Stand upright with your feet shoulder-width apart, toes slightly in. (Take your shoes off so you can feel the floor under you.) Press into your feet as if you were trying to push the floorboards apart between your feet. You will feel a solidity come into your legs as you do this. This comes from pushing down into your feet.
Once you can feel that solidity, you are ready to begin the exercise. Inhale deeply and bend your knees, letting your belly relax. Now exhale and push into your feet s-l-o-w-l-y, pushing as you did before and allowing your legs to slowly straighten. Do not let them straighten all the way, but bend them again and inhale as you go down into your legs. Push again against the floor as you exhale, pushing your energy downward through your body.
Do not completely straighten your legs, keep breathing, and move slowly. If you are doing this correctly, you will start to feel a slow vibration in your legs as you push against the floor. This vibration is the charge of energy moving through your legs and into your first chakra. It can be used to push out blocks, to increase your sense of contact with your body, or to simply make you feel awake and refreshed.
It is possible to get overcharged, however, so exercise caution in how long you keep this up. If you get overcharged and feel anxious, kick your feet into a pile of pillows, shake your body, or let out whatever feelings are arising.
