Arr. Yes the concepts of PNF and Muscle Energy. Different mechanisms are at play also depending on whether you are resisting a force or pressing again a force. So this also has an effect. I would have thought a grade 4- would be more appropriate to use this as a technique rather than a grade 3, which is afterall on muscle testing a strength that permits joint movement but not against gravity. Or are you discussing a different muscle grading for force rather than strength?