Originally Posted by
Will Morris
A couple of things that jump out immediately:
1) You are not getting set prior to the repetition. There is no change in your back, as I see no deliberate effort to set your lower back with an isometric extension movement. You are definitely not performing a proper Valsalva, as I should be able to hear you take in a large breath. Performing a "karate hi-ya" is not the same thing. I think this most certainly leads into #2
2) Your knees are all over the place here. They slam back too early in the first rep or two, and by the third rep, you are letting both knees collapse in and you almost do a bit of the Australian river dance coming out of the hole. This is going to be cured by making a deliberate effort to keep your knees out after the rebound. Actively push your knees out going down and hold them out coming up until about half way up. Tendon and myotendinous junction does not like rotational components and your femurs going into internal rotation secondary to loss of active abduction and external rotation is going to be problematic.
3) If you clean those up, then just modify your sets and reps and perform shorter sets and increase the total number of sets. In-set fatigue is public enemy number 1 with musculoskeletal injuries in the gym. Reduce your reps to 2 reps, and perform 7 sets with as heavy a load as you feel comfortable doing. Increase this weight each session until your doubles get close to what your original working weight was. Then, start adding reps per set until you are back to your regularly scheduled program.