The interface between the practice of forms and combat in tai chi is known as pushing hands – a repetitive two-person exercise. The idea is to build up sensitivity to the shifting weight of the opponent and to use this against them – pretty much as in judo and aikido.
In real life, when the push/strike comes, you parry this to one side and then smite the opponent with
destruction, or side-step and walk away in a spirit of forgiveness – depending on your Testament preferences. However, practising such single strikes means constant realignment – and precludes the kind of repetition which converts a technique into a reflex. So the end of the process is modified allowing a repeated circular practice to take place.There is a parallel to this in the practice of tricky passages of music. Often, the problem is caused by only a few notes – let’s say five for the sake of the argument. Playing the five notes once through will not bring about much improvement. Creating a loop of the notes is the solution. However, sometimes, the journey from the 5th note to the 1st introduces a new difficulty which doesn’t even feature in the piece. At this point the modification kicks in and an easy note (usually an open string) is inserted. Pupils play the new six-note loop until the problem has disappeared. One difference between a junior and a senior pupil is that, while a junior pupil can understand and practise the loop, a senior pupil should be able identify where one would be useful and to create it.