This is an excerpt from Running Science by Owen Anderson.
Six-Way Lunge With Arm Drop
This exercise strengthens and stretches the hamstrings and gluteal muscles in all three key planes of motion: sagittal, frontal, and transverse. Strong, flexible hamstrings and glutes stabilize the knee during stance, control the leg during forward swing, and help provide the propulsive force needed for powerful strides.
Stand with feet pointing straight ahead, hip-width apart. Bend the arms at the elbows, with hands in front of the shoulders. Step forward with one foot into a long-lunge position (figure 13.13a). As the forward foot makes contact with the ground, drop the hands on either side of the forward knee. Quickly extend that knee to bring the hamstrings and gluteal muscles into action to return the leg and body to the original, standing position. Repeat this exercise on the other leg.
To continue from the standing position, step directly to one side into a lateral-lunge position (figure 13.13b). The upper body should face that side and lean forward over the lateral-lunge leg at about a 30-degree angle. Drop the hands on either side of the lunging knee as that foot makes contact with the ground; keep the other foot pointed straight ahead. Extend the lunging knee to activate the gluteal muscles and hamstrings and bring the lunging leg and the body back to beginning position. Repeat the action on the other leg.
Then, from the original standing position, step diagonally and to the rear with one leg into a backward lateral-lunge position (figure 13.13c). The upper body should face to the rear and lean over the backward lateral-lunge leg at about a 30-degree angle from vertical. Drop the hands alongside the lunging knee as that foot makes ground contact; keep the other foot pointing straight ahead. Extend the lunging knee to activate the hamstring and gluteal muscles to help bring the body back to the starting point. Repeat the pattern using the other leg for the prescribed number of times.