Grandmaster Yang Cheng Fu described in his book, “The Practice of Taijiquan”, that “the two legs be differentiated into yin and yang, and should raise and lower as if walking like a cat”.
"The Taiji Classics state that “if the hands advance three percent, then the legs advance seven percent”. This demonstrates the importance of stance work and stepping in Taijiquan. There is also a saying which says that if one can perform a proper “Taiji Cat Walk”, it does not necessarily mean one’s Taijiquan is good, but in order to be very good at Taijiquan, one must have a proper “Taiji Cat Walk”. The legs move slowly and evenly under the control of the waist and spine while performing the “Taiji Cat Walk”. Close to half of the largest muscles groups found within the body are below the waist and abdomen. The “Taiji Cat Walk” will allow all the muscles, ligaments, joints, etc. to obtain maximum range of exercise with the least amount of resistance. The action which occurs in the legs is similar to the motion of twisting (draining) a wet towel. All of the fibers within the towel (legs) will receive varying degrees of twisting and pressure."
Tai Chi Chuan Journal, Volume 4, Number 3, Summer 2003, "Walk Like a Cat" by Greta Hill.
Walking and Tai Chi Chuan