The semimembranosus is one of the three muscles that make up the hamstring group, running along the back of the thigh. Located on the inner, or medial, side of the back of the leg, it is often stretched along with its neighbors, the semitendinosus and the biceps femoris. Targeting the semimembranosus requires subtle adjustments to maximize the stretch on this specific muscle fiber group. This guide provides instructions for safely and effectively stretching the semimembranosus muscle to improve flexibility and reduce tightness.
Anatomy and Function
The semimembranosus muscle is positioned deep within the posterior thigh, lying beneath the semitendinosus muscle. It originates at the ischial tuberosity, the sit bone at the bottom of the pelvis. The muscle fibers extend downward to insert on the posterior aspect of the medial condyle of the tibia.
Because it crosses both the hip and knee joints, the semimembranosus performs two primary actions. It is an extensor of the hip, moving the thigh backward, and a flexor of the knee, bending the lower leg. When the knee is bent, this muscle assists in the medial, or internal, rotation of the lower leg. Tightness can restrict the full range of motion at both the hip and the knee.
Essential Safety and Preparation
Before attempting any static stretch, engage in a light warm-up activity, such as a five-minute walk or light cycling. Warming the muscle tissue increases blood flow and pliability, preparing the fibers for lengthening. Stretching a cold muscle can increase the risk of strain or minor tearing.
Maintaining proper pelvic alignment is important when stretching the hamstrings. If the lower back rounds, tension is distributed into the spine instead of isolating the intended muscle. Focus on hinging forward from the hips, maintaining a flat back. This ensures the stretch originates at the ischial tuberosity, where the semimembranosus begins.
A stretch should feel like a deep pull or tension, but never cause sharp or shooting pain. If pain is felt, the stretch is being pushed too far or the technique is incorrect, and the position should be immediately eased. Remember to breathe slowly and consistently throughout the hold time, as holding the breath can increase muscle tension.
Step-by-Step Stretching Methods
The key to isolating the semimembranosus muscle is to incorporate a slight internal rotation of the leg, which aligns the stretch specifically along the medial hamstring complex. This is achieved using two distinct methods: the Seated Straight-Leg Stretch and the Supine Hamstring Stretch. Both stretches should be held for approximately 30 seconds and repeated two to three times on each leg.
Seated Straight-Leg Stretch
The Seated Straight-Leg Stretch is performed while sitting on the floor with one leg extended straight out and the other leg bent, with the sole of the foot resting against the inner thigh. To specifically target the semimembranosus, slightly turn the toes of the extended foot inward toward the midline of the body; this promotes internal rotation. Hinge forward slowly from the hips, keeping the back straight, and reach toward the ankle. Continue until a deep pull is felt along the inner, back portion of the thigh.
Supine Hamstring Stretch
The Supine Hamstring Stretch uses a strap or towel to control tension while lying on the back, providing support for the pelvis. Begin by lying on your back with one knee bent and the foot flat on the floor. Loop a strap around the sole of the foot of the leg you wish to stretch, then gently pull on the strap to lift and extend the leg toward the ceiling until a stretch is felt.
To specifically emphasize the semimembranosus, gently guide the raised leg across the midline of the body. Slightly rotate the foot inward so the toes point toward the opposite shoulder. This diagonal positioning and internal rotation directs the lengthening force toward the medial hamstring fibers. Maintain a neutral spine throughout the movement, ensuring the back remains flat on the floor.