Improving your Vertical

There are many different theories and ideas about how to improve your vertical.  Old myths seem to include slow deep heavy squats, along with heavy calf raises and lunges.  However, more recently I  have changed the way I have been approaching this.  I now do barbell jump squats with 50% or less of my 1 rep max instead of deep heavy squats.  I do 3 sets of 10 repetitions.  After a 6 week trial my vertical improved 3 inches. All the while, protecting my lower back from becoming overloaded.