It’s a bit of a mouthful – Niralamba badha ardha chandrasana – or “Unsupported bound half-moon pose”, but it’s one of my all-time faves because it’s very accessible and there is loads going on here.
For example, you might be surprised to know that unsupported balance poses like these are a far better way to strengthen and activate your core muscles than doing lots of sit ups. You might also be surprised to know that the moment you hold on to a lifted leg/foot with your hand (as in utthita padangusthasana – standing hand to toe pose) certain trunk muscles will automatically switch off, whereas when your lifted leg is floating in space, you have no choice but to work against gravity and your core becomes naturally more active. If you touch the area around your navel, provided you are relaxed, you should notice that on the lifted side, those muscles are firm and on the standing side, the muscles are soft. This means you can still breathe using the main muscle of breathing – the diaphragm (which is restricted if there is core tension) – and you stay relaxed and calm and don’t end up with a SNS response which reduces the ability of immune system and many others to work efficiently.
You cannot cheat and you cannot over-extend, but certain muscles will lengthen without the feeling of stretch, while others will strengthen without the feeling of tension. For another example, in a pose such as this, you are actually supporting up to 10 times your body weight on the standing limb. It also releases tight hip flexors on the extended leg side because your bum muscles organically switch on. So for core strength, you really can’t beat an unsupported standing balance.