The vast majority (24/28) of the participants were football players, which suggests that they were accustomed to speed training and the 40 yard dash The quarter squat group was already the fastest group to begin with. They went from 4.68 to about 4.58 on average, which is quite decent. Their vertical jump increased from 75 to about 86cm. the full squat group didn’t improve their sprint performance at all. Seems highly unlikely that in higher trained athletes this trend would be significantly different, although the magnitude of improvement would probably be reduced. A lot of world class track and field athletes use the quarter squat, which is now supported by scientific research.
This makes a lot of sense because joint angles in sprinting and jumping exercises are a lot more smilar to the quarter squat. Using the quarter squat allows you to use heavier loads in the relevant joint angle ranges. When using a full squat, the load is not challenging anymore once you get into these joint angle ranges. The study shows that strength increases are quite specific to the type of squat used, so the full squat does not really improve strength in the joint angle range used for sprinting and jumping.