You gotta do it until you bawl, then the other leg. Try some at 50 cadence, same gear as legs together or maybe 1 cog smaller, and some at 80-85 cadence, tiny gear. The more intervals you do, the easier they get until you get exhausted. It takes a couple intervals before my legs start working properly. Open those blood vessels, get nutrients on site, etc. Keep a tight chain, that's the main thing. I guarantee results. Cheaper than buying Powercranks.