tamfb, he’s talking about the acceleration phase of the fly…how much acceleration, over what distance, before he actually enters what would be considered the max speed 40m.
To answer him, I would say that it depends on how long it takes the individual to reach >90% of Max V. Probably at least 30m, and maybe 40m or more for faster athletes. The acceleration doesn’t have to be full tilt, and can even be done off the slope of the indoor track to conserve energy prior to entering the Max V phase on the flat and straight portion of the track.