groupHWHealth and Wellness Education groupTCTai Chi conditionDTODual-task standing condition; two trials: DTO1 and DTO2 conditionQSOEyes-open standing condition; two trials: QSO1 and QSO2 conditionQSCEyes-closed standing condition; two trials: QSC1 and QSC2 Total Duration Total Duration (seconds): total duration captured by the MobilityLab (accelerometer) during standing Total sway area of the accelerometer Total sway area (m^2/s^5): total sway area, computed as the area included in the sway trajectory per unit of time 95% ellipse sway area of the accelerometer 95% ellipse sway area (m^2/s^4): area of the 95% confidence elipse encompassing the sway trajectory in the transerve plane Mean velocity of the accelerometer (AP) Mean velocity (AP) (m/s): mean velocity of the lumbar's trajectory in the anterior-posterior direction Mean velocity of the accelerometer Mean velocity (m/s): mean velocity of the lumbar's trajectory in the transver plane Mean velocity of the accelerometer (ML) Mean velocity (ML) (m/s): mean velocity of the lumbar's trajectory in the medial-lateral direction Mean distance of the acceleration trajectory (AP) Mean distance (AP) (m/s^2): mean distance of the lumbar's acceleration trajectory from the center of this trajectory in the anterior-posterior direction Mean distance of the acceleration trajectory Mean distance (m/s^2): mean distance of the lumbar's acceleration trajectory from the center of this trajectory in the transverse plane Mean distance of the acceleration trajectory (ML) Mean distance (ML) (m/s^2): mean distance of the lumbar's acceleration trajectory from the center of this trajectory in the medial-lateral direction Path length of the acceleration trajectory (AP) Path length (AP) (m/s^2): total length of the lumbar's acceleration trajectory in the anterior-posterior direction Path length of the acceleration trajectory Path length (m/s^2): total length of the lumbar's acceleration trajectory in the transverse plane Path length of the acceleration trajectory (ML) Path length (ML) (m/s^2): total length of the lumbar's acceleration trajectory in the medial-lateral direction