Front Lunge Begin with a front lunge stretch — back leg straight, front leg bent. Your knee should be stacked on top of the heel and tracking over the toes. Straighten and lengthen the front leg in a slow controlled pace, stretching the hip flexors while strengthening glutes and hamstring muscles. Modification: Start with both legs bent, then both legs straighten at the same time. Perform for 8 slow reps. Repeat on the other side.