{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,2]],"date-time":"2026-03-02T21:15:37Z","timestamp":1772486137402,"version":"3.50.1"},"reference-count":67,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2023,1,5]],"date-time":"2023-01-05T00:00:00Z","timestamp":1672876800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001871","name":"Funda\u00e7\u00e3o para a Ci\u00eancia e a Tecnologia, Portugal","doi-asserted-by":"publisher","award":["2021.08571.BD"],"award-info":[{"award-number":["2021.08571.BD"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Few studies have evaluated the effect of a secondary motor task on the standing posture based on nonlinear analysis. However, it is helpful to extract information related to the complexity, stability, and adaptability to the environment of the human postural system. This study aimed to analyze the effect of two motor tasks with different difficulty levels in motor performance complexity on the static standing posture in healthy young adults. Thirty-five healthy participants (23.08 \u00b1 3.92 years) performed a postural single task (ST: keep a quiet standing posture) and two motor dual tasks (DT). i.e., mot-DT(A)\u2014perform the ST while performing simultaneously an easy motor task (taking a smartphone out of a bag, bringing it to the ear, and putting it back in the bag)\u2014and mot-DT(T)\u2014perform the ST while performing a concurrent difficult motor task (typing on the smartphone keyboard). The approximate entropy (ApEn), Lyapunov exponent (LyE), correlation dimension (CoDim), and fractal dimension (detrending fluctuation analysis, DFA) for the mediolateral (ML) and anterior-posterior (AP) center-of-pressure (CoP) displacement were measured with a force plate while performing the tasks. A significant difference was found between the two motor dual tasks in ApEn, DFA, and CoDim-AP (p &lt; 0.05). For the ML CoP direction, all nonlinear variables in the study were significantly different (p &lt; 0.05) between ST and mot-DT(T), showing impairment in postural control during mot-DT(T) compared to ST. Differences were found across ST and mot-DT(A) in ApEn-AP and DFA (p &lt; 0.05). The mot-DT(T) was associated with less effectiveness in postural control, a lower number of degrees of freedom, less complexity and adaptability of the dynamic system than the postural single task and the mot-DT(A).<\/jats:p>","DOI":"10.3390\/s23020628","type":"journal-article","created":{"date-parts":[[2023,1,5]],"date-time":"2023-01-05T06:11:51Z","timestamp":1672899111000},"page":"628","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":18,"title":["Effects of Motor Task Difficulty on Postural Control Complexity during Dual Tasks in Young Adults: A Nonlinear Approach"],"prefix":"10.3390","volume":"23","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-4446-2894","authenticated-orcid":false,"given":"Marina","family":"Saraiva","sequence":"first","affiliation":[{"name":"RoboCorp Laboratory, i2A, Polytechnic Institute of Coimbra, 3046-854 Coimbra, Portugal"},{"name":"Faculty of Sports, University of Porto, 4200-450 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4109-2939","authenticated-orcid":false,"given":"Jo\u00e3o Paulo","family":"Vilas-Boas","sequence":"additional","affiliation":[{"name":"Faculty of Sports, University of Porto, 4200-450 Porto, Portugal"},{"name":"LABIOMEP-UP, Faculty of Sports and CIFI2D, University of Porto, 4200-450 Porto, Portugal"}]},{"given":"Orlando J.","family":"Fernandes","sequence":"additional","affiliation":[{"name":"Sport and Health Department, School of Health and Human Development, University of \u00c9vora, 7000-671 \u00c9vora, Portugal"},{"name":"Comprehensive Health Research Center (CHRC), University of \u00c9vora, 7000-671 \u00c9vora, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1500-355X","authenticated-orcid":false,"given":"Maria Ant\u00f3nio","family":"Castro","sequence":"additional","affiliation":[{"name":"RoboCorp Laboratory, i2A, Polytechnic Institute of Coimbra, 3046-854 Coimbra, Portugal"},{"name":"Department of Mechanical Engineering, University of Coimbra, CEMMPRE, 3030-788 Coimbra, Portugal"},{"name":"Sector of Physiotherapy, School of Health Sciences, Polytechnic Institute of Leiria, 2411-901 Leiria, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2023,1,5]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"35","DOI":"10.1186\/1475-925X-8-35","article-title":"Study of age-related changes in postural control during quiet standing through Linear Discriminant Analysis","volume":"8","author":"Cavalheiro","year":"2009","journal-title":"Biomed. 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