone 3 or even Zone 4. Getting back to Zone 2 takes time.

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I would stay within zone 2 power but ride to heart rate and RPE. With time and training you should see less cardiac drift and higher power for the same heart rate.

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I would stick to HR. The entire idea of Z2 training is to see the power go up while HR stays the same (at least that’s what I see). So just stick to a given HR and with enough (and I really mean enough, it takes months …) perseverance your power number will rise (slowly).

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Not to be controversial but I’d do RPE. The power “targets” were originally conceived not as targets at all, they were descriptive rather than prescriptive.

So, ride at whatever pace you can finish and still feel good. That’s an endurance ride. Whatever the power or HR is, it is.

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To add on, heart rate rising is not necessarily a bad thing. Means your smaller motor units are fatiguing, so you’re relying on bigger ones (Henneman size principle) which are by definition less efficient and need more oxygen to do the same work. But I’d that a problem?? Those motor units probably need the work!

@JayKay - if you have tested recently and your metrics are set correctly, start your ride at the low end of your zone 2 range. Likely your heart rate will start off in your zone 1 HR. It takes a little while for your heart rate to respond to the effort and over time it will creep up and eventually will come into your zone 2 HR. As long as your heart rate is in zone 2 you can ride in the middle of your zone 2 power range. Now if your heart rate begins to creep outside of zone 2, then I would recommend backing off the power. Power metrics are instantaneous, while heart rate response have latency or delayed response. This is why it is OK to start at the low end of your zone 2 power, while you wait for your heart rate to fully respond. After your heart rate stabilizes, then you can slightly increase or decrease your power, with your aim to keep your heart rate in zone 2.

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