Starting Position: Stand with your feet hip width apart. Depress and retract your scapulae (pull your shoulders down and back) without arching your low back, and "brace" (engage your abdominal/core muscles) to stiffen your spine.
Step forward by slowly lifting the right foot off the floor, stabilize your body on the left (stance / supporting) leg and avoid any sideways tilting or swaying in your upper body by maintaining the abdominal bracing. Keep the left (stance/supporting) foot pressed firmly into the ground, hold this position momentarily before stepping forward with the right foot. The right (swing) leg should initiate contact with a heel strike first, slowly transferring your body weight into the right (leading/forward) foot placed firmly on the floor. As you lower yourself into the right leg, maintain a straight spine by leaning forward from the hips and lower your right elbow on the inside of your right knee.
As you lower yourself into the lunge, focus more on dropping your hips towards the floor rather than driving your hips forward. This will help control the amount of forward movement of your shinbone (forward tibial translation) over your foot. Place both hands on the floor with the right slightly forward of the left and continue lowering your body to a comfortable position or until your front thigh becomes parallel with the floor and your tibia (shinbone) is in a slight forward lean. While in the lowered position with both hands on the floor, push back through the left foot to extend the left hip and maintain the abdominal bracing to keep the pelvis stable and increase the stretch to the left hip flexor.
From the lowered position, keep your abdominals braced and push your hands into the floor to begin to raise yourself back to a standing position. Press the right (forward) foot into the ground and drive the right knee backwards to create knee and hip extension and pull yourself forward into a standing position. Keep your chest lifted and abdominals braced to maintain a straight spine and level pelvis while beginning to swing the left leg forward to initiate the next repetition and stretch in to the right hip.
Continue the exercise for a specific number of repetitions or over a certain distance of travel.
Exercise Variation: to add a stretch for the hamstrings before stepping in to the next lunge, push off of the floor with your hands, lean back and push the right foot in to the ground to straighten the right leg while shifting your weight into your left hip and stretch the right hamstrings. Alternate with both legs.