Nine is the pole of a number. It is the representative of the peak state. Sanjiu originally referred to solar terms. On the winter solstice, although the weather is still cold, the winter solstice is a sunny day, which is one of the sixty hexagrams. Since then, Yang has been growing. So at this time, practicing martial arts, practicing martial arts, the effect is obvious

Dog days are the hottest season. That's the pole of yang. On the summer solstice, although the weather is very hot, the summer solstice is cloudy. From then on, the yin gradually grows and the yang gradually disappears. At this time, practice can reconcile yin and yang.

Therefore, there is a folk saying, practice three or nine times in winter and three times in summer to test people's perseverance.