I have no record on this. But I believe that my 3 or 4 star academy players could gain about 200% when they were still in low star. But their training efficiency should drop a lot when reaching scout level.

I just check my record in more detail and notice that a 20 years old highest 4 star GK gained average 142.7 (131, 164 & 133) through high intensity practice match before just he was sold.