Thanks for sharing that info. I assume you are talking about 2 foot hops-using both feet. Is there any added value to doing single foot line hops or is this taking functional training too far?
I have done them, and do some other different things on one leg. With many kids who have knee pain from growing and lack of stretching the thigh, hip and ankle, they stay on both legs. Single leg hops are usually instant inflammation.
I use the hops in large groups as well, easy to do, little teaching involved, competitive.
Stay away from single leg stuff- asking for trouble.
Why not using single leg line jumps to find out if there is some difference btw left and right leg and thus a posibility for injury? Some of the performance tests to evalute readiness of ACL rehabilitated athletes uses the difference btw single leg jumps…
Without openining a ‘can of warms’ I have used single leg plyos using the same progression as ESTI (i think outlined here) with NO problems! But the volume was damn low: 3 jumps per leg for 1-2 sets and 2-3 exercises.
We did easy LLRRLLRR low hops but I never classified them as single leg stuff really. The farther you go, the more distorted your position is likely to be, the more the overload, and the more problems you run into.
A rugby player, training under my system, became the best player of his kind in the world- winning the “Golden Boot Award”
He went for an NFL tryout and the NFL team sent him to a well known single leg proponant for testing.
This guy (known to many on this forum) had him hopping down the hard track single leg, holding a Med ball for 100m repeats. He ruptured the guy’s achilles tendon in one day!
This was hardly his first or his last Achilles rupture, yet on he goes with the single leg shit.
Caveat Emptor!
You are being too much exclusive Charlie (and I guess I got this same characteristic from you – others tell me 
). Why NO-NO? It is a matter of a degree… 100m is a DUMB too much…
SL jumps test are used with much less volume/distance/number of jumps
- SL broad jump
- SL standing tripple jump
- SL jump over 6m on time
- Zig-Zag SL jumps
I guess it’s a matter of degree. you can do it till you need glasses. (ask your English friends for a more specific translation!)
I guess I understand the meaning
We gotta agree that we don’t agree… but hey I am beggining coach, and maybe some day I come to the same conclusions as you… 
Programming for single leg differences is not easy. I have used tests to determine differences and have been successful in some athletes to decrease the difference and not as successful in others. The mechanism for one person isn’t always the same in others.
No doubt single leg training can be dangerous as there is a fine line, as Charlie was trying to get across.
I just adopted the philosophy: “Total paranoia is total awareness!”
Since, what CAN go wrong usually DOES go wrong sooner or later, I figure if I don’t need to go there, I won’t.
Very true, especially with middle school and HS kids. They find a way to deviate = injury.