If you want to get faster than your friends, or faster at crits and closing gaps in races, listen to Zach Allison, and do this workout. It's gut-wrenching, but it'll give you guts too.
Benjamin Sharp talks Hill Repeats, and how because of the constant counter force of gravity, the inertia and torque requirements to climb are unique. When riding on the flats at the same power requirement, it’s very challenging to have the same intersect of force and cadence. If you don’t have hills to climb in your local terrain, riding directly into a headwind can mimic the nuances of trying to climb.