Pelvic floor contractions are used in Yoga as part of Pranayama practise- Mula Bandha. The pelvic floor also has an important stabilising function, as it controls the forward and backward movements of the Sacrum – these movements are also called Nutation and Counter Nutation. If the pelvic floor is tight and inelastic, the Sacrum remains tucked (Nutated) in all movements, which can contribute to lower-back pain because a lack of movement here can flatten the natural curve of the lower back.
Use of Mula Bandha does not tighten the Pelvic floor muscles, but helps to keep them strong and elastic. The pelvic floor is inelastic if either the Hip Flexors or Adductor muscles are tight.
Out-dated anatomy textbooks will tell you that the Adductor muscles are only used to bring the legs towards or across the centre-line of the body and that they are weak unless the person either rides horses or is a breast-stroke swimmer. In fact, the adductors are important stabilisers of the legs for all movements and are active as Hip Flexors if the hip is flexed, and are used together with the hamstrings to extend the leg backwards if the hip is extended, and are seldom weak, but often tight.
Tight Adductors also inhibit and weaken Hip Abductor muscles, as explained in Reciprocal Inhibition and the Hips and yoga can contribute to this process, due to the fact that many asanas require the knees to be together, as in Utkatasana, or on top of each other, as in Garudhasana. If Hips are weaker than Adductors, Yogis who are otherwise strong and flexible are unable to sit in Baddha Konasana. Pelvic Floor tightness also occurs if lateral movements of the legs are ignored, but lots of standing splits, Down-dog Splits, Virabhadrasana 3, Dighasana, etc. are practised.
One way in which Adductors and the pelvic floor can be loosened up is to adapt the sequence called ‘Surya Namaskara B’ in the Ashtanga tradition: this sequence is practised as normal, except that Utkatasana is replaced with a conventional squat and Virabhadrasana with a lateral squat. When doing Utkatasana, keep the feet shoulder-width apart, knees facing in the direction of the toes, arms overhead, squat as low as possible, and rise up using a strong contraction of the Glutes. After stepping the leg forward for Virabhadrasana, straighten the front leg and bend the back knee, as you lift your torso, so that you are in a lateral squat position.
Strong yogis may be very surprised at how little lateral flexibility and stability they have in their legs, and should practise this from time to time if they have a problem with tight Adductors and hips.
Franklin, 2004, Conditioning for Dance
Brunnstroms Clinical Kinesiology, 5th edition, 1996