The standing quad stretch focuses on the quadriceps (front-thigh muscles). Be extra gentle with this stretch if you're prone to knee or lower-back pain. If back pain is an issue for you, you can do a similar stretch while lying on your side, bending your top knee, and bringing your heel toward your buttocks.
Stand tall with your feet hip-width apart, pull your abdominals in, and relax your shoulders. Bend one leg, bringing your heel toward your glute, and grasp your foot with your hand. Hold for 20-30 seconds and then switch to the other leg.
Progression - Push hips forward for a deeper stretch in the quadriceps.
Regression - Perform stretch laying on front.