This may be relevant, or not. All the discussion of lig. Fatigue and connective tissue adaptation reminded me of something I experienced years ago. I was assistant instructor at a traditional Japanese Karate dojo.
When students first started training they tended to lack the ability to create the kind of power karate requires. As their training continued their power grew, along with their speed. After about a year of hard training they were getting to where they could throw good, hard techniques. And frequently, that would be when they would pull muscle, or strain a joint.
It seems that the ligs and tendons grow stronger at a much slower rate than muscle. I don’t know if this will correlate to PE training, but it might be something to consider.
I’m enjoying this forum, and appreciate the amount of generosity and knowledge available here. Thanks.