Kuo C.-CChen S.-CWang J.-YHo T.-JLu T.-W.TUNG-WU LU2022-03-222022-03-22202122964185https://www.scopus.com/inward/record.uri?eid=2-s2.0-85121445280&doi=10.3389%2ffbioe.2021.774771&partnerID=40&md5=da842a9d3f6134e5ec57215e6b553020https://scholars.lib.ntu.edu.tw/handle/123456789/601278Background: Obstacle-crossing increases the risk of falls in older people. This study aimed to identify the effects of long-term Tai-Chi Chuan (TCC) practice on the control strategies for obstacle-crossing in older people. Methods: A multi-objective optimal control technique with measured gait data was used to identify the control strategies adopted by 15 long-term TCC practitioners and 15 healthy controls when crossing obstacles of different heights, in terms of the best-compromise weighting sets for the conflicting objectives of minimizing energy expenditure and maximizing the toe-obstacle and heel-obstacle clearances. Results and Conclusions: The long-term TCC older practitioners adopted a best-compromise control strategy similar to those adopted by young adults, with greater weightings on the minimization of the mechanical energy expenditure and smaller weightings on foot-clearance as compared to non-TCC controls (TCC: 0.72, 0.14, 0.14; Control: 0.55, 0.225, 0.225). This strategy enabled the long-term TCC older practitioners to cross obstacles with significantly greater leading-toe clearances but with relatively less mechanical energy expenditure. With the current approach, further simulations of obstacle-crossing mechanics with a given weighting set will be useful for answering clinically relevant what-if questions, such as what abilities would be needed if the non-TCC older people were to cross obstacles using the crossing strategy of the TCC people. Copyright ? 2021 Kuo, Chen, Wang, Ho and Lu.gait analysisobstacle crossingoptimal controlrisk of fallTai-Chi ChuanRisk assessmentControl strategiesEnergy expenditureFoot clearancesMechanical energiesObstacle crossingsOlder PeopleOptimal controlsRisk of fallTai chisTai-chi chuanGait analysis[SDGs]SDG3[SDGs]SDG7journal article10.3389/fbioe.2021.7747712-s2.0-85121445280