Originally Posted by
hamster
It's not hard to demonstrate that it isn't.
Let's use a calculator at
Bicycle Speed (Velocity) And Power Calculator and plug in some numbers. For simplicity, assume that we have a trip that consists of 1 mile uphill at 4%, 1 mile downhill at 4% and 1 mile flat. Pick "racing bicycle - hands on the tops", plug in bike weight 20 lbs, rider weight 160 lbs, power 145 W (2 W/kg - very conservative for a male rider getting back into shape), leave all else at default values.
Hmmm.
My own personal power data from a couple 200Ks, a 12 hr race, and a bazzillion training rides suggests that my ultramarathon limit is at around 60% of FTP. And that's if I am highly motivated. More realistically, it's closer to 50%. That ultramarathon limit is reached somewhere around 6 to 8 hours, or longer.
For a 160 lb rider, who is essentially new to the sport, to have an FTP of 280W is pretty unrealistic.