{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,11,6]],"date-time":"2026-11-06T20:47:45Z","timestamp":1793998065084,"version":"4.8.0"},"reference-count":37,"publisher":"JMIR Publications Inc.","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["JMIR Form Res"],"abstract":"Abstract<\/jats:title>\n \n Background<\/jats:title>\n Increasing life expectancy has increased focus on the health-related consequences of aging, such as sarcopenia and frailty. Given the prevalence of these conditions among older individuals and the frequent resulting long-term care needs, early detection and intervention are crucial.<\/jats:p>\n <\/jats:sec>\n \n Objective<\/jats:title>\n This study aimed to validate a novel smartphone-based system measuring acceleration during the sit-to-stand movement to detect sarcopenia and frailty.<\/jats:p>\n <\/jats:sec>\n \n Methods<\/jats:title>\n Participants were 587 individuals from the Otassha study cohort who underwent health assessments in 2023, of whom 569 (96.9%) completed 2 supervised sit-to-stand trials while holding a smartphone on the lower abdomen. Sarcopenia and frailty were diagnosed using the Asian Working Group for Sarcopenia 2019 criteria and the revised Japanese Cardiovascular Health Study criteria, respectively. Peak force, rising time (T1), and stabilization time (T2) were extracted from acceleration signals, and reproducibility was examined using the intraclass correlation coefficient (ICC(2,1)). Predictive models were developed using elastic net penalized logistic regression, and model performance was evaluated using 500 bootstrap resamples. Benchmark models using age and sex, walking speed, and grip strength were also constructed for comparison.<\/jats:p>\n <\/jats:sec>\n \n Results<\/jats:title>\n Sarcopenia and frailty were identified in 16.7% (95\/569) and 9% (51\/569) of the participants, respectively. Peak force demonstrated excellent reliability (ICC=0.863), whereas T1 and T2 showed lower reproducibility (ICC<0.30). For sarcopenia, the smartphone model achieved a bootstrap area under the receiver operating characteristic curve (AUC) of 0.800 and an optimism-corrected AUC of 0.781 (95% CI 0.733\u20100.826), outperforming walking speed (0.663) and age and sex (0.656) and ranking second only to grip strength (0.845). For frailty, the smartphone model showed moderate discrimination, with an optimism-corrected AUC of 0.659 (95% CI 0.587\u20100.736), exceeding age and sex (0.604), whereas walking speed remained the strongest predictor (0.751).<\/jats:p>\n <\/jats:sec>\n \n Conclusions<\/jats:title>\n Smartphone-derived sit-to-stand acceleration provides a practical and scalable approach for screening for sarcopenia and frailty in community-dwelling older adults. While traditional indicators such as grip strength and walking speed remain the most accurate predictors, smartphone-based measurements offer meaningful complementary information and may support large-scale functional screening and early detection initiatives in superaged societies.<\/jats:p>\n <\/jats:sec>","DOI":"10.2196\/83805","type":"journal-article","created":{"date-parts":[[2026,4,6]],"date-time":"2026-04-06T17:11:45Z","timestamp":1775495505000},"page":"e83805-e83805","source":"Crossref","is-referenced-by-count":1,"title":["Validity of Smartphone-Based Measurement for Assessing Lower Limb Power for Sarcopenia and Frailty Discrimination: Cross-Sectional Study"],"prefix":"10.2196","volume":"10","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-0187-9275","authenticated-orcid":false,"given":"Shuichi P","family":"Obuchi","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3015-6041","authenticated-orcid":false,"given":"Hisashi","family":"Kawai","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2356-0188","authenticated-orcid":false,"given":"Takeshi","family":"Kera","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6440-670X","authenticated-orcid":false,"given":"Keigo","family":"Imamura","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3544-4587","authenticated-orcid":false,"given":"Manami","family":"Ejiri","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8329-7617","authenticated-orcid":false,"given":"Hirohiko","family":"Hirano","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3190-0290","authenticated-orcid":false,"given":"Kazushige","family":"Ihara","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8120-6163","authenticated-orcid":false,"given":"Hiroyuki","family":"Sasai","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3384-1696","authenticated-orcid":false,"given":"Yoshinori","family":"Fujiwara","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1010","published-online":{"date-parts":[[2026,4,6]]},"reference":[{"issue":"7721","key":"R1","doi-asserted-by":"publisher","first-page":"45","DOI":"10.1038\/s41586-018-0457-8","article-title":"Facing up to the global challenges of ageing","volume":"561","author":"Partridge","journal-title":"Nature"},{"key":"R2","unstructured":"Annual Health, Labour and Welfare Report 2022. Ministry of Health, Labour and Welfare of Japan; 2022. URL: https:\/\/www.mhlw.go.jp\/english\/wp\/wp-hw15\/index.html [Accessed 22-03-2026]"},{"issue":"6530","key":"R3","doi-asserted-by":"publisher","first-page":"1251","DOI":"10.1136\/bmj.292.6530.1251","article-title":"Elderly patients in acute medical wards: factors predicting length of stay in hospital","volume":"292","author":"Maguire","journal-title":"Br Med J (Clin Res Ed)"},{"issue":"1","key":"R4","doi-asserted-by":"publisher","DOI":"10.1186\/s12877-018-0820-5","article-title":"Age effect on the prediction of risk of prolonged length hospital stay in older patients visiting the emergency department: results from a large prospective geriatric cohort study","volume":"18","author":"Launay","journal-title":"BMC Geriatr"},{"key":"R5","doi-asserted-by":"publisher","DOI":"10.1016\/j.arr.2019.100960","article-title":"Frailty as a predictor of adverse outcomes in hospitalized older adults: a systematic review and meta-analysis","volume":"56","author":"Cunha","journal-title":"Ageing Res Rev"},{"issue":"8","key":"R6","doi-asserted-by":"publisher","first-page":"651","DOI":"10.1038\/s43587-021-00099-3","article-title":"The degree of frailty as a translational measure of health in aging","volume":"1","author":"Howlett","journal-title":"Nat Aging"},{"issue":"4","key":"R7","doi-asserted-by":"publisher","first-page":"412","DOI":"10.1093\/ageing\/afq034","article-title":"Sarcopenia: European consensus on definition and diagnosis: report of the European Working Group on Sarcopenia in Older People","volume":"39","author":"Cruz-Jentoft","journal-title":"Age Ageing"},{"issue":"22","key":"R8","doi-asserted-by":"crossref","first-page":"3029","DOI":"10.1001\/jama.1990.03440220053029","volume":"263","author":"Fiatarone","journal-title":"JAMA"},{"issue":"10206","key":"R9","doi-asserted-by":"publisher","first-page":"1376","DOI":"10.1016\/S0140-6736(19)31785-4","article-title":"Management of frailty: opportunities, challenges, and future directions","volume":"394","author":"Dent","journal-title":"Lancet"},{"issue":"1","key":"R10","doi-asserted-by":"publisher","first-page":"254","DOI":"10.1002\/jcsm.12875","article-title":"Twelve-year sarcopenia trajectories in older adults: results from a population-based study","volume":"13","author":"Trevisan","journal-title":"J Cachexia Sarcopenia Muscle"},{"key":"R11","doi-asserted-by":"publisher","DOI":"10.1016\/j.exger.2018.08.006","article-title":"The sit-to-stand muscle power test: an easy, inexpensive and portable procedure to assess muscle power in older people","volume":"112","author":"Alcazar","journal-title":"Exp Gerontol"},{"key":"R12","doi-asserted-by":"publisher","DOI":"10.1016\/j.jss.2021.01.023","article-title":"Toward remote assessment of physical frailty using sensor-based sit-to-stand test","volume":"263","author":"Park","journal-title":"J Surg Res"},{"issue":"1","key":"R13","doi-asserted-by":"publisher","first-page":"16","DOI":"10.1093\/ageing\/afy169","article-title":"Sarcopenia: revised European consensus on definition and diagnosis","volume":"48","author":"Cruz-Jentoft","journal-title":"Age Ageing"},{"issue":"3","key":"R14","doi-asserted-by":"publisher","first-page":"M146","DOI":"10.1093\/gerona\/56.3.m146","article-title":"Frailty in older adults: evidence for a phenotype","volume":"56","author":"Fried","journal-title":"J Gerontol A Biol Sci Med Sci"},{"key":"R15","doi-asserted-by":"publisher","DOI":"10.1016\/j.gaitpost.2018.01.029","article-title":"Test-retest reliability of daily life gait speed as measured by smartphone global positioning system","volume":"61","author":"Obuchi","journal-title":"Gait Posture"},{"issue":"7","key":"R16","doi-asserted-by":"publisher","first-page":"664","DOI":"10.1111\/ggi.13931","article-title":"Reference value on daily living walking parameters among Japanese adults","volume":"20","author":"Obuchi","journal-title":"Geriatr Gerontol Int"},{"issue":"1","key":"R17","doi-asserted-by":"publisher","first-page":"1","DOI":"10.1519\/JPT.0000000000000099","article-title":"Determining risk of falls in community dwelling older adults: a systematic review and meta-analysis using posttest probability","volume":"40","author":"Lusardi","journal-title":"J Geriatr Phys Ther"},{"issue":"4","key":"R18","doi-asserted-by":"publisher","first-page":"417","DOI":"10.2522\/ptj.20150665","article-title":"Predictive cutoff values of the five-times sit-to-stand test and the timed \"up & go\" test for disability incidence in older people dwelling in the community","volume":"97","author":"Makizako","journal-title":"Phys Ther"},{"key":"R19","doi-asserted-by":"publisher","DOI":"10.1016\/j.exger.2023.112255","article-title":"Sensor- and equation-based sit-to-stand power: the effect of age and functional limitations","volume":"179","author":"Meulemans","journal-title":"Exp Gerontol"},{"issue":"5","key":"R20","doi-asserted-by":"publisher","first-page":"926","DOI":"10.1109\/TNSRE.2014.2331895","article-title":"Kinematic parameters to evaluate functional performance of sit-to-stand and stand-to-sit transitions using motion sensor devices: a systematic review","volume":"22","author":"Millor","journal-title":"IEEE Trans Neural Syst Rehabil Eng"},{"issue":"1","key":"R21","doi-asserted-by":"publisher","first-page":"220","DOI":"10.1016\/j.gaitpost.2014.03.193","article-title":"Test-retest reliability of sensor-based sit-to-stand measures in young and older adults","volume":"40","author":"Regterschot","journal-title":"Gait Posture"},{"key":"R22","doi-asserted-by":"publisher","DOI":"10.1016\/j.gaitpost.2022.02.001","article-title":"Development of a screening formula for sarcopenia using ground reaction force during sit-to-stand motion","volume":"93","author":"Kera","journal-title":"Gait Posture"},{"key":"R23","doi-asserted-by":"publisher","DOI":"10.1016\/j.archger.2020.104221","article-title":"Association between ground reaction force in sit-to-stand motion and falls in community-dwelling older Japanese individuals","volume":"91","author":"Kera","journal-title":"Arch Gerontol Geriatr"},{"key":"R24","doi-asserted-by":"publisher","DOI":"10.1016\/j.jbiomech.2018.06.006","article-title":"Estimation of vertical ground reaction force during running using neural network model and uniaxial accelerometer","volume":"76","author":"Ngoh","journal-title":"J Biomech"},{"issue":"2","key":"R25","first-page":"155","volume":"14","author":"Pouliot-Laforte","journal-title":"J Musculoskelet Neuronal Interact"},{"issue":"4","key":"R26","doi-asserted-by":"publisher","first-page":"403","DOI":"10.1080\/14763141.2013.811284","article-title":"Validity of an upper-body-mounted accelerometer to measure peak vertical and resultant force during running and change-of-direction tasks","volume":"12","author":"Wundersitz","journal-title":"Sports Biomech"},{"issue":"1","key":"R27","doi-asserted-by":"publisher","DOI":"10.1038\/s41746-021-00514-4","article-title":"A systematic review of smartphone-based human activity recognition methods for health research","volume":"4","author":"Straczkiewicz","journal-title":"NPJ Digit Med"},{"issue":"4","key":"R28","doi-asserted-by":"publisher","first-page":"292","DOI":"10.1089\/tmj.2011.0132","article-title":"Reliability and validity of gait analysis by android-based smartphone","volume":"18","author":"Nishiguchi","journal-title":"Telemed J E Health"},{"issue":"1","key":"R29","doi-asserted-by":"publisher","DOI":"10.3390\/s23010192","article-title":"Accelerometers in our pocket: does smartphone accelerometer technology provide accurate data?","volume":"23","author":"Grouios","journal-title":"Sensors (Basel)"},{"key":"R30","doi-asserted-by":"publisher","DOI":"10.3389\/fpubh.2023.1248462","article-title":"Social interaction trajectories and all-cause mortality in older adults: the Otassha study","volume":"11","author":"Kawai","journal-title":"Front Public Health"},{"issue":"7","key":"R31","doi-asserted-by":"publisher","DOI":"10.1371\/journal.pone.0200465","article-title":"Comparison of body composition assessment by DXA and BIA according to the body mass index: a retrospective study on 3655 measures","volume":"13","author":"Achamrah","journal-title":"PLoS One"},{"issue":"3","key":"R32","doi-asserted-by":"publisher","first-page":"300","DOI":"10.1016\/j.jamda.2019.12.012","article-title":"Asian Working Group for Sarcopenia: 2019 consensus update on sarcopenia diagnosis and treatment","volume":"21","author":"Chen","journal-title":"J Am Med Dir Assoc"},{"issue":"10","key":"R33","doi-asserted-by":"publisher","first-page":"992","DOI":"10.1111\/ggi.14005","article-title":"The revised Japanese version of the Cardiovascular Health Study criteria (revised J-CHS criteria)","volume":"20","author":"Satake","journal-title":"Geriatr Gerontol Int"},{"issue":"1","key":"R34","doi-asserted-by":"publisher","DOI":"10.1136\/bmjopen-2022-065098","article-title":"Association between daily life walking speed and frailty measured by a smartphone application: a cross-sectional study","volume":"13","author":"Kawai","journal-title":"BMJ Open"},{"issue":"1","key":"R35","doi-asserted-by":"publisher","DOI":"10.1186\/s12877-022-03042-2","article-title":"Psychosocial factors related to physical activity in frail and prefrail elderly people","volume":"22","author":"Jim\u00e9nez-Zazo","journal-title":"BMC Geriatr"},{"issue":"5","key":"R36","doi-asserted-by":"publisher","first-page":"1333","DOI":"10.1111\/hsc.12781","article-title":"Health promotion for mild frailty based on behaviour change: perceptions of older people and service providers","volume":"27","author":"Avgerinou","journal-title":"Health Soc Care Community"},{"key":"R37","unstructured":"Antonovsky A . Health, Stress, and Coping. Jossey-Bass Incorporated; 1979."}],"container-title":["JMIR Formative Research"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/formative.jmir.org\/2026\/1\/e83805","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,6,30]],"date-time":"2026-06-30T18:17:59Z","timestamp":1782843479000},"score":1,"resource":{"primary":{"URL":"https:\/\/formative.jmir.org\/2026\/1\/e83805"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,4,6]]},"references-count":37,"URL":"https:\/\/doi.org\/10.2196\/83805","relation":{},"ISSN":["2561-326X"],"issn-type":[{"value":"2561-326X","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,4,6]]},"article-number":"v10i7721e83805"}}