You’ve described rehabbing and acute tendonitis. Chronic tendonopathies of multiple years here need way more loading that isometrics to start. That’s a waste of time as these athletes are training through the injury. OverLoading the contractile unit is important to improve tendon strength and to help realign fibers. However stretching of the tendon (repeated stretches lasting no more than a couple of seconds in sets) is extremely important. There will be pain, but this should resolve within 10 minutes. There is no other way a tendon can return to its premorbid length without consistent and frequent stretching. These stretches must be repeated 5-10 sets per day. Since it takes at least 3 months to create a true chronic tendonopathy one would expect at least two-three months of consistent stretching and progressive overloading of the tendon to return to full pain free strength. As with most injuries, if you sit on it all day and the train aggressively it won’t get better. Some level of relative rest is required.
Andrew you are not aligned with the evidence for treating tendinopathies.
It is absolutely fine to start with isometrics.
It is contraindicated to stretch the tendon because: It does not ‘lengthen’ from stretching, it’s a very low tendon load and you are just causing compressive loading. Remember that for a tendon to remodel, we want fibroblasts to differentiate into tenocytes. They do this from tensile loading. By stretching you are inducing more compressive than tensile loading, causing fibroblasts to differentiate into chrondrocytes.
And you can not realign disorganized collagen: since it’s disorganized no load will go through these fibers and they will have no signal to adapt to.
I think you should read Tom Gooms article about high hamstring tendinopathy and listen to Pete Malliaras podcasts.
I would also like to add: there is no evidence to support that ‘X is weak, you need a comprehensive scan’ or whatever when you have high hamstring tendinopathy. It’s a local problem and can be rehabbed back to 100% by just treating the tendinopathic tendon. Since you gonna need to do some weights you might as well get overall strong, but it’s very unlikely that someone athletic have “glutes that wont fire” (you would not be able to climb stairs), “unstable core” (you would lose your balance) or any other biomechanic boogeyman.
If you have this injury: Read my post here and remember: you are capable and strong even though you have a painful tendon. You dont need to believe that something is deeply wrong with your glutes, core, or whichever ‘flavour of the month’-disability that therapists want to sell to you.
In this thread MKen has the evidence based answers.