Role of Hamstrings in Walking

Walkers depend on strong leg muscles for speed and endurance. The hamstring muscles are made up of three muscles -- semimembranosus, semitendinosus and biceps femoris -- located in the back of your thigh. These large muscles play an important role in the different phases of walking.

Hamstring Anatomy

The hamstring muscles are three separate muscles that come together and form a common tendon, connected to your ischial tuberosity -- or "butt bone." As this tendon moves down the back of your thigh, it splits into three muscle bellies. The semimembranosus and semitendinosus muscles run along the inside of your thigh, crossing your knee joint and attaching to the bone on the inside of your lower leg. The biceps femoris muscle runs along the outside of your thigh, crossing your knee and attaching to the bone on the inside of your lower leg.

Hamstring Action

The hamstring muscles move two joints in your legs. As a group, your hamstring muscles move your hip backward, into extension, and bend your knee, into flexion. The semimembranosus and semitendinosus muscles assist with internal rotation -- rotation of your thigh in toward your body. The biceps femoris muscle assists with external rotation: rotation of your thigh away from your body. These muscles also stabilize your pelvis when you are in a standing position.

Stance Phase

Stance phase describes the phase of walking when your foot is planted on the ground. "Loading" is the beginning of stance phase; as your heel hits the ground, your body weight shifts onto that side. "Midstance" occurs next, as your foot flattens on the ground, leading to "terminal stance" -- your heel is lifting off the ground, preparing to move forward. Throughout the stance phase of walking, your hamstrings act on your hip joint. These muscles help stabilize your pelvis and propel your body forward by extending your hip backward. Electromyography studies have shown that hamstring activity during stance phase increases as walking speed increases.

Swing Phase

The swing phase of walking occurs when your foot leaves the ground and swings forward out in front of you. During swing phase, your hamstrings act on your knee joint. These muscles flex your knee, lifting it up away from the ground to prevent you from tripping over your toes. Hamstring activity during swing phase also increases as you walk faster.