One of my friend was excellent sprinter with PB over 200m 21.22. However, he hit the plateau for a couple of years. He wanted to quit and he wated to move to bobsleig. He did a lot of strenght work and he improved his strength a lot with gain bodyweight around 10lb. He did only short speed work 20-30m and sometimes longer run. Afrer that he was very surprised with his competition times (still wanted to compete occasionally)over 200m he improved to 20.71! and mainly with weight and acceleration work.