Indoor Cyclists: Turn the fans off!

Somewhere (I think it was in a That Thriatlon Show podcast episode), a coach postulated that most of the relative “gainz” of indoor training were associated with heat adaptation. I agree.

I’m coming of a week of traveling where I had a trainer but no fan, no A/C. I was outdoor and temps were between 65-75 F, no wind and relative high humidity.

I only did 8h total of training, but I trained every day, with 3 hard sessions, one of them (threshold) was a real struggle to finish.

I never sweated so much in my life. I was very much on top of hydration: tablets, Pedyalite. Hydrated like never before. At the end of the week I felt like if I had done 15-20h of training:

  • Sort of tired but with motivation to keep training.
  • Low resting heart rate
  • Orthostatic Hypotension….possibly due to increased plasma volume?
  • Increased vascularity in the legs, very notable.

The sessions were: Recovery, vo2, threshold, SST and Endurance x2. All in all, the increased stress seemed to have helped a lot to turn a compromised traveling training week into a productive stimuli.

Highly Recommended!


P.S. I recognize that a lot of times the purpose of training is to hit your best watts, so perhaps for those key sessions, help yourself with more cooling, longer recovery periods, etc.


Funny how it’s all relative. That would be a cold day for me.


All this might be true but as long as:

  • I have more time to increase volume
  • can recover more high intensity training
  • can increase carb input

I will do all or some of those before playing with fan :slight_smile:

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So you did 8 hours of training but you felt like you did 15 to 20h hours. That doesn’t sound like a good deal to me.

*note: i do see the benefit of heat adaptation, but only if you need to perform in the heat.


Did you mean hypotension, that is feeling faint when standing up quickly?


Reminded me of this podcast: Unpopular Opinions on Group Rides, Riding Inside, and Hydration - Fast Talk Laboratories

If heat adaptation is a goal. I’m not sure heat adaptation is going to help me in my A events - Tour of Flanders Sportive, and a mid October Irish Gravel Race. Actually help me in any of my Irish races this year - maybe 1 or 2!

I thought that too, but TIL that both are possible, though hypo is more common.

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Fans? Indoor training for me right now is in the 30’s (F) in my garage - I’m concerned with not freezing my toes and nutz off if the intensities are low.

But, some good podcasts in the past, I think with Tim Podlogar (?) on heat adaptation. I think it’s a shorter term thing, so the advice was start ~4 weeks out from an event or whenever you’re going to need to perform in the heat. (Although there was some speculation I think around long term benefits - but I don’t remember it being definitive.)

For me, indoor training is for maximizing gains. As cold as possible, as much airflow as possible. Then as I get to summer, I’ll be doing 6-7 hour long rides in 85-90 (F) heat and humid to bring on the heat adaptation so I’m ready to go for an event in those conditions.


Might be thinking about this one…

Same. I haven’t used a fan for indoor training since the beginning of November. It’s just too cold. I’m usually wearing shoe covers as well.

They aren’t referring to heat adaptation and I think it would / could help you.
I been playing around with heat training for about a year and have noticed some fitness gains I would have struggled to achieve without the heat sessions. Its a bit like a poor mans altitude training.


This is timely for me. Just this week I started doing my TR endurance rides with no fan for heat acclimation. Anything with effort I’m still using a fan and making sure I do the work but for zones 1 and 2, I just let the sweat fly. I’m doing BWR CA end of April and live in MN so I thought it might be good to get some heat now because it could be hot there but will not be here by then. Basically an experiment on my part, I have not read the research on this.

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Whether it’s exposure to heat or cold I’m in . I’m not just race or ride focused . I try to blend overall strength, fitness ( aerobic -anaerobic ) , and riding . So if I can get a ride / trainer workout out in as well as a good sweat , i will . Of coarse it depends on room temperature but Typically anything over tempo and the fan goes on or I feel it is going to be counterproductive for me . Overheating should be avoided, there is a line , sweating is one thing, heat stroke is another. It should feel good not terrible.

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This is what GPT4 has to say:

“The physiology of orthostatic hypotension in endurance athletes is a complex interplay of cardiovascular adaptations that occur as a result of their extensive training. Here are the key factors:

  1. Increased Plasma Volume: Endurance training leads to an increase in plasma volume, which improves cardiovascular function and endurance. However, this adaptation alone doesn’t fully protect against the rapid changes in blood pressure that can occur with position changes.

  2. Lower Resting Heart Rate: Athletes often have a significantly lower resting heart rate due to increased vagal (parasympathetic) tone and greater cardiac efficiency. While this is generally beneficial, it can contribute to a slower response in increasing heart rate when standing up, delaying the compensation for the sudden drop in blood pressure.

  3. Enhanced Vasodilation: Endurance training enhances the capacity of blood vessels to dilate, improving blood flow during exercise. However, this vasodilation can persist at rest, meaning that upon standing, there can be more pronounced pooling of blood in the lower extremities.

  4. Venous Return: The increased capacity for vasodilation, combined with a lower resting heart rate, can affect venous return when an athlete stands up quickly. Gravity causes blood to pool in the legs, and if the heart and blood vessels don’t adjust quickly enough, it can lead to a temporary drop in blood pressure.

  5. Baroreceptor Sensitivity: Endurance training may alter baroreceptor sensitivity. These receptors help regulate blood pressure, but changes in their sensitivity can affect the body’s ability to quickly adjust blood pressure upon standing.

In summary, the physiology behind orthostatic hypotension in endurance athletes involves their lower resting heart rate, enhanced vasodilation, changes in baroreceptor sensitivity, and increased plasma volume. These factors, while advantageous during exercise, can paradoxically predispose athletes to a temporary drop in blood pressure and dizziness when they stand up quickly. This phenomenon underscores the body’s complex adaptations to endurance training and the delicate balance involved in cardiovascular regulation.”

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I invite anyone of you to come to ride in my garage in Florida in the middle of August. During the middle of the day with no fan, it’ll be great for those adaptations you’re looking for.

If you survive…


I’m in the exact same boat, but one step behind! I am just north of you in MB and am doing BWR CA, which means that I’ll struggle with heat again. In 2022 it was real bad, hitting mid-90s in the canyon, and it really wrecked me. I was considering turning down/off the fans as an experiment, especially for the endurance rides, and see if I get used to the heat at all. This thread has me (mostly) convinced to at least try it.


From your symptoms sounds like your suffering from a combination of heat exhaustion, dehydration and reduced plasma volume due to salt loss.

Personally I’m going to continue to use my fan in my mid 30s Fahrenheit garage so that heat stress is not impacting my ability to complete workouts. As the weather warms up I’ll get heat acclimatised naturally.


Yeah plasma expansion is triggered by heat stress. The orthostatic stuff you’re noticing may be sodium deficiency though. If it is, it will probably go away within an hour or two of eating about a tspn of table salt. It’s fairly common for amateur endurance athletes to run into issues with sodium deficiency when training in the heat, as daily requirements end up being much higher than normal (easily more than twice the normal DRI) due to sweat losses.

Heat stress can impair your ability to perform though. I would be cautious about deliberately avoiding cooling (if your goal isn’t heat adaptation) as heat stress might impair your ability to train hard enough to get the adaptations you want.

Ex: I don’t deal well with heat until I (reluctantly) adapt. This past summer I wasted almost a month of training by insisting to train outside even though it was really hot, and I could never consistently hit power targets. Eventually went back inside, was able to hit things consistently again, and broke through the plateau.