One of the benefits of many forward bending Yoga poses is expanding and stretching of the hamstring muscles. Therefore, it is ideal to take time in our Yoga classes to align the sit bones and leg bones so we can target the proper line of stretch of the hamstring muscles. With this alignment, we should understand the basic anatomy and mechanics of the various hamstring muscles. The hamstrings (posterior thigh muscles) consist of 3 long muscles that start underneath the gluteus maximus on the pelvic bone (ischial tuberosity), extend down the back of your thigh bone, cross over the back of the knee and insert along either side of your knee on your lower leg or shin bones. The biceps femoris muscle (long and short head, hence “bi”-ceps), runs down the lateral or outer side of the thigh bone. The other two hamstring muscles, semitendinosus and semimembranosus, run down the medial or inner side of the thigh bone.
By having key attachment points at the sit bone (ischial tuberosity) and below the knee, they are involved in the following:
*Semitendinosus and semimembranosus extend the hip (move the thigh bone posteriorly or ‘back’) when the upper body and torso are fixed, or they extend the trunk when the hip is fixed.
*Semitendinosus and semimembranosus flex (bend) the knee and medially (inwardly) rotate the lower leg when the knee is bent.
*The long head of the biceps femoris also extends the hip.
*Both short and long heads of biceps femoris flex the knee and laterally (outwardly) rotate the lower leg when the knee is bent.
*Hamstrings help to structurally stabilize your knee.
*Hamstrings assist the quadriceps and gluteal muscles in many leg activities.
By knowing where the hamstrings run and how they act on the body, we can manipulate the alignment of our forward bends to more effectively target the different hamstring lines. Most people have greater flexibility in the biceps femoris (lateral side) than the semitendinosus and semimembranosus (medial side). This becomes evident in poses like Janu Sirsasana (1 Leg Forward Bend) as many people find the thigh, leg, and ankle often turning outwards as they bend forward. As the body stretches into the hamstrings, the body expands into a place of less resistance. We want to maintain balance in the hamstrings, though, and expand the inner hamstring lines as effective as the outer lines. Therefore, before starting our forward bends, we should take a moment to situate the pelvis so the hip points create a perpendicular line to the forward leg (squaring the hips). This lines up the sit bone so that the all of the muscle insertions are receiving more equal expansion (not just the lateral edge). From there, we line the foot and ankle so the toes face vertically rather than allowing the thigh and shin to rotate outwards. This correction of the foot and ankle allows us to target the entire line of the inner hamstrings right into the insertion below the knee.
Other tips to consider:
*When folding in forward bends, encourage your spine, waist, and shoulders to be evenly drawing forward on both sides. If your torso curves over the thigh, you are most likely falling into the outer hamstring stretch and neglecting the inner hamstrings.
*Spread the gluteal muscles away from the sit bones in seated forward bends to allow a greater connection to the sit bones, thus adding awareness to the muscle origin.
*Enter forward bends, that involve the hamstrings, slowly. Stop part way into the fold so you can gently adjust and correct your alignment with ease. Entering stretches too quickly can cause stretch receptors to fire leading to muscle resistance, and often a reduced ability to fine tune your alignment. Find your attachment points and lines of resistance. Collect into your alignment and move forward with breath.
*Appreciate how the hamstrings create a ‘kinetic chain’ since they cross multiple joint structures. If the hamstrings generate resistance at one point in the chain, how is this resistance effecting the rest of the chain? Example: if you extend your legs (straighten your knees) in a forward bend, will this cause tension to travel up to the sit bones so much that it highly restricts movement at the hips, thus causing rounding of the lower back AND potential vertebral disc compression?
*Enjoy a slow exit. Prior to fully coming out of the fold, come out about 5-10% to a point where little to no “stimulation” is felt from the stretch. Use this final moment to breath into the ‘ease’ of this renewed range of motion.