Pay attention to Justin's directions. Play the exercise slowly...very slowly at first. Concentrate on technique; hand and thumb position, curled fingers, pressing near the fret and sounding the notes well. And, perhaps most importantly for the purpose of increasing stretch/flexibility, keep the fingers in position as Justin directs. When you can do all that, then increase the speed.
Take heart. Justin talks about his 'stubby' little finger and how he can't take the exercise down past the third fret. Me too. Third fret, sometimes second fret, is my limit but some day I'll make that six-fret stretch from the first position. :D
Christopher S. has some great off-guitar warmup exercises posted in Lessons ( https://www.guitartricks.com/tutorial.php?input=1525 ). These are important and also can help stretch and flexibility.
My practice is pre-planned but what is practiced changes from time to time. One of the longest lived segments of my practice plan was the exercise above followed by chord practice. My stretch/reach/flexibility really improved...I'm sure it will work for you too.
"It takes a lot of devotion and work, or maybe I should say play, because if you love it, that's what it amounts to. I haven't found any shortcuts, and I've been looking for a long time."
-- Chet Atkins
-- Chet Atkins
