The vastus medialis or VMO is the tear-drop shaped muscle on the inside of the knee. Unless specifically targeted in training, it commonly falls behind in strength compared to the well-developed lateral (outside) muscles.
This exercise will keep the VMO from lagging behind. It's something all athletes should be doing at some point during their workouts. Not doing so leaves them vulnerable to knee problems and future injury, like ACL tears.
You got the introduction to MRT last week, now here's the meat. If you've got limited time but want maximum results, this is your baby. The cool thing? The workouts won't take you much longer than 30 minutes.