If you think of a stoppage at the half back line, when players spread from the contest, surge forward and gets on the end of it in the forward 50, they have sprinted for about 15 - 30secs.
Lactic Power is an all out sprint for time that exceeds Alactic Power which is 10secs.
Before you can faster at running from the back line to the forward line, then you must be able to do it fast in the first place as you cannot repeat speed that isn't there in the first place.
The LACTIC POWER training manual is a 3 week program that progressively builds on your alactic power.
By the end of the 3 weeks you should have increased your meters per second time over a longer distance then at the start of the program, indicating the ability to maintain high speed for longer.