Forward-bending postures involve rotating our pelvis up & around the heads of our femurs, creating an anterior pelvic tilt, with less space between the femur, pelvis & lower ribs. This movement serves to lengthen the entire back body all the way from the bottoms of your feet to the fascial connections on the top of your crown. This includes your calf muscles, hamstrings, glutes, the muscles along the spine, & neck.
In our wide-legged forward folds, we also address any tightness or restrictions in our adductors, specifically adductor magnus, “the fourth hamstring”, & its influence on our ability to externally rotate the hip. The strength & flexibility of our quadriceps & hip flexors come into play in poses like supta padangusthasana. Our pelvis is guided into anterior pelvic tilt in this pose as our hamstrings reach their edge in the leg that is being brought to our nose. If our hip flexors are tight in the leg on the floor, it restricts the pelvis from moving back, causing our knee to bend so that the quads relax. Honestly finding our edge in poses that balance in quads & hamstrings is crucial to the authenticity of our practice.
Our abdominals can also assist us in our forward folds both by stabilizing the torso relative to the pelvis & by engaging to deepen the flexion of the spine. However, by contracting these muscles, we can reduce the extension of the spine by creating a posterior pelvic tilt that together with tight hamstrings, may place quite a bit of pressure on the lumbar area of the spine. Abdominal engagement in forward folding poses is often contextual & should be evaluated as an option by the practitioner, their practice, & the pose at hand.