To increase power, strength and mobility, adding even a few minutes of plyometric training to your usual routine can add intensity to your workouts while building more power and strength in the legs.
As a form of body-weight exercise that requires minimal or even no equipment (other than your own body), plyometric movements have been around virtually forever, although they didn’t start out as “exercise.”
Getting your muscles to contract & expand efficiently is key to good power, you can't just rock up & expect to do a one rep max lift or squat if you've been out of the game for a while.
Increased rate of "force development" and neural drive of the muscle following resistance training
is what you want, so in the video doing "plyometric eccentric jumps" ( jumping down then up repeatedly) is a sure fire way stimulate the muscles & so improving exercises like squats.