Yoga Basics: How to Keep Your Hamstrings Happy in Forward Bends

Protect your Hamstrings While Doing Yoga!

“Bend your knees!” is a common cue used in yoga classes to protect the back when bending forward. Even though Uttanasana (Standing Forward Fold) is traditionally done with straight legs, many people’s bodies are unable to bend forward from the hips with their knees straight. A forward fold (hinging at the hips with the body hanging perpendicular to the ground) can provide traction to the spine and a nice stretch to the hamstrings. But attempting to bend forward with straight knees may cause harm. In our effort to bow to the sun, we risk overstretching our hamstrings and compromising our intervertebral discs unless we bend our knees.

What Are Hamstrings Anyway?

The hamstrings muscles consist of the semimembranosus, semitendinosus and the biceps femoris. The former two span from the sit bone (ischial tuberosity, which is part of the pelvis) to the inner part of the knee inserting on the shin bone (tibia). The biceps femoris originates at the ischial tuberosity and inserts on the head of the fibula, the outside of knee.

The primary action of the hamstrings is to extend your hip as you flex your knee.  To stretch this muscle, you would do the opposite motion—flex the hip and extend the knee. This is the precise motion we do in asymmetrical forward folds such as Padangustasana (Extended Hand-to-Toe Posture) and Parsvottanasana (Intense Side Stretch).  Forward folds such as Uttanasana do stretch the hamstrings, but not to the extent that asymmetrical forward folds do.

Risks and Hamstring Ahimsa (non-harming)

Asymmetrical forward bends are more challenging to the hamstring group than symmetrical forward bends. This is due to the pelvis moving slightly (and therefore the attachment site of the hamstrings) in opposite directions right and left by the force of opposing muscle groups. These poses include Parivrtta Trikonasana (revolved triangle), Parsvottanasana (intense side stretch) and variations of these poses. These poses are challenging if you have risk factors for hamstring injuries such as hamstring weakness or decreased lumbopelvic stability1.  

The effects of gravity should not be discounted while lowering the body towards the floor. Strength is required to lower your body into forward bending poses rather than simply collapsing.  

The normal range of motion of the hamstring group is 80 to 90 degrees with 90 degrees being a right angle to your torso. Visualize the motion required in Parsvottanasana (Intense Side Stretch Pose). One leg is extended forward, while the other one is two to three feet behind it, knees are straight, and both feet are flat on ground. In this stance you then lengthen the spine forward and attempt to lower the hands toward the floor. When you begin to bend forward in this stance, your front leg will flex well past 90 degrees. To get your hands to the floor (or blocks) while still hinging from the pelvis requires not only greater than normal hamstring flexibility, but also lumbar spine flexibility, strength and the ability to control this movement while moving toward the floor.   

In poses whose names have the word “intense” (utthita in Sanskrit) in them, warm-ups and preparatory poses are essential. I recommend incorporating a variation of a hamstring stretch such as Supta Padangustasana (lying on floor stretching the leg with the knee straight using a strap) as well as other preparatory poses to warm up the body.