Parivrtta Utkatasana the revolved fierce pose is useful for your balance and strenghening your butt, thighs and back. Come to a chair position, bring your hands to the center of your chest in an isometric pose. Twist your elbo to one knee and breath in and out with your drishti on the sky. Come back to the center, keeping your knees together the best you can. It is ok to shake. Shaking is good it builds the fine muscles needed for balance.
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https://www.youtube.com/watch?v=wZQW8yMF93Y