This is a simple and very useful trick, tapping sprint gives you better distance and combined with Ruthless Perk it allows for infinite sprint if done correctly.
The timing is roughly in pace with the footsteps of the character, press and hold while you can hear each footstep and release slightly before the thud ends.
This trick with Ruthless Perk is also useful for getting away from Thorax Swarms that otherwise eat all of your sprint.