In yoga, we can imitate this earthbound connection, the rooting quality of body to earth, to discover the ease with which our spines can lengthen and grow. Typically we have either a propped up response to gravity -- very heightened and agitated, a militant straight spine -- or, a very depressed sag toward the earth. There are variations on these themes, of course, but it is helpful to realize we can cultivate a nourishing relationship toward gravity and use that relationship to help our posture and our minds.
Downward-Upward Action
Stand in tadasana and connect with the four corners of your feet. Observe the weight distribution over the four corners and then press them down into the floor. Actively set your roots down. As you do this, what happens to your spine? Do you feel yourself lengthen without force? What about your mind? Does it feel calm? Centred?
Once you have that sense of grounding in tadasana (mountain pose), begin to explore the downward-upward action in urdhva hastasana (upward salute pose).

Urdhva Hastasana
Maintain tadasana, connecting to the pressing down action of the feet. Then, lengthen from your shoulders into your fingertips and bring the arms up alongside the ears. Rotate the upper arms toward the ears to spread the shoulder blades. Once the arms are lifted, observe what happens to your countenance. Did your eyes harden? Do you feel like you have to stretch higher? Then bring your awareness back down into your feet and root them down. As you press down, you naturally feed the upward action of the pose. Root down with the feet. Lengthen up through the arms. Hold for several breaths exploring this relationship.

Again, explore the way the rooting down quality of the pose, fuels and frees up the upward action. If you notice any tension in the face and jaw, find your breath and bring your awareness back into your feet. Hold for several breaths. Release your arms down and step your feet together. Repeat as many times as you like.
Utthita Hasta Padangusthasana
This downward-upward relationship to gravity is helpful in all yoga poses, but particularly useful when we balance on one leg. You can explore the above actions in vrksasana (tree pose) and in the following pose: utthita hasta padangusthasana (big toe hold).
Place a chair against the wall with either the back of the chair or the seat, facing you. (If you have tight hamstrings, start with the foot placed on the chair-seat). Stand in tadasana facing your chair. Connect with the rooting of both feet into the floor. Observe the lift of the trunk. Now, maintain those actions and lift one knee into the body and place the foot on the chair back/seat. You may need the wall to help with your balance. That’s fine. We’re looking for the downward-upward action, so if it’s easier for you to find while holding the wall, do that.
Once your foot is on the chair back/seat, notice if you’ve distorted the standing leg. Often we push the thigh forward and skew the pelvis to lift the foot up. Again, connect to the standing foot and root those four corners down. This should offer you an easy sense of being able to lift the trunk up away from the thigh. Notice if that is true for you. If not, take the foot onto a lower height.

Press through the four corners of the lifted foot. Stretching the whole back of that leg. Now take the arms up into urdva hastasana. Remember to roll the upper arms toward the ears.
Stay several breaths, connecting to the rooted quality through the legs and the lifted quality through the trunk and the arms. If you notice tension in the face, return your awareness to the legs. Seek out the downward quality to feed the pose, rather than completely abandoning yourself to the pain in the back of the legs. Work at a place you can both root down and lengthen up.
To release, bend your knee. Come back to tadasana and repeat on the second side.
Have fun exploring the ways in which you can relate to gravity. And remember, it’s always there and available to you!