Fig. 2

Tai Chi lower extremity exercise: Forward Stepping (A): the participant takes a step in the front left direction with the left foot. Once the left heel touches the ground, the participant moves the bodyweight from the right leg to the mid-point in between the feet. Then the participant repeats the movement on the right side. Side Stepping (B): the participant takes a step laterally to the left with the left leg. Once the left toes touch the ground, the participant shifts the bodyweight from the right leg to the left leg. Then the participant repeats the movement on the right side. Backward Stepping (C): the participant takes a step back with the left leg; once the left toe touches the ground, the participant moves the body weight backward from right leg to the left leg while lifting the right heel above the ground and pivoting the right forefoot to face forward. Then the participant repeats the movement on the right side. Turning Stepping (D): the participant takes a step in the front left direction with the left leg and shifts the bodyweight from the left leg to the mid-point between the feet. Then the participant takes a step in the front right direction with the right leg and shifts the bodyweight to the mid-point between the feet. Single-leg Stepping (E): the participant lifts the left leg up over knee height with the ankle slightly plantar flexed. While the left leg is being lifted, the participant fully extends the right knee. Then, the participant maintains this position for 3 s. Then the participant lowers the left leg down to the ground while flexing the right knee. The participant repeats the movement on the right side. Fixing Stepping (F): the participant takes a step to the left direction. Then the participant shifts the body weight between the 2 legs back and forth for 2 times. Then repeats the movement on the right side