Eight Five form (八五式) should be a core practice for any serious Yang style Tai Chi practitioners. There are two quite different approach in its practice:
- Xu Tui method (虚腿式): When practicing this method, you shift the weight away from the supporting/turning leg before turning your waist/leg.
- Shi Tui method (实腿式): When practicing this method, you turn your waist/leg with your weight on that supporting/turning leg.
The difference between the two methods impacts on a lot of moves such as “Raising Hand and Stepping Up” (提手上势), “Left and Right Brush Knee” (左右搂膝抝步), “Step Forward, Parry, Block, and Punch” (进步搬拦捶), “Cross Hands” (十字手) etc.
There are big debates in China arguing which training method is right. Personally, I think it is pointless as both methods are fine and there are well known masters who specialise in either one of them.
Zheng Man Qing (郑曼青), Yang Zhen Ji (杨振基) (2nd son of Grandmaster Yang Chen Fu), Li Tian Ji (李天骥) (the creator of 24 simplified form) etc. are the masters who practice Xu Tui method (虚腿式), while Grandmaster Yang Cheng Fu (杨澄甫) in his 1933 book, Fu Zhong Wen (傅钟文), Li Ya Xuan (李雅轩) etc. showed their form in Shi Tui method (实腿式)
I have practiced both methods myself for quite a long time and have now settled on Xu Tui method (虚腿式). My own experience and research leads me to believe that the two training methods have different approaches to yielding. Xu Tui method (虚腿式) trains yielding with movement. You do not engage the force but move with the force. In Chinese, it’s called Gudang jin (鼓荡劲). This perhaps is better suited for smaller and light build practitioners. Shi Tui method (实腿式) emphasises on turning without moving the centre. You yield with turning the force away. In Chinese, it’s called Gu jin (固劲). It may be more suitable for bigger and strong build practitioners.
You should experience both yourself at certain stage of your development. But do seek proper guidance, especially in training Shi Tui method (实腿式), as incorrect practicing could result in knee injury.