Originally Posted by
FBinNY
That said, "under load" isn't an absolute notion. Loads vary, and experienced riders can shift under load because they have developed good shift habits, and unknowingly (or intentionally) ease up at the critical moment to allow the shift to happen smoothly.
Or you just time the shift so it happens when your pedals are at 6 and 12 o'clock. There's very little load at that point in your pedal stroke.