well u still dont completely lose your hops. For ex., if I bench 300 lbs now, and stop benching for the summer, i'll "lose" my bench and drop to about 225. However, I can quickly raise it back up to 300 in a couple of weeks. So it's more of a temporary loss

Also, I did some research and the reason ppl are getting hurt is because they are gettign jumper's knee.
http://www.hughston.com/hha/a_13_4_4.htm
two things causes this, one is overusing the knees (which air alert does) and the other is if you're going through a growth spurt, you're more likely to get jumper's knee. And I'm pretty confident that 50% of this forum is under 15 and the other 50% used this program when they WERE under 15, which is why everybodys getting hurt.