Consciously contracting quadriceps for 5-15 seconds can be used to understand muscle spindle and spinal cord circuit mechanisms.

“So, what I'd like you to do is if you're in a proper place to do this, you're going to stand with legs straight, meaning knees not bent, and you're going to try and touch your toes, or for some of you that's going to be very easy and you might even be able to put your hands flat on the floor. [...] Okay, now what I'd like you to do is stand back up and I'd like you to contract your quadriceps as hard as you possibly can for about 5-15 seconds. Let's say 10 seconds just to keep things more or less normalized.”