倒立之弊
从头倒立，手倒立到各种花样倒立，到运用工具的所谓反重力倒挂已经充满的市场；瑜伽老师以及许多瑜伽习练者也纷纷积极练习。“头倒立”被称为“瑜伽体位之王”，它有它的好处并也已经广为传颂，不必赘述。但任何事物都是有两面性的，这里就着重谈谈倒立倒挂等体位的弊端，希望大家能有一个参考。
人类自从开始双脚行走后，在进化中，我们的脊柱就已经区别于其他脊椎动物。由于我们的下肢要承受越来越大的压力（当我们慢慢进化成双足站立的动物），所以人类的脊柱变得颈椎最细，从胸椎到腰椎到骶骨越来越粗（尾骨已经退化成一个小尖尖）。在物理中有个普遍认知，想必大家也都能领会：面积越大，压力越小，所能承受的压力相对比较大；面积越小，压力越大，所能承受的压力也就相对较小。人类的脊柱从上到下，从颈椎到骶骨，随着压力的增大，是越来越粗的，就是为了能够让我们的腰椎和骶骨有足够大的面积去承受逐渐递增的压力。
那么如果我们把它倒过来，头在下脚在上。相对于上肢，我们的下肢又长又重，把这样一股压力，压在面积细小的胸椎和颈椎上，你再怎么有核心力量，颈椎和胸椎的压力已经被无故增强，何况大多数练习者没有那么强的核心力量或者不会用那股核心力量，那么脊椎和脊髓神经受伤或被压迫的风险就会增大。另外，我们是无法阻止大量血液受地心引力牵引的力量的。我们直立行走，血液正常循环，血管的瓣膜会阻止血液逆行；但当我们倒立倒挂时，会不可避免的打扰血液循环的正常路径，后果就不太好说。因为迄今为止，我们谁也不敢讲我们对人体构造有百分之百的把握。
脊柱中的脊髓，是大脑的延伸，大脑和脊髓组成人体中枢神经系统，执掌整个人体的功能运作，情绪和感官力；在中医里，它是“诸阳之主”督脉，掌管一身阳气。阳，就是生命里啊！所以，不要轻易玩火。其实倒立的一些好处，很多其他简单的，不易受伤的体位也可以达到。
这里只希望大家可以一分为二的看待倒立倒挂这类“高级”体位，不要随便跟风随大流。
The Adversary of Head Standing
Head standing, hand standing and anti-gravity postures are very popular. Are they really good for our health? Maybe. However, their adversary is definite.
Millions of years of evolution gave our spine a very special point different from other vertebrates. Our spine is thinner at the cervical vertebra area and much thicker at the lumbar vertebra area transited by medium sized thoracic vertebrae. However, other vertebrates like cats or dogs, their spine has almost the same width from top to bottom. The reason for this difference is we stand and walk using two feet, not four. The lumbar vertebrae are much thicker to have enough space to spread the pressure given by the entire upper body.
Like head standing sorts of postures, you lift your legs up and no matter how much core strength you have, you still cannot change the fact you are giving the wrong level of pressure to your delicate thoracic and cervical vertebrae. Moreover, most of the practitioners don’t have enough or don’t know how to use core strength. Therefore, the risk of getting injured in thoracic or cervical vertebra area is much higher. Besides, we have this one-direction valve in our vinery system which can prevent blood circulating in a wrong direction. When we put our body upside down, for a short while, it is not going to be a big problem but if you keep doing it for minutes, no one can promise where the gravity is going to lead the blood which could cause server damage in your nervous system.
In Chinese medicine theory, brain and spinal cords are consist of the Governor Channel which is in charge of the life force of a human body. It has its own flow direction, so don’t mess with it. Moreover, we need to learn to listen to our body. If you feel great difficulty or fear do to head standing sorts of poses, that means your body is not ready, so don’t be hasty. If you do enjoy those poses, just remember the time limit, don’t overdo it.
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