These are two parts of discussions I had with none other than Mr. Sommer himself. Hopefully it will help you guys out there. Good luck!
...I was wondering if you could answer a question of mine. I've been trying to find the most efficient way to train my legs for the primary purpose of increasing my vertical leap. I've been doing pistols for a while, and can now do 3 sets of 5 (strength training parameters) fairly easily. I was wondering if you could suggest a better routine. I was also concerned about the effectiveness of pistols themselves for increasing vertical leap, as I was under the influence that glutes and hamstrings where more important when it came to jumping...
...Single leg squats will continue to work fine for you if you either a) progress onward to more difficult variations or b) simply add weight (weight vest, dumbbells, plates or sandbag on the shoulder) to the basic single leg squat.
More difficult single leg progressions could include:
1) single leg squat with jump
2) single leg squat with jump for distance
3) single leg squat with jump for height
a) jumping up onto a box
4) single leg squat for jump and distance
a) jumping up onto a box from a distance.
...The squat is only quad dominant when performed as a half or parallel squat. Performed as a full squat (butt to floor) there is significant engagement of the glutes and hamstrings. The issue for conditioning is not with the squat itself, but with people performing half range of motion (ROM) variations.
You are quite correct in asserting that the section of the body from the lower back down the glutes to the upper hamstrings is the primary mover for explosive movement in the lower body. I will share with you that in Building the Gymnastic Body there are some very hamstring/glute specific exercises which should make you quite happy (as you smile through the pain! )...