Note that these are very generous estimates, but it does demonstrate how silly the idea of trying to generate electricity by capturing exercise output is (in a purely economic sense).
It's a lot more than that. Even a fit (healthy, but not necessarily peak athletic shape) adult man will have about 15% body fat, 20% for a woman.
I heard pro cyclists can reach up to 2kW. I managed to make 500W on a rowing machine for 5 minutes, but I'm a couch potato. I believe 400W is a normal rate for cyclists. When you are sitting, your body already produces about 100W of heat.
This hugely depends on body weight / gender / training levels etc., body weight being a big deal since that’s what you’re transporting. So the other way folks measure output is W/kg of body weight.
A beginner adult male will be in the 100-200W zone, around 0.5-1.5 W/Kg. Usually anyone can train themselves into the 200-300 (3-4 W/Kg) zone which is the recreational pace - the groups of cyclists you see on the road. Beyond 300 ftp (150lb body weight) (4-5 W/kg) you’re reaching race pace. The ones you see on screen have upwards of 5-6 W/Kg FTP output. They obviously have other constraints around putting this output at the end of a 200km ride for 20 mins etc as well, which makes it extra hard.
Finally we come to the KW numbers - all these folks have two kinds of muscles (fast twitch and slow twitch). The sprinters are saddled with a higher proportion of the kind of fibers that can allow huge spurts of power - they put out about 1000-1500W for about 5-10s. These are probably what you’re thinking of. This is pretty much an end of ride (or a sprint section) empty your tanks effort.
Semi related tidbit: track cyclists are a middle kind of beasts here: they put 600-1000W for a couple of minutes but don’t have to worry about riding 200kms to get there.
On the other hand, it is possible to imagine lifestyles enhanced by various 10W contributions. 10W for heated clothing. 10W for a laptop. 10W average to power a several km electric bicycle or Aptera-size commute. And so on.
Based on Ali Express, heated clothing (5V power in a pocket) is popular enough in China.
Not saying it's a good defense though.
