If you practice too slowly, Qi will stop.Chen Yingjun

I was told this in 2002, when Chen Yingjun saw me practicing the Taijiquan (Tai Chi) old form way too slowly in his backyard.
Chen family Taijiquan (Tai Chi) forms and Chansigong can be practiced in various paces. There’s no ready-made formula, and even the “too slowly” quote above might mean too slowly for me, at that time. The ideal pace depends on a number of factors:

• Which form one is practicing: Paochui Taijiquan (Tai Chi) forms should always be practiced faster than Yilu forms. On the other hand, even fast forms can be practiced fast, or very fast. Some weapon forms also need a minimum speed.
• One’s skill: Yilu forms (both Laojia and Xinjia) gave Taijiquan (Tai Chi) its popular but not so precise image of a slow motion exercise. These forms should be practiced in a relatively slow pace, allowing the student to develop correct body mechanics. But what does relatively slow mean? A Taijiquan (Tai Chi) Master can may perform one Laojia execution in 12 to 15 minutes, without any quality loss, and this would be a slow pace for him. Usually this form takes a student 20 to 30 minutes, but not more than that, except when he’s learning the movements or in special cases.
• One’s fitness level: speed in Taijiquan (Tai Chi) is limited by one’s aerobic prowess and physical strength, as in any sports practice.
• How much one has already practiced on a particular day: the first form executions are always slower than during the rest of the day. The body needs some time to warm up and specially to relax and achieve its best connected state. The speed and power onset may take more or less time, depending on the weather, the quality of sleep in the preceeding night, when the last meal was, etc.

Many variables influence in the ideal speed for practicing Taijiquan (Tai Chi). The fundamental point is you shouldn’t practice so fast that you can’t keep the quality of your posture, and not so slow that Qi won’t circulate fluidly.