The most common quadriceps stretch is actually the most effective for our needs. Standing next to a pole or wall for balance, raise the first leg behind the body, grabbing your foot. The upper part of the leg remains in a vertical position as you pull the leg upward. See Figure A.
To completely stretch all quadriceps muscles, try the following variation. After completing the stretch shown in Figure A, pull your leg back as in Figure B.
In both variations, be careful not to pull your leg laterally; this puts unneeded stress on the knee.
Observe Figure C. The leg being stretched is parallel to Jack’s support leg. In contrast, Figure D shows the leg being stretched pulled to the left.