Noticed if I enter a workout with a simple definition of - “MARATHON 42.2km 290w” - then intervals.icu populates a duration into the workout that is actually pretty close to what I forecast (notwithstanding might lose a bit of time due to undulations).
What is this duration based upon? Is it real and dependant on my data, or is it just a fluke that it seems to match up?
There is a relationship between W/kg and metres/sec. It will depend on what device you use to measure power as all are different. It depends on how effective you are in turning the power into forward speed.
Ie m/sec = RE * W/kg. (RE is variable representing Running Effectiveness)
My personal relationship for a flat course with no wind (Stryd wind pod) is m/sec = 0.98 * W/kg.
Thats good, but how does intervals.icu know that?!