What kind of description does Qi Baishi's freehand brushwork "Being Old and Being Strong" belong to?

Earthworm tracking. When the old man Baishi painted "Being Healthy and Strong", he used a lot of lines, such as scattered front and flying white, and some lines were constantly broken, which really had a charm. Earthworms are used to describe "need to be soft and have bones, and bones are not weak." The pen power is contained, and the pen body is round, so it can be painted with a round pen of seal script. "Qi Baishi, a native of Xiangtan, Hunan Province, is surnamed Huang, who is famous for his life. His nicknames are Baishi, Baishi Weng and Laobai, and his nicknames are Jiping, Laoping, Xieqi, Qida and Mujushi. There are 300 lithographs, and they are modern calligraphers and seal engravers in China.