Bunch of people who don't understand heat transfer....or even simple definitions of convection, conduction, evaporation, and radiation.

This would make sense - the return to racing seemed to have an unusually high number of racers with "back issues"

I don't know, I think we have a better than average representation of engineers and physicists and aerodynamicists around here!

Yeah I just came back in March from a knee and hip surgery within 6 months. My power was doing good inside but once I went back outside a whole bunch of other stuff started to get sore.

Add in you’re more tense when biking hard. The back problems don’t really surprise me. You’re also just getting jarred on your bike for hours that by itself is exhausting and using muscles you don’t use inside

Nah, I take nothing on faith, and I have a history of disagreeing with real-world HVAC engineers, sorry. For some reason my most fundamental disagreements tend to be with the guys who tell me how expert they are ;)

As noted by an earlier poster, heat transfer in this situation is not primarily via simple convection but rather evaporative cooling facilitated by forced ventilation. Your psychrometric charts will show you where the energy goes.

What's "CFM" and a "2 ton" AC?[/quote]I presume these are archaic measures of power or volume flow rate or something?

What I was trying to bring up is how much heat these guys generate cruising and at intensity. Even though it may be possible to remove all that heat from their training environment, these pros cyclist may just not have enough cooling mechanism because they are not invested in a proper winter training set up like we are. They just generate a ton more heat per kilo to get to their optimal fitness and they have less surface area to remove heat from their overheated core because they are much smaller than larger age groupers. They will just run more "hot", affecting how hard they can go.

The ambient conditions are not an issue, however the boundary layer adjacent to the skin is.

Because you do not have the sun radiating down on you, there is likely a larger net flux of radiant energy away from the body. Convective transfer is about the same as outside (Depending). However, Evaporative cooling is likely greatly diminished and, unfortunately, is the most important to cooling in warm to hot conditions.

In still air, the evaporation from the skin will raise the humidity of the air around the body, which decreases the rate of evaporation from the skin as the vapor pressures become less diverse.

Now, with a fan we can mitigate this to an extent but never to the extent that we get for cooling when riding outside. This is why I do my testing in an environmental windtunnel. (for reference: https://www.instagram.com/p/BQliI3Ulrdu/).

The natural response is "Well yes, that's why I use a large fan or multiple fans" and I will say "Yes, that will help, but even a slight decrease in cooling eventually results in a substantial decrease in performance. This is because the issue is not the ability to produce watts, it's producing watts for a length of time.

This is where heat becomes an issue; it creeps up over time and eventually becomes a limiter to performance. So, yes, 1000w of heat production isn't a problem for 1 second, 1 minute, 5 minutes, but go 30 minutes and it makes a difference, go an hour and you're subconsciously dialing back the workload to protect yourself. 2 hours of hard effort? Almost impossible to reach the same workloads as outside.

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I talk a lot - Give it a listen: http://www.fasttalklabs.com/category/fast-talk
I also give Training Advice via http://www.ForeverEndurance.com

The above poster has eschewed traditional employment and is currently undertaking the ill-conceived task of launching his own hardgoods company. Statements are not made on behalf of nor reflective of anything in any manner... unless they're good, then they count.
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I'm not trying to argue that trainer use is a sufficient or desirable replacement for going out and riding as preparation for professionals riding Grand Tours. I'm just arguing that over-heating while riding indoors does not seem to me, the insurmountable problem you suggest.
Yes, a larger rider has more surface area, although this does not rise in proportion to their mass. A lean athlete will have much more surface area in proportion to their mass than a larger beefier rider. It's still less in total but then they will also be less well insulated (less subcutaneous fat) which I'd expect improves heat transfer to the skins surface at least a little. At the end of the day, more heat produced requires more cooling for a stable temperature and a smaller guy producing similar power may need more ventilation to achieve the required heat transfer. But since we know they can do this out on the road, and we know it's possible to achieve something comparable indoors, that should only be a limitation if the team doesn't pay any attention to it. It's solvable, without exorbitant expense. The cost of early season training camps which I presume were cancelled, would surely be enough to easily fund a few equipment upgrades?

Look how bad Thomas was off his indoor season at Dauphine and with more outdoor miles how strong he was a month later at Tirreno Adriatico. I am not sure when he got on his outdoor "season restart" but it may be a factor relative to the Colombians and Slovenians who have been outdoors the entire time.

For all of the time and money we spend on gadgets, I'm awfully surprised we don't see more examples of air conditioning units in the same space as trainers (and treadmills). The exhaust routing is pretty ugly, but it really completes the package after a fan and dedicated dehumidifier.

The coolest part of that post is the Kestrel Heat Stress meter. I need a wrist mounted Ant+ version for my 920XT---living and training in Texas.

Sorry, hadn't seen this before my last post.
So my point is that the investment required is not terribly significant. A few pretty basic fans and an open window is probably sufficient in cooler climates, and the existing AC will supplement this in warmer regions. I use an open window and two basic 450mm (18") fans that cost about €35 each if I remember correctly. I know a bunch of guys who train with a single tiny desk fan, or no fan, overheat on the trainer but don't think that's the problem - what can you do!

A few hundred € / $ / £ per athlete should be enough to resolve this issue and that shouldn't be beyond the means of the Grand Tour teams.

I've spent a solid amount of time riding with it strapped to my handlebars...

---

I talk a lot - Give it a listen: http://www.fasttalklabs.com/category/fast-talk
I also give Training Advice via http://www.ForeverEndurance.com

The above poster has eschewed traditional employment and is currently undertaking the ill-conceived task of launching his own hardgoods company. Statements are not made on behalf of nor reflective of anything in any manner... unless they're good, then they count.
http://www.AGNCYINNOVATION.com

Welcome to US HVAC engineering units. Don't forget BTU, and R-factor. Makes my head hurt trying to calculate the heat transfer characteristics of my house to predict seasonal energy usage.

Almost forgot KWh.

I presume these are archaic measures of power or volume flow rate or something?[/quote]

CFM is Cubic Feet per Minute
2 ton is 24000 BTU/hr or about 7 KW

I'll give it a miss thanks.

It's honestly unbelievable that even many technical professions in the US won't adopt metric. It's just so offensively backwards!
Although, to be fair, I have heard BTU used this side of the Atlantic too, but only very occasionally mostly in relation to domestic heating systems. I blame the US for this too - It's probably plumbers reading US product catalogues.
Only metric is used in reputable fields of engineering ;)

 
These goofy units do keep your unit analysis chops in order.

R-value is my favorite:

degree Fahrenheit square-foot hour per British thermal unit

Yay, I guessed right! I did think CFM was probably cubic feet per minute, but never heard of "ton" except as a unit of force (or is it mass?).

I'm okay with kWh. Just don't forget the "k" is lower case!

Running at noon around here....er, black?

Oh that's just horrible!
I'll take U-Value: W/m²K

I feel like I've hijacked this thread to bitch about US use of imperial units. I'll try and desist.

Tons of refrigeration:

defined as the rate of heat transfer that results in the freezing or melting of 1 ton (2,000 lb) of ice at 32 °F in 24 hours.

https://en.wikipedia.org/...Ton_of_refrigeration

I think Robert kinda nailed it. The Kestrel meter kinda takes any guesswork out of it. If you really want to know how the environment is affecting you, get the meter. Data not guesswork.

1 ton is the amount of heat required to melt 1 ton of ice at 32°F in 24 hours

I have refrigeration HVAC experience as well, not in homes but in automotive product development, air handling and chamber enclosures.

All Dev' s assumptions are reasonable and he makes a sensible back of the envelope calculation. Poses a very worthwhile question.

If fans can't allow the same evaporative cooling as outside then this is a very relevant concern for pros.