Dandasana has the potential to illuminate several key actions in the body essential for deepening the practice of more complex postures. The conscious contraction of the thighs without the help of weight-bearing necessity develops greater control and awareness of the musculature. The action of the arms pressing into the floor lights up the serratus anterior which are important stabilizers of the scapula in arm-supported postures such as Adho Muka Svanasana (Downward Facing Dog) or Chaturanga. The extension of the spine coupled with flexion at the hip reveals tension in the legs and lower back and clearly illuminates the converse relationship between spinal extension and hamstring tension.
This pose may also shed some light on the proportional relationship of the length of the arms versus the torso. Neutral proportions will allow one to plant the hands flat beside the hips with the arms straight and strong without lifting weight out of the sitting bones. Those with proportionally short arms may need to come onto the fingertips, while those with lanky limbs will need to set the hands behind the hips and perhaps bend the elbows to find the appropriate action of the shoulders and spinal extensors.
Ashtangis and those Vinyasa flow yogis among you who are working on jumping through to seated may find it helpful to practice this pose as a way of assessing the suitability of the body for such maneuvers. Those with neutral or long-limbed proportions can rest assured that the jump through will be possible for you with practice. However, if you find that you cannot press the hands flat beside your hips with the arms straight and the spine long, you may need to come to terms with the fact that a pair of blocks can be your friend. No amount of practice will change the proportions of your body. That's a fact, so use the opportunity to practice acceptance and buy yourself a good pair of blocks to set beside your mat.