Pain Cave Temperature, HR and training benefit

I’m interested to hear some inputs on if/how temperature can affect HR, and in turn, if this can ultimately impact the desired training benefit?

When I train indoors, I have AC blowing and a large fan circulating the air, so the room in nicely cooled. By the end of each workout, I seldom have more than a few drops of sweat on the trainer mat. Certainly no pools of sweat.

OK let’s take an example of a VO2 max session. My legs are working in the desired power zone, but my HR isn’t reaching the corresponding HR zone. In fact, indoors I have never threatened my max HR.

I know I am working in the correct power zone because I performed my recent FTP tests in the same environment with the same trainer and same PM. My PM is also zeroed before each and every session.

In this scenario I’m guessing that said VO2 max workout isn’t having the same impact that it would if my HR was up where it should be, at least not from a cardio point of view?

Increasing the room temperature would undoubtedly help get my HR higher, but is it necessary?

Any inputs on this?

What about your cadence?

This doesn’t answer your question, but I live in Houston and even with the AC at 74, when it’s 90 degrees outside with 90% humidity, you just can’t overcome the heat when training. My heart rate soars and my ftp falls in summer. I always get excited about my gains in the winter only to see them regress come late spring.


In cold conditions, the body restricts blood flow to the torso, to preserve body heat for the vital organs. As the body’s core temperature rises, the body opens blood vessels to allow more blood to flow to the limbs, and closer to the surface of the skin, so that heat can more easily escape. At this point, the heart is not just an pump circulating oxygen-rich blood to muscles, but also a heat pump. In warm conditions, HR will be higher than the effort itself justifies.

The point of aerobic training is to improve your body’s ability to use oxygen. Getting your HR up through working out in warmer conditions won’t improve this. In fact, you are probably better off working out in cooler conditions and just imposing training stress on the body, rather than adding heat stress as well. Power is a better guide to your body’s oxygen consumption than heart rate.

(Of course, there is a strong argument for heat acclimatisation as you get closer to your target event, but that is a separate discussion).


My cadence is probably around where it should be. SS/TH I would normally spin around 90rpm. For Vo2 I’ll be up >100. Higher cadence does help lift the HR but not as much as it ‘needs to be’

This exactly, focus on power and keep training as you have been. As you near your “A” event consider heat adaptation if needed.

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I definitely notice a difference when it is warmer. All winter I was able to keep the thermostat at 60-61 with the option of opening the adjacent unheated garage door for extra cooling. I have an industrial fan on a table right in front of my front wheel and 1 on the floor/side. With this set up I sweat minimally, and have trained better than ever.

Now as warmer temps are creeping in my AC only goes down to 65 and the garage doesn’t offer any benefit. At 65-70 degrees I am finding work outs MUCH harder and lots of sweat. I shave my head and sweat alot from there so I can usually tell how hot I am when salty sweat gets in my eyes. During recoveries I try to work on my aero position which has a benefit of bringing me lower/closer to the fan which helps a ton. But I am struggling to think about further cooling options (new thermostat that allows for lower temps, 1/2 freezing bottles overnight, etc.).

Anyhow, my n=1 says that even 5-10 degrees makes a huge difference in effort required for the same workouts…

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In the interests of science I conducted a quick experiment today with Galena +3 (4*20mins SS @ 90%).

I started the session with no AC, only fan and my Garmin had the temperature around 28°C. My other thermometer had it around 30.5°C.

I did the warm up and 1st 20min interval without AC and the temperature naturally got higher. My HR for this SS interval was more in line with what I’d expect for a TH interval.

After this 1st interval, I kicked the AC on, so the room temperature dropped. Interval 2 my HR descended the whole time. Intervals 3 & 4, when the room was cooled down, my HR was probably more in line with what I’d expect to see for a 20min SS interval. Albeit a shade higher.

Without doubt, the room temperature had a significant impact on my HR, my RPE and also the amount of sweat on the floor :joy:


this is me exactly!!! im going to try adding a dehumidifier and industrial fan…if that doesnt work im gonna set my training to peak in june…its just too brutal for me to go hard in high dew points…those conditions seem to affect me more than most

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Yep. I’m wrapping up base phase right now, planning to peak in October when things cool down, but before Thanksgiving and Christmas, when I know I’ll be traveling or have guests in the house.

Just chiming in with my recent experience. I just finished ssb2 HV with my basement in the mid to upper 70s F and humidity in the 60-70% range. It was tough but I think my HR normalized after a few sessions. And I just finished recovery week and did all my endurance sessions outside with temps in the low 70s and humidity around 100% in recent mornings and have felt fantastic, HR was low for me in the 120s for workouts in the IF range of 0.6-0.7 so I think whatever I did in this block worked

My pain cave (corridor) tends to vary between 14 and 18 degrees (57-64degF) accordingtothe garmin. Before my major op last year I hardly sweated but that had something to do with the cancer. I’m stronger now in terms of watts per kg post cancer but I sweat buckets. Sweating buckets though seems to allow me to go sustainably longer #JustCallMeLance :smiley:

Just to toss out an interesting shot of anecdotal evidence…I decided to do a 3 week block all outside. Current forecast in Texas is for 102 today and 106 tomorrow. The first few rides outside in this were brutal. The last few I’ve done without really even paying attention to the heat.

After 3 weeks, I went back inside and did a workout. I completely smashed my record HR for that workout both in terms of low (7 beats under the average for that workout), average (6 beats lower) and maximum HR (7 beats lower) all at the same power I did prior to my 3 week heat block. I did the same workout a few days later inside, same result, everything HR related all much lower that anything I had seen in months.

Found it interesting and while I usually focus on power I was surprised to see my HR at specific wattages so much lower. I gained some efficiency from the heat work and it has translated to my heart needing to do less work for the same output while indoors.

I don’t have any conclusions other than that and I’m not making a recommendation or getting an invite to be on the Olympic Long Team because of it but hey, I thought it was interesting to see.


Here in NorCal this past weekend was 104 Saturday and 103 Sunday. Like you said the first few rides in June were brutal, but now I don’t think anything of it. As I understand it, one of the primary adaptations related to your decreased HR observation, is an increase in plasma volume:

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Do we know if an increase in plasma volume can also lead to or is also associated with an increase in FTP? Not something I’ve ever spent any time on. It would be an interesting virtuous cycle… indoor focus on power, outdoor focus on heat, which leads to an ability to do more power indoors…etc.

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it can bump your vo2max, and hence you might expect an increase in FTP. My best ramp test was after doing some 2-2.5 hour weekend rides in 100F heat. Then after it cooled off around Nov 1st experienced a minor ‘fitness crash’ (FTP dropped from 250 to 230) and was truly baffled until learning about adaptations from heat training.

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