Regarding AK and MMT Not me, too nonspecific typically. If you have a "weak" muscle, it could be the nerve root, an entrapment, or any one of the muscles that support or stabilize in that motion in addition to any of the passive restraints (capsule, labrum, ligaments) that might not be doing their job and causing the body to be "weak" when in reality the body is guarding that motion. For that matter a muscle could test weak because of a fracture or instability in the bone, or in AK land, also organic dysfunction, so how do you connect that dot with the legitimate dysfunction?
I used to use Kendall & McCreary's manual muscle testing fairly regularly, but in all honesty the time to information gained isn't completely beneficial. I use it occasionally if signs, sx and presentation don't correlate or I need an extra level of documentation.
Haven't delved into MAT too much yet, just have a knowledge of what they've provided on the site, so I can't really speak to that.