After addressing some serious weaknesses the past two days, I'd like to review one point of progress I've made this year. I have become better at using the "bounce" in the bottom of a squat. I'd read about the hamstring stretch-reflex which can help propel an athlete out of the bottom of a full-depth squat, but hadn't been able to feel it until this Autumn.
I think it took me a long time to develop the back strength and hamstring flexibility necessary to use the bounce. Until recently I had a "butt wink," or loss of lumbar curve, in the bottom of my squat. My hamstrings were pulling my back into flexion. Essentially my tight hamstrings and soft back were absorbing the bounce.
Here is a video of my overhead squat this March. Look for the quick rounding of my back in the bottom of each squat. Also, note that my heels come off the ground in the bottom of each squat - another sign of tight hamstrings.
Next is a video of my squats two days ago. Watch me start up fast, due to the stretch-reflex, then grind up slowly through the middle.
Now, if I can just keep my knees all the way out to the sides....