Comment by scotty79
3 years ago
> If I bike for an hour I burn 700-1000kcal . Thats not 15 but 50% of the dayli calorie intake…
That's estimated and probably impossible.
1000 kcal is 4184000 joules, divided by 3600 it gives you around 1100W
Human at rest burns about 100W. Pro-cyclist can do additional 400W. There's no way you can burn energy at the rate of 1.1kW consistently for an hour unless you literally set yourself on fire.
EDIT:
I was wrong.
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.
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.
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