Train to power or heart rate

I have been using trainer road for just over a year and have gradually managed to increase my FTP. During this time I have been mostly been doing the sustained power building programs or prepping for a specific event.

I am currently nearing the end of one of these building blocks.

Previously I have done all the workouts at home on my wahoo kickr smart trainer. I am currently working away from home but have access to a concept 2 bike which I connect to trainer road via the app.

The problem is the gym I am going to is very hot and there is no fan available during my workout. My heart rate is going through the roof and I am struggling to stay within the prescribed heart rate zone whilst maintaining the desired power. This has not usually been a problem before when completely the 2 hour endurance rides set by training road and I can only assume it is because of the heat.

My question is, is it better to try and maintain the required power and have my heart rate shoot up or just forgot about the power and only train to heart rate?

Ultimately, the purpose of my training is to increase my endurance so I would assume zone 2 heart rate would be more beneficial. This would mean maintaining I much lower power, so would this be detrimental to my training?

Many thanks for any advice.

More of a unspoken consideration than an answer:

  • Keep in mind that the power reported between your Kickr and the Concept bike might be similar… but just as likely could be well apart. Perhaps you know this and have a gut feel for any delta per your experience on both, but worth a mention since we see assumptions that Power = Power when it is certainly not guaranteed.

Good point. However it “feels” similar between the two. My heart rate just keeps increasing and I end up sweating like crazy mid way through the workout.

My 2p (2c if you are any where other than the UK) Generally, if you have power I’d ignore HR for anything Z3-5 but for Z1/2 rides that are supposed to be recovery rides be mindful of HR and maybe ignore power. But for VO2 max stuff ignore both and pus to the maximum RPE. For the gym work though you probably need to rebase your FTP, different environment and different measuring device.

Yes if they’re recovery rides or if it starts to impact ability to recover appropriately before the next HIIT workout. If they’re more ‘endurance’ than ‘recovery’ though, then might it be advantageous to hold the power target as long as you feel like it’s close enough to the right RPE?

For example, maybe do Wednesday on HR so you’re fresh enough for a Thursday interval session, but do a 2h Sunday z2 on power and just bring some extra towels and maybe a spare bottle with ice water to cool yourself? Potentially even take a 5 minute break at the 1hr mark to cool down - not ideal but probably still better training signal than dropping power 10% over the whole session…

I put question marks because that’s my instinct and potentially how I’d proceed, but I’ve no experience of this kind of thing.

This sounds like a sensible approach. This week has been mostly focused on endurance rides and it is just a bit disheartening to get to the end of a so called recovery ride and be absolutely cooked.

I will dial back the intensity to 90-95% and see if I can hang on to the power.

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If you know your power, then at best heart rate is redundant, but at worst it is misleading.


Is there any chance you could talk to the manager of the gym and see is they can add some fans

Tonight I did a 1 hour Endurance ride based on power. Upper end of Zone 2. TrainerRoad labeled it Productive. My heart rate was Zone 1 until the final minute it finally crept into Zone 2. Was this still a worthwhile use of my time?

Talk to a few of the staff, there maybe be fans where they do spin classes or something and make an allowance for you

That’s a strange question - why wouldn’t it have been?


You are doing heat training whether you’re intending to or not. So, just stick to the lower end of your power zone and make sure to have plenty of electrolytes as you’ll be sweating more than normal. Some frozen drinks may help a bit and possibly look into a battery fan.


It certainly looks looks like that. Is there any benefit to heating training if I am not actually going to be cycling in the heat? I am just a bit concerned about not being able to hit the power numbers required and losing the training benefit prescribed by trainer road.

The gym is based in Angola and is nice enough but not really set up for this type of training. Or certainly not set up for having someone from the frozen North do this type of training! They have the AC running but it is still significantly hotter than I am used to.

“Reply hazy, try again.”

(Note that this is unlike the situation with training in hypoxia/at elevation, which only seems to benefit endurance performance under those conditions.)

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TrainerRoad’s Endurance zone is based off a fixed % range of FTP. Go see all the debates about Zone 2 in this forum to understand that your Aerobic Threshold may not align perfectly with the top of this range.

HR zones should be loosely related to their equivalent power zones. But, they are a lagging metric, affected by other factors on a day-to-day basis (hydration, caffeine, fatigue, sleep, stress etc). It also depends how you benchmarked your HR zones - e.g. from Anaerobic Threshold HR, Max actual HR, Max theoretical HR calculators such as 220-age, HR Reserve - all of which have a set of assumptions. So HR is an imperfect proxy for the equivalent power or indeed of internal strain.

As to whether any particular endurance ride is worthwhile - it’s all worthwhile until it drives you into a fatigue hole. Is it optimal? Perhaps you could make it more intense - push closer to your aerobic threshold. Or just add more time/add more rides. Either approach is potentially valid. Some combination will be optimal for your time and physical constraints.

Is the recovery ride you’re talking about the Black workout you did yesterday?

If so, that may have something to do with it :slight_smile:

On Recovery Weeks we normally only recommend Endurance workouts below a 2 Workout Level. This is to keep things intentionally eeeeasy so your body can recover for the next block of training.

Yesterday’s prescribed workout was Svinecea (Endurance 1.1) which is a Recovery type workout. I am guessing you manually picked Black (Endurance 4.3) which is a Productive type workout; so naturally you’ll be hitting higher target power which will in turn bring your HR up, not to mention external factors like not having a fan don’t help. :sweat_smile:

A good rule of thumb to remember is that if the workout is meant to be a recovery ride, then you should not be struggling with it. It should feel easy and meant to spin the legs out, not tackle in more training stress.


Thank you. I will look into this a little more when I have time. I may have my max heart rate set too high which could be skewing my HR Zones, but the ride did feel very easy.

I just thought that because my heart rate never left Zone 1, maybe it wasn’t really and “Endurance” workout

Which HR zone (level :smiley:) system are you using? Coggan’s?

(I ask, because I did only monitored HR for my “training” for a long time, using Friel’s % of LTHR zone numbers) and when I started getting into power I ended up having to shift to Coggan’s estimated/recommended HR levels for my power levels to (mostly) jive with HR, particularly at issue was the zone 1 and zone 2 HR break point)