{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,2]],"date-time":"2026-07-02T12:25:26Z","timestamp":1782995126574,"version":"3.54.5"},"reference-count":39,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2018,4,5]],"date-time":"2018-04-05T00:00:00Z","timestamp":1522886400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Parkinson\u2019s disease (PD) can be divided into two subtypes based on clinical features\u2014namely tremor dominant (TD) and postural instability and gait difficulty (PIGD). This categorization is important at the early stage of PD, since identifying the subtypes can help to predict the clinical progression of the disease. Accordingly, correctly diagnosing subtypes is critical in initiating appropriate early interventions and tracking the progression of the disease. However, as the disease progresses, it becomes increasingly difficult to further distinguish those attributes that are relevant to the subtypes. In this study, we investigated whether a method using the standing center of pressure (COP) time series data can separate two subtypes of PD by looking at the frequency component of COP (i.e., COP position and speed). Thirty-six participants diagnosed with PD were evaluated, with their bare feet on the force platform, and were instructed to stand upright with their arms by their sides for 20 s (with their eyes open and closed), which is consistent with the traditional COP measures. Fast Fourier transform (FFT) and wavelet transform (WT) were performed to distinguish between the motor subtypes using the COP measures. The TD group exhibited larger amplitudes at the frequency range of 3\u20137 Hz when compared to the PIGD group. Both the FFT and WT methods were able to differentiate the subtypes. COP time series information can be used to differentiate between the two motor subtypes of PD, using the frequency component of postural stability.<\/jats:p>","DOI":"10.3390\/s18041102","type":"journal-article","created":{"date-parts":[[2018,4,5]],"date-time":"2018-04-05T16:50:58Z","timestamp":1522947058000},"page":"1102","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":27,"title":["Motor Subtypes of Parkinson\u2019s Disease Can Be Identified by Frequency Component of Postural Stability"],"prefix":"10.3390","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-4500-5692","authenticated-orcid":false,"given":"Saba","family":"Rezvanian","sequence":"first","affiliation":[{"name":"School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ 85281, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7008-5711","authenticated-orcid":false,"given":"Thurmon","family":"Lockhart","sequence":"additional","affiliation":[{"name":"School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ 85281, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Christopher","family":"Frames","sequence":"additional","affiliation":[{"name":"School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ 85281, USA"},{"name":"Barrow Neurological Institute, Phoenix, AZ 85013, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9836-1549","authenticated-orcid":false,"given":"Rahul","family":"Soangra","sequence":"additional","affiliation":[{"name":"Department of Physical Therapy, Crean College of Health and Behavioral Sciences, Chapman University, Orange, CA 92866, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Abraham","family":"Lieberman","sequence":"additional","affiliation":[{"name":"Barrow Neurological Institute, Phoenix, AZ 85013, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2018,4,5]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"311","DOI":"10.1002\/mds.25292","article-title":"The current and projected economic burden of Parkinson\u2019s disease in the United States","volume":"28","author":"Kowal","year":"2013","journal-title":"Mov. 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