Used by physical therapists, athletic coaches, movement specialists, etc. Muscle testing is used to detect weak or inhibited muscles that may be causing physical problems – pain, weakness, balance problems, etc. For example you have pain in your knee when you squat. Someone trained in muscle testing, could use muscle testing to isolate and test the various muscles of your upper leg and may find that one or several muscles are not contracting properly causing your leg to go out of alignment when you squat leading to pain. They may prescribe special exercises to strengthen and get those muscles working properly which would then eliminate the pain.