Those yoga practitioners with tense hamstrings are the ones most likely to tense up in poses meant to release the hams and they then lose the benefit of the pose. Uttanasana (Standing Forward Bend) is a pose where to experience a relaxing stretch in your back, neck and legs, you must release the hamstrings.
Uttanasana is often used as a relaxing break after standing poses or as a rest during an intense vinyasa sequence. When performing the Standing Forward Bend, it is best to stretch the hamstrings on the back of your thighs and contract the quadriceps on the front of your thighs. In Uttanasana, positioning is important to allow the hamstrings to lengthen and relax into the stretch as opposed to holding on tightly and contracting.
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To appreciate how your hamstrings work in Uttanasana, it is important to understand the three distinct forms of muscle contraction. In an isometric contraction, the muscle does not change length; a concentric contraction makes the muscle shorter; and an eccentric contraction lengthens the muscle.
If you start in Uttanasana with your knees straight and your pelvis tilted forward so that your head and spine are moving towards the floor, as you come up out of the pose, the hamstrings contract and pull down the sitting bones. The pelvis will then move upright and the upper body aligns with the legs. The hamstrings have performed a concentric, or shortening, contraction.
However, when standing and tilting the pelvis forward the hamstrings perform a lengthening, or eccentric contraction. If you stop halfway, the hamstrings will perform an isometric contraction. They are still working hard, but are neither shortening nor lengthening. Here is the problem for students with tight hamstrings: they cannot reach their fingers to the floor so when they bend over they end up sort of "stuck" halfway - and in an isometric contraction.
It is not recommended that Uttanasana be practiced with the fingers dangling towards the ground. This puts undue pressure on the muscles as well as the lower back. The hamstrings will not benefit and become more flexible, but remain rigid.
A simple solution is to put a yoga block or a folded blanket under your hands to support the weight of your body through your arms. The hamstrings will then no longer be required to support the torso and can lengthen and relax.
For proper alignment in this pose, ensure that the hips are over your ankles, not behind them. The knees should be straight. To offset the tendency to bend the knees, the quadriceps should be contracted. Since they are "antagonistic" muscle groups, the hamstrings will automatically relax when you flex your quads. This will allow for a fuller stretch of the hamstrings.
The Standing Forward Bend is also excellent work for the erector spinae, the group of small muscles that run up and down the spine. Just as with the hamstrings, the erector spinae will only benefit from this pose if the weight of the upper body is supported by placing the hands on the floor or a prop.
Remember to keep the quads working. With time and practice, the hamstrings will lengthen and release, allowing further release in the lower back and pelvic region.
Yoga: Firm Your Quads and Release Your Hamstrings
Michael Russell Your Independent guide to Yoga