Source? In cycling those numbers are elite level if not beyond. Numbers for rowing are hard to come by but lower[1], probably drag lowering efficiency (bicycle drivetrains are 90+% efficient).
To put it into perspective, 250Wh translates to 800~900 calories burned in a half hour[2]. That's not something most people around me can do.
During a bicycle race, an elite cyclist can produce close to 400 watts of mechanical power over an hour and in short bursts over double that—1000 to 1100 watts; modern racing bicycles have greater than 95% mechanical efficiency. An adult of good fitness is more likely to average between 50 and 150 watts for an hour of vigorous exercise.[clarification needed] Over an 8-hour work shift, an average, healthy, well-fed and motivated manual laborer may sustain an output of around 75 watts of power.
I guesstimate my 100k cycle place to be about 80w so that tracks. At the end I'm about ready to devour anything and everything that's put in front of me.
"The Gossamer Albatross is a human-powered aircraft built by American aeronautical engineer Dr Paul B MacCready's company AeroVironment. On June 12, 1979, it completed a successful crossing of the English Channel to win the second Kremer prize worth £100,000 (equivalent to £538,000 in 2021)"
...
"In still air, the required power was on the order of 300 W (0.40 hp), though even mild turbulence made this figure rise rapidly"
To put it into perspective, 250Wh translates to 800~900 calories burned in a half hour[2]. That's not something most people around me can do.
[1] https://rowinglevel.com/rowing-times/10000m-times
250Wh = 900kJ = 215 kcal at 100% efficiency; humans are ~25% efficient at turning food into mechanical work so ~860 with error bars