I was so proud to get this picture. Only because I have never seen Dave do a lunge. I remember many, many years ago (this must have been in 1998 or so) I read a training log that Dave had posted and he referenced lunges in it. Don't ask me where I read it or where it is now. Doing so would akin to asking me where the hell my virginity is; that's been lost for many, many years. Whatever... So I figured lunges were part of his program.
Now in my many years being at EFS and knowing Dave, I had NEVER seen him do a lunge before. In fact, I've never seen him lunge accidentally. For example, let's say you drop something and it falls under a table. Many people would perform a lunge-like movement to retrieve said item. Not Dave. It would either be left there or he would fall to his knees and pick it up.
Having said that, the exercise is pretty simple. Put a weight vest on and lunge. Do it for some reps and a few sets - you know the drill.