You are forgetting about the efficiency of the human body. Roughly, only 21% of your power is transferred to the bike. So a professional adding 400W to the bike is actually consuming ~1900W of power. This all matches up with their nutrition [1]. Namely

> They averaged 91 g of carbs every hour across all of the stages.

That's nearly 400 calories worth of sugar simply while riding the bike. In fact, I would say cycling is a clear counterproof of this article. Their equations are literally (calories in)*efficiency = power and they know exactly how much to feed. I don't disagree that 99% of people are better served eating less, but doing cardio for 2 hours a day + diet management will lead to very quick weight loss. "Very quick" here is 2lbs/week but people have some insane expectations.

[1] - https://www.welovecycling.com/wide/2021/07/01/how-much-do-th...

If you are pro-athlete, I think you could, but 1kW is probably about max a human can burn for longer periods. I managed to output 500W for 5 minutes of rowing, but I'm overweight couch potato.

I think you need to account for human inefficiency. I have to burn more than 1 joule to output 1 joule on a bike. The average efficiency of a human on a bike is somewhere around 20 to 25%.

Cycling is only approximately 25% mechanically efficient, so the parent is correct. There's a lot of heat to get rid of.

Apparently 700kcal burned per hour of cycling is a pretty realistic number.

https://www.welovecycling.com/wide/2020/05/14/how-to-convert...

Also resting kcal burn might be around 1800 per day. So 40% increase in of calories burned by hour of cycling per day every day is achievable.

The question is how can you breathe out additional ~10h of CO2 within an hour?

3 times deeper breathes 3 times faster? Because that carbon has to go somewhere.

The CO2 concentration going up in the blood increases the efficiency of respiration (because it is ultimately diffusion).

You don't necessarily need to exchange 10 times the volume of air to deal with the additional CO2.

Range given for concentration of CO2 on exhaled air is 4-5%

So it looks like it could be 25% difference at most.

I doubt the 4-5% you saw is a first principle of breathing.

Why not? CO2 levels in blood must be tightly controlled. It probably can't get twice as high as usual.

If there's already 4% of CO2 in the air around you it's an immediate danger. While you can spend 10 minutes in 3%. If your body could bump up CO2 in exhaled air from 4% to 8% then you'd probably have bo problem surviving in air thay contains 4%.

Its a mix of anerobic and erobic exercis. Its hard to keep the same heart rate while biking. So sometimes the body doesnt need oxygen to burn fuel. So it doesnt exhale co2. As said I am no expert.

https://en.m.wikipedia.org/wiki/Anaerobic_exercise

That might be it. Thank you. If anyone wants to read more about it it's called Cori Cycle and it doesn't require oxygen and it doesn't produce CO2.

But you'll need to get energy eventually from normal beathing to recycle lactic acid back into glucose in the liver.

So probably after an hour of intense exercise you'll be breathing out more CO2 in the following hours as your body clears up lactic acid.

What's interesting is you get 2ATP from making lactate, but you need 6ATP to recycle lactate back into glucose.

Would that mean that for burning more calories you should have as much of anerobic excercises as possible because it's really ineficient use of glucose?

Thanks for the hint. I didnt know that one needs co2 to get rid of lactact

And to that question as said I am nonexpert. Imho sport after a certain (1h or so) time is a mix of both and should burn most calories in a healthy way. As far as I know there was a downside to having too much lactat. And burning calories aint synonym with burning body fat. Short intensity anerobic training is not atacking bodyfat in my opinion. It only uses the reserv in carbs we have anyway ( around 2000kcal) Biking is the best exercise for bodyfatburning in my opinion. If it is more than 2h.