In order to improve speed, an athlete must do 3 things:
Apply more mass specific force into the ground
In the proper bio-mechanical positions
In ever decreasing increments of time
Apply more mass specific force: its important to remember that the ground is a force plate. What you put in, you get back out. When an athlete sprints, the more force he can put into the ground (that’s mass specific), the faster he will sprint
Mass specific is the key because when an athlete sprints, they have to overcome their own bodyweight. This is why for example a sumo wrestler can be very strong, but a terrible sprinter: their strength isn’t “mass specific” meaning their relative strength, their pound for pound strength, is poor.
On the other end of the spectrum, a thin weak athlete also doesn’t sprint fast because while their bodyweight is low, they also lack relative strength. They fail to produce enough force into the ground in order to sprint fast
This is why its said, “Fat doesn’t fly but neither does weak”
What most athletes are missing in order to get fast is raising their relative strength. Once they get pound for pound strong, they find huge improvements in their speed.
So in order to apply more mass specific force, an athlete must get stronger, WHILE improving their body composition.