Stiffness of joints

When doing sprints and plyos, should a person consciously be thinking about having as little give in the knees and ankles as possible?

When I coach plyos I have the athlete think of a cue that will result in stiffness as a byproduct. For example a cue for hurdle hops would be “quick as possible off the ground”, by emphasizing this the stiffness will occur as needed.

This is me doing some sprints, as well as other stuff for my workout the other day. Do you mind commenting and giving critiques?