During the experiment, 1 researcher was responsible for recording videos and the other was responsible for collecting plantar pressure. In order to prevent the shake of clothes from affecting the accuracy of experimental data, subjects were asked to wear black tights. At the same time, in order to ensure the accuracy of plantar pressure measurement, and the subjects completed the STS movement without wearing the shoes. To obtain kinematic data, red markers were attached to the following anatomical landmarks on the left side of the subject’s body: shoulder, waist, knee, hip, and ankle joints. The waist point is located at 60% of the line between the shoulder joint and the hip joint. Subjects were seated on the seat of an armless, backless chair, which was adjusted to 100% of each subject’s knee height. Subjects were instructed to fold their arms across the chest and to rise without bringing their arms forward. Subjects began to perform STS transfer at the word “start,” at the same time, the researchers turned on video recording and begin to measure plantar pressure. The movement ended with the subject’s self-report “stop,” at the moment, and researchers finished the data collection and checked whether there were any incorrect data. Subjects performed the STS task at natural (self-selected) speed. Four different experimental conditions of IFAs were set: Nature (N), 0°(U0), 15°(U15), 30°(U30). Data were collected for 2 trials for each subject. Subjects were given adequate rest between trials to avoid fatigue. We defined the time to complete the STS as T under each condition of IFAs.
In the process of experiment, the bias mainly came from the subject, the researcher who carried out the experiment and the measurement process, and so we paid special attention to control the possible bias factors in the experimental process to ensure the accuracy and reliability of the measurement results.