i am currently training for my 40 yard dash time and i am also a solid 4.4 guy but i am trying to get into the 4.3's by the end of this summer. what i do for speed is, in this order, fast feet movements on stairs or flat ground for turnover, then i do a lot of plyos for explosion both single leg and two leg plyos, then i sprint with a sled 4x20 yards then 4x40 yards then i do overspeed with a bunji pulling me for 60 yards and i do that 2 times. from there i left weights, power or hang cleans, sinlge leg squats, lunges, deadlifts and RDL's....do this twice a week and i'm sure youll see huge improvements.