ohh 3 weeks of inactivity thats a long time for a grade 1 hamstring tear you should have been ok to do static quads holding from 3 to 5 seconds to 10 seconds as a progression progressing to a straight leg raise being careful not to flex knee more than 90 degrees in first 3 weeks post repair weight bearing and loading the leg transfering weight onto operated leg all in time as leg strengthens also remember to keep incision site mobile once healed stop adhessions around scar tissue.