{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,23]],"date-time":"2026-10-23T21:11:27Z","timestamp":1792789887174,"version":"4.5.0"},"reference-count":32,"publisher":"MDPI AG","issue":"19","license":[{"start":{"date-parts":[[2026,9,22]],"date-time":"2026-09-22T00:00:00Z","timestamp":1790035200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100018488","name":"Boston University Clinical and Translational Science Institute","doi-asserted-by":"publisher","award":["1UL1TR001430"],"award-info":[{"award-number":["1UL1TR001430"]}],"id":[{"id":"10.13039\/100018488","id-type":"DOI","asserted-by":"publisher"}]},{"award":["1UL1TR001430"],"award-info":[{"award-number":["1UL1TR001430"]}],"id":[{"id":"https:\/\/ror.org\/04hs54263","id-type":"ROR","asserted-by":"publisher"}]},{"name":"National Institutes of Health","award":["R21HD111945"],"award-info":[{"award-number":["R21HD111945"]}]},{"name":"National Institutes of Health","award":["F32HD117600"],"award-info":[{"award-number":["F32HD117600"]}]},{"award":["R21HD111945"],"award-info":[{"award-number":["R21HD111945"]}],"id":[{"id":"https:\/\/ror.org\/01cwqze88","id-type":"ROR","asserted-by":"publisher"}]},{"award":["F32HD117600"],"award-info":[{"award-number":["F32HD117600"]}],"id":[{"id":"https:\/\/ror.org\/01cwqze88","id-type":"ROR","asserted-by":"publisher"}]},{"name":"Boston University","id":[{"id":"https:\/\/ror.org\/05qwgg493","id-type":"ROR","asserted-by":"crossref"}]},{"id":[{"id":"https:\/\/ror.org\/05qwgg493","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Background: Quantifying movement during early mobility interventions is important for evaluating intervention participation and progression in toddlers with Down syndrome (DS), but behavioral video coding is time and labor-intensive. This study established and evaluated an activity count cutpoint for distinguishing moderate-to-vigorous physical activity (MVPA) and sedentary-to-light physical activity (SLPA) in toddlers with DS during a home-based mobility intervention using a wearable accelerometer integrated into a body-weight support harness system. Methods: Video recordings behaviorally coded for MVPA and SLPA were synchronized with accelerometer activity counts binned in 5 s epochs. Receiver operating characteristic curve analysis was used to determine both group-derived and participant-specific activity count cutpoints. Results: The optimal group-derived cutpoint was 141 activity counts per 5 s, demonstrating strong classification performance (AUC = 0.903), with 94.4% sensitivity, 70.2% specificity, and an overall classification accuracy of 79.2%. Participant-specific cutpoints resulted in only minimal improvements in classification performance. Conclusions: These findings suggest that using individualized cutpoints may not be necessary for classifying MVPA in toddlers with DS during this intervention, though replication in a larger sample is warranted. A standardized activity count cutpoint may provide a practical approach for objectively monitoring activity during home-based mobility interventions.<\/jats:p>","DOI":"10.3390\/s26196002","type":"journal-article","created":{"date-parts":[[2026,9,22]],"date-time":"2026-09-22T15:28:43Z","timestamp":1790090923000},"page":"6002","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Quantifying Physical Activity in Toddlers with Down Syndrome with Wearable Sensors During a Home-Based Mobility Intervention"],"prefix":"10.3390","volume":"26","author":[{"ORCID":"https:\/\/orcid.org\/0009-0007-9982-0824","authenticated-orcid":false,"given":"Varsha","family":"Athreya","sequence":"first","affiliation":[{"name":"Department of Computer Engineering, Boston University, Boston, MA 02215, USA"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"methodology","vocabulary":"credit"},{"role":"software","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"},{"role":"formal-analysis","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"},{"role":"visualization","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0009-0004-8389-8748","authenticated-orcid":false,"given":"Simoni","family":"Mishra","sequence":"additional","affiliation":[{"name":"Department of Biomedical Engineering, Boston University, Boston, MA 02215, USA"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"methodology","vocabulary":"credit"},{"role":"software","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"},{"role":"formal-analysis","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"},{"role":"visualization","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6002-3667","authenticated-orcid":false,"given":"Ashley N.","family":"Collimore-Doherty","sequence":"additional","affiliation":[{"name":"Department of Physical Therapy, Boston University, Boston, MA 02215, USA"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"methodology","vocabulary":"credit"},{"role":"software","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"},{"role":"formal-analysis","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"},{"role":"visualization","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9883-8471","authenticated-orcid":false,"given":"Ellen N.","family":"Sutter","sequence":"additional","affiliation":[{"name":"Department of Physical Therapy, Boston University, Boston, MA 02215, USA"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"methodology","vocabulary":"credit"},{"role":"software","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"},{"role":"formal-analysis","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"},{"role":"visualization","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9160-7825","authenticated-orcid":false,"given":"Jana M.","family":"Iverson","sequence":"additional","affiliation":[{"name":"Department of Physical Therapy, Boston University, Boston, MA 02215, USA"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"},{"role":"project-administration","vocabulary":"credit"},{"role":"funding-acquisition","vocabulary":"credit"}]}],"member":"1968","published-online":{"date-parts":[[2026,9,22]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"e1626","DOI":"10.1002\/wcs.1626","article-title":"Developing language in a developing body, revisited: The cascading effects of motor development on the acquisition of language","volume":"13","author":"Iverson","year":"2022","journal-title":"Wiley Interdiscip. Rev. Cogn. Sci."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"346","DOI":"10.1111\/jir.12580","article-title":"A schedule of gross motor development for children with Down syndrome","volume":"63","author":"Winders","year":"2019","journal-title":"J. Intellect. Disabil. Res."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"e2023065402","DOI":"10.1542\/peds.2023-065402","article-title":"Developmental Milestones for Children with Down Syndrome","volume":"154","author":"Baumer","year":"2024","journal-title":"Pediatrics"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"e2022057010","DOI":"10.1542\/peds.2022-057010","article-title":"Health Supervision for Children and Adolescents with Down Syndrome","volume":"149","author":"Bull","year":"2022","journal-title":"Pediatrics"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"894","DOI":"10.1016\/j.ridd.2012.11.021","article-title":"Infants with Down syndrome: Percentage and age for acquisition of gross motor skills","volume":"34","author":"Pereira","year":"2013","journal-title":"Res. Dev. Disabil."},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Paleg, G.S., Hidalgo Robles, \u00c1., Govender, P., and Livingstone, R.W. (2025). Occupational and Physical Therapy Interventions for Young Children with Developmental Central Hypotonia: An Overview of Systematic Reviews. Disabilities, 5.","DOI":"10.3390\/disabilities5010014"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"2","DOI":"10.1097\/PEP.0000000000001067","article-title":"Informing Clinical Practice Guidelines for Children and Youth with Down Syndrome: A Survey of Key Partners","volume":"36","author":"Wentz","year":"2024","journal-title":"Pediatr. Phys. Ther."},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Hospodar, C.M., Enriques, F.A., Paez, A.I., Feldner, H.A., Looper, J.E., and Kretch, K.S. (2026). Overground suspension walkers elicit more and higher quality stepping than treadmills: A longitudinal study of pre-walking infants with Down syndrome. openRxiv.","DOI":"10.64898\/2026.05.05.26352150"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"839","DOI":"10.1111\/j.1469-8749.2007.00839.x","article-title":"Exploring effects of different treadmill interventions on walking onset and gait patterns in infants with Down syndrome","volume":"49","author":"Wu","year":"2007","journal-title":"Dev. Med. Child Neurol."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"E76","DOI":"10.1097\/PEP.0000000000000752","article-title":"In-Home Mobility Training with a Portable Body Weight Support System of an Infant with Down Syndrome","volume":"32","author":"Kokkoni","year":"2020","journal-title":"Pediatr. Phys. Ther."},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Pedersen, M.R.L., and Hansen, A.F. (2022). Interventions by Caregivers to Promote Motor Development in Young Children, the Caregivers\u2019 Attitudes and Benefits Hereof: A Scoping Review. Int. J. Environ. Res. Public Health, 19.","DOI":"10.3390\/ijerph191811543"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"243","DOI":"10.1016\/j.jphys.2021.08.016","article-title":"Physiotherapy management of Down syndrome","volume":"67","author":"Shields","year":"2021","journal-title":"J. Physiother."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"zae125","DOI":"10.1093\/ptj\/pzae125","article-title":"Type and Distribution of Gross Motor Activity During Physical Therapy in Young Children with Cerebral Palsy","volume":"104","author":"Prosser","year":"2024","journal-title":"Phys. Ther."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"3312","DOI":"10.1007\/s10826-017-0826-1","article-title":"Mothers\u2019 Experiences of Parent-Reported and Video-Recorded Observational Assessments","volume":"26","author":"Bennetts","year":"2017","journal-title":"J. Child Fam. Stud."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"43","DOI":"10.1186\/s12966-024-01596-5","article-title":"Reliability and validity of rapid assessment tools for measuring 24-hour movement behaviours in children aged 0\u20135 years: The Movement Behaviour Questionnaire Baby (MBQ-B) and child (MBQ-C)","volume":"21","author":"Trost","year":"2024","journal-title":"Int. J. Behav. Nutr. Phys. Act."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"e17216","DOI":"10.2196\/17216","article-title":"Development and Clinical Evaluation of a Web-Based Upper Limb Home Rehabilitation System Using a Smartwatch and Machine Learning Model for Chronic Stroke Survivors: Prospective Comparative Study","volume":"8","author":"Chae","year":"2020","journal-title":"JMIR mHealth uHealth"},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Komaris, D.S., Tarfali, G., O\u2019Flynn, B., and Tedesco, S. (2022). Unsupervised IMU-based evaluation of at-home exercise programmes: A feasibility study. BMC Sports Sci. Med. Rehabil., 14.","DOI":"10.1186\/s13102-022-00417-1"},{"key":"ref_18","first-page":"100445","article-title":"Quantifying At-Home Physiotherapy Participation: SPARS vs Self-Reported Diaries","volume":"7","author":"Rezkalla","year":"2025","journal-title":"Arch. Rehabil. Res. Clin. Transl."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"2317","DOI":"10.1038\/oby.2011.364","article-title":"Identification and validity of accelerometer cut-points for toddlers","volume":"20","author":"Trost","year":"2012","journal-title":"Obesity"},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Orlando, J.M., Smith, B.A., Hafer, J.F., Paremski, A., Amodeo, M., Lobo, M.A., and Prosser, L.A. (2025). Physical Activity in Pre-Ambulatory Children with Cerebral Palsy: An Exploratory Validation Study to Distinguish Active vs. Sedentary Time Using Wearable Sensors. Sensors, 25.","DOI":"10.3390\/s25041261"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"101142","DOI":"10.1016\/j.pmedr.2020.101142","article-title":"Calibration and validation of accelerometry using cut-points to assess physical activity in paediatric clinical groups: A systematic review","volume":"19","author":"Bianchim","year":"2020","journal-title":"Prev. Med. Rep."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"92","DOI":"10.1016\/j.jsams.2023.11.008","article-title":"Calibration and validation of physical behaviour cut-points using wrist-worn ActiGraphs for children and adolescents: A systematic review","volume":"27","author":"Clanchy","year":"2024","journal-title":"J. Sci. Med. Sport"},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"McGarty, A.M., Penpraze, V., and Melville, C.A. (2016). Calibration and Cross-Validation of the ActiGraph wGT3X+ Accelerometer for the Estimation of Physical Activity Intensity in Children with Intellectual Disabilities. PLoS ONE, 11.","DOI":"10.1371\/journal.pone.0164928"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"14","DOI":"10.1186\/s12966-020-0912-4","article-title":"Infants\u2019 and toddlers\u2019 physical activity and sedentary time as measured by accelerometry: A systematic review and meta-analysis","volume":"17","author":"Bruijns","year":"2020","journal-title":"Int. J. Behav. Nutr. Phys. Act."},{"key":"ref_25","first-page":"160","article-title":"Early Movement Matters: Interplay of Physical Activity and Motor Skill Development in Infants with Down Syndrome","volume":"37","author":"Hauck","year":"2020","journal-title":"Adapt Phys. Act. Q."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"227","DOI":"10.1007\/BF01046967","article-title":"Motor control in Down syndrome: The role of adaptation and practice","volume":"4","author":"Latash","year":"1992","journal-title":"J. Dev. Phys. Disabil."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"229","DOI":"10.3200\/JMBR.38.3.229-237","article-title":"Early stage of walking: Development of control in mediolateral and anteroposterior directions","volume":"38","author":"Kubo","year":"2006","journal-title":"J. Mot. Behav."},{"key":"ref_28","doi-asserted-by":"crossref","unstructured":"Collimore-Doherty, A.N., Sutter, E.N., Wilkerson, E., Baumer, N.T., and Iverson, J.M. (2026). Implementation and acceptability of PUMA Playtime intervention for toddlers with Down syndrome: A feasibility study. Disabil. Rehabil. Assist Technol., 1\u201312.","DOI":"10.1080\/17483107.2026.2716555"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"11958","DOI":"10.1038\/s41598-022-16003-x","article-title":"Quantification of acceleration as activity counts in ActiGraph wearable","volume":"12","author":"Neishabouri","year":"2022","journal-title":"Sci. Rep."},{"key":"ref_30","doi-asserted-by":"crossref","unstructured":"Ferry, J.M., Escribano, J., Gispert, L.M., Koletzko, B., and Grote, V. (2025). Impact of cut-point methods on classification of physical activity and sedentary behaviour of toddlers. BMC Public Health, 25.","DOI":"10.1186\/s12889-025-24636-6"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"31","DOI":"10.1186\/s12984-024-01327-8","article-title":"Emerging methods for measuring physical activity using accelerometry in children and adolescents with neuromotor disorders: A narrative review","volume":"21","author":"Petersen","year":"2024","journal-title":"J. Neuroeng. Rehabil."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"102199","DOI":"10.1016\/j.infbeh.2026.102199","article-title":"Characterizing infant leg movements using 72-h wearable sensor data: Descriptive analysis from a large, heterogenous sample of infants 0-2 months of age from the HEALthy Brain and Child Development Study","volume":"84","author":"Oh","year":"2026","journal-title":"Infant Behav. Dev."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/26\/19\/6002\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,9,24]],"date-time":"2026-09-24T04:14:48Z","timestamp":1790223288000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/26\/19\/6002"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,9,22]]},"references-count":32,"journal-issue":{"issue":"19","published-online":{"date-parts":[[2026,10]]}},"alternative-id":["s26196002"],"URL":"https:\/\/doi.org\/10.3390\/s26196002","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,9,22]]}}}