Zone 2 and heat

Heart rate increases with heat… Keeping in zone 2 is a fair bit harder when it’s hot - presumably if you’re out of zone on a hot day, you’re still out of zone?

Are you training zones?

Yup, trying to keep my heart rate under 142

Simple. Use power.


Hmm, I’m mostly training leg muscles. And organizing training so I consistently do it. Maybe I’m doing it wrong.

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I find that over time I adjust every summer and hr stays a little lower. Having said that, I freeze my insulated water bottles and try to leave at civil twilight to keep the heat as low as possible. That does mean I’m usually in bed by 9pm on weekends though.


Very hard as nothing is flat here… It’s all rolling hills.

Early makes a difference for sure…

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Again I think it helps to think about what you are training and why. Yesterday I did a hot and slow 3.75 hour ride, kept it easy because I didn’t want extra recovery from the heat to impact tomorrow’s hard workout.

Technically I was out of zone for large portions of the ride, but I’m not training my zones. Over the years I’ve done a lot of easy top of zone1 rides in the dry heat, and I appear to get both a stimulus for heat adaptations and training.

Yes HR will be higher if the heart has to increase blood flow for evaporative cooling.


I think in general you are better to keep power for intensity (Z3,4,5 etc) and HR for Z1/2. I think its been discussed a few times on this forum. A quick search brought up Zone 1 & 2 rides by HR


Haven’t listened to this yet:

FWIW my coach works for FasCat.


I listened. Not a bad pod, but it’s not really anything new if you’re familiar with FasCat. TLDR is “we give you workouts with zones and we also tell you to get outside and ride”.


Interesting idea… To enjoy the outside rides more. I quite like zone 2 at the moment, work has been OTT busy so great not to have killer recoveries. But when things quieten down I will want to get back to faster club rides.


“Go ride your bike” from another coaching company:

knock power down a little if its hot and you aren’t heat adapted. Add time or late accelerations to close the gap on load:


62% IF instead of 70% IF? 144TSS instead of 172 TSS? Good enough and I’m at -2 TSS for the week so I preserved my weekly ramp rate.

If you live in a pass/fail world that probably freaks you out. I went to a college that graded on a curve. Grade yourself on a curve is my motto.


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On very hot days, especially if heat is combined with high humidity, your heart rate can be very high. I remember one time I was doing very low Z2 to upper Z1 and my heart rate was in the 150s. Granted, this was after a race and I was getting back from the venue (75 km one way).

The question is: what do you want to train. With Z2/endurance rides, one primary aim is to make your cardiovascular system more efficient. Your heart rate measures the load of your cardiovascular system. So yes, I would stick to heart rate targets to keep the load on your body low and avoid accumulating unnecessary fatigue.

If it is that hot/hot and humid, I would also avoid doing hard intervals or so outdoors in the middle of the day. Do them early in the morning when temperatures are more bearable. Or in the late evening if you prefer. Or do them indoors.

And make sure you have enough cold liquid with you. You could put one bottle in the freezer and fill the other with ice. (Just make sure to not overfill the bottle, ice is less dense than water.)

Are you racing? Or just building fitness for enjoyment?

If you’re racing, and your races require heat adaptations…then train your body to adjust.

Otherwise, wake up early, go late, train next to an air conditioner, ect. I wouldn’t lower your power outside, id lower your duration and progress from there. Or just know that heat is an added stress to your training and plan your rest/recovery accordingly.

I’ve had the pain cave temperature rise 3 to 5 degrees. I’m an INFERNO!!

The problem balancing the heat of riding and the cool of the A/C is real… :man_shrugging:

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Even here I would caution: training is all about balancing intensity and volume with recovery. Heat puts extra strain on your body. Yes, you can get acclimatized, but it will still put additional strain on your body and result in you not being able to dig as deep. Use with caution and use that deliberately.

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Not trying to be contrarian, however heat adaptations let me go deeper and put out more power. Repeatedly and reliably, season after season. It’s not always 96F / 36C every time I ride. Embrace the dry heat if you have it, and see if the same works for you like it does for so many out here.


Heat adaptations come naturally if you regularly ride outdoors in the summer, and it is hot or hot and humid where you live.

To get adapted during Z2 rides, pacing by heart rate (e. g. sticking to <= 140 bpm) has the advantage that it puts a comparable load on you and you will get quicker with time. If you always pick the same route, you should be able to see that comparing your times. But make sure to give your body time to adapt.

The other key word you used, dry heat, is important. Dry heat tends to be much easier on me. Cooling is alright in the dry heat if you drink enough. But in Japan, heat is usually humid, and humidity can play a number on you. E. g. when you climb, you are moving more slowly through the air and cooling gets worse. I remember having to pack a second pair of socks to change into mid-ride. In the South it was so bad that even walking had me drenched in sweat in no time, and I had to wait until sundown to go running.

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