I know when I trained we used doses between 0.5 w/cm2 and 1.5 W/cm2, pulsed and unpulsed. We used it for mechanical effects or at the higher doses fore heating effects. But whatever we were told to always keep the head moving.

Current practice suggests we were being way too zealous and I gather that the whole idea of using US for heating is now frowned upon. the potential damage that standing waves cause on cells is well documented in the lab.

I remember even we were shocked when in a neurology placement the therapists were using US to reduce spasticity. The theory was to bombard the golgi tendon organs with mechanical energy, that would inhibit the overactivity of the muscle. So the idea was to hold the head stationary on 3 w/cm2 continuous on the tendon. Dreadful idea and think what damage we could have done. Anecdotally it did seem to reduced the stiffness of the muscle, at least temporarily.