Mine was that I and a partner deliberately wanted to see how long we could last and the relationship of volume/performance/time. Basically I ran a loading phase where I made very small jumps but kept volume very high and constant. In the final weeks the workouts were monumental efforts just to get the work done on every set. We were pretty toasted by week 5 and at week 8 we were falling asleep standing up, unable to concetrate, just walking zombies. Had to quit at that point. That's full overtraining vs. overreaching, hormonal profile in the shitter and cortisol through the roof I'd imagine. That took about 4 weeks to recover from enough to even have a decent feel good workout. I think for somewhere between 2-3 weeks we didn't even lift - really hurting and not functioning well, living in a slow cloudy head so to speak. When we got back in the gym it took a while to get back to where we could make enough progress to get our lifts back to where they were before this all started. So basically we chucked a multi-month block and a significant portion of a year. I've always been an experimenter and while this definitely added to my understanding and ability to manage fatigue and feel various levels all the way out it was exceptionally wasteful.