Doing the right exercises can be pretty confusing. In fact, you can walk into any gym and see dozens of leg machines being used with many different variations.
Many professional bodybuilders say, to some extent it is necessary.
In fact, most believe that by varying the foot position and knee position with some exercises, you ll be able to selectively target specific areas of your leg. However, the existing research done in this area by exercise scientists suggests that these variations may not only be a waste of time, but may also subject the joints to unnecessary risk of injury. These EMG studies measure the electrical activity produced when the muscles in the legs contract during exercise. The higher the electrical energy, the more work the actual muscle is producing. They also reported that medial rotation or turning the feet inward produced the highest level of electrical activity in the outer sweep of the quadriceps.