Please help me with the basic principles behind power output

Could someone please help me understand the principles behind power output? I had a decent time in school back in the days but also often found myself dreaming I were somewhere else, especially during the physics lessons…:wink:

Imagine this (simplified) scenario (IRL or in a virtual trainer situation):
I’m riding alongside a friend up a 7 percent climb. I’m 193 cm and 80 kg, he is 165 and 62 kg and we are both using the same brand and model of power meter, calibrated of course. Let’s say that the display on our respective cycling computer is showing a constant 240 Watts (just an example, don’t know if it’s a reasonable output in this scenario) – does this this mean that we are going up this hill at the same speed and will reach the top at the same time?


Your friend will charge ahead of you all else being equal in both the real world and in Zwift.

Aero drag is typically a factor up to ~8% gradients, but power to weight ratio is king… You would be doing 3W/kg while your friend is doing 3.8W/kg in your example.

Oldie but goodie calculator for seeing how weight and Watts affects things…


Thank you Steve. The silly thing is that when reading your explanation it all seems so obvious.