{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,28]],"date-time":"2026-09-28T16:56:17Z","timestamp":1790614577646,"version":"4.1.0"},"reference-count":24,"publisher":"MDPI AG","issue":"19","license":[{"start":{"date-parts":[[2026,9,26]],"date-time":"2026-09-26T00:00:00Z","timestamp":1790380800000},"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>Continuous, objective records of spinal motion during ordinary life have not been available; assessment relies on intermittent questionnaires and brief supervised motion capture. A dual inertial-sensor garment applies the Zero-Cycle method, which organises the differential thorax\u2013pelvis motion into movement cycles and emits one fixed-dimensional feature vector per cycle, using recurrent movement configurations as body-intrinsic anchors. In the implementation used for this study, the differential orientation is projected onto a horizontal plane at a nominal 50 cm scale, centred on a data-derived hub, and segmented at recurrent radial minima; each cycle contributes a start landmark, an apex landmark and their difference, in centimetres of projected radius. No magnetometer is used, and no calibration posture is required at any point. In a four-patient feasibility pilot conducted unsupervised at home around two foraminotomies and two transforaminal epidural steroid injections, 88,027 movement cycles were analysed over 13 to 16 recorded days per patient, across 87 recording-defined sessions during patient-managed home wear. Because home life is unscripted, the principal daily display is Best-200, the lowest-excursion window of 200 consecutive retained cycles observed that day, read as a candidate estimate of the day\u2019s best-controlled state following the best-of-repeated-efforts convention of standardised clinical measurement; whole-day and alternative summaries are reported alongside. The two surgical patients showed a reduction that persisted under every summary rule (cycle-level Cliff\u2019s delta +0.93 and +0.62); the comparison injection case showed no comparable reduction despite substantial improvement in patient-reported outcomes; the index injection case was summary-dependent. Excursion and return-related quantities are motivated by Dubousset\u2019s cone-of-economy and Panjabi\u2019s neutral-zone concepts, without claiming equivalence to either. The contribution is a substrate for machine learning rather than a more accurate sensor; no model is trained and no treatment effect is established.<\/jats:p>","DOI":"10.3390\/s26196102","type":"journal-article","created":{"date-parts":[[2026,9,28]],"date-time":"2026-09-28T15:57:57Z","timestamp":1790611077000},"page":"6102","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Zero-Cycle: First Continuous, Unsupervised, At-Home Monitoring of Spinal Motion as a Per-Cycle Substrate for Machine Learning"],"prefix":"10.3390","volume":"26","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-6781-7013","authenticated-orcid":false,"given":"Grzegorz","family":"Miekisiak","sequence":"first","affiliation":[{"name":"Vratislavia Medica, Lekarska 1, 51-134 Wroc\u0142aw, Poland"}],"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":"data-curation","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0009-0004-4047-9922","authenticated-orcid":false,"given":"Tomasz","family":"Szczepa\u0144ski","sequence":"additional","affiliation":[{"name":"Clinical Department of Neurosurgery, Center for Neurologic Disorders, 4th Military Hospital, Rudolfa Weigla 5, 50-981 Wroc\u0142aw, Poland"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"validation","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"}]},{"given":"Anna","family":"Palczewska","sequence":"additional","affiliation":[{"name":"Vratislavia Medica, Lekarska 1, 51-134 Wroc\u0142aw, Poland"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"investigation","vocabulary":"credit"},{"role":"formal-analysis","vocabulary":"credit"},{"role":"project-administration","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"}]}],"member":"1968","published-online":{"date-parts":[[2026,9,26]]},"reference":[{"key":"ref_1","unstructured":"Weinstein, S.L. (1994). Three-dimensional analysis of the scoliotic deformity. The Pediatric Spine: Principles and Practice, Raven Press."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"390","DOI":"10.1097\/00002517-199212000-00002","article-title":"The stabilizing system of the spine. Part II. Neutral zone and instability hypothesis","volume":"5","author":"Panjabi","year":"1992","journal-title":"J. Spinal Disord."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"383","DOI":"10.1097\/00002517-199212000-00001","article-title":"The stabilizing system of the spine. Part I. Function, dysfunction, adaptation, and enhancement","volume":"5","author":"Panjabi","year":"1992","journal-title":"J. Spinal Disord."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"1124","DOI":"10.1016\/j.spinee.2026.01.025","article-title":"Translating biomechanics to clinic: Validating a spine-specific wearable for remote functional assessment","volume":"26","author":"Haddas","year":"2026","journal-title":"Spine J."},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Filippeschi, A., Schmitz, N., Miezal, M., Bleser, G., Ruffaldi, E., and Stricker, D. (2017). Survey of motion tracking methods based on inertial sensors: A focus on upper limb human motion. Sensors, 17.","DOI":"10.3390\/s17061257"},{"key":"ref_6","unstructured":"Woodman, O.J. (2007). An Introduction to Inertial Navigation, University of Cambridge. Technical Report UCAM-CL-TR-696."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"6007204","DOI":"10.1109\/LSENS.2026.3702726","article-title":"Torso-mounted pedestrian dead reckoning using nadir-based Zero-Cycle heading and differential accelerometry","volume":"10","author":"Miekisiak","year":"2026","journal-title":"IEEE Sens. Lett."},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Farabolini, G., Baldini, N., Pagano, A., Andrenelli, E., Pepa, L., Morone, G., Ceravolo, M.G., and Capecci, M. (2025). Continuous movement monitoring at home through wearable devices: A systematic review. Sensors, 25.","DOI":"10.3390\/s25164889"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"518","DOI":"10.1136\/rapm-2023-104840","article-title":"Wearable motion-based platform for functional spine health assessment","volume":"49","author":"Mageswaran","year":"2024","journal-title":"Reg. Anesth. Pain Med."},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Bailes, A.H., Johnson, M., Roos, R., Clark, W., Cook, H., McKernan, G., Sowa, G.A., Cham, R., and Bell, K.M. (2024). Assessing the reliability and validity of inertial measurement units to measure three-dimensional spine and hip kinematics during clinical movement tasks. Sensors, 24.","DOI":"10.3390\/s24206580"},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"O\u2019Grady, M., O\u2019Dwyer, T., Connolly, J., Condell, J., Esquivel, K.M., O\u2019Shea, F.D., Gardiner, P., and Wilson, F. (2021). Measuring spinal mobility using an inertial measurement unit system: A reliability study in axial spondyloarthritis. Diagnostics, 11.","DOI":"10.3390\/diagnostics11030490"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"e10623","DOI":"10.7717\/peerj.10623","article-title":"A novel IMU-based clinical assessment protocol for axial spondyloarthritis: A protocol validation study","volume":"9","author":"Franco","year":"2021","journal-title":"PeerJ"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"96","DOI":"10.1186\/s12984-024-01366-1","article-title":"Automated, IMU-based spine angle estimation and IMU location identification for telerehabilitation","volume":"21","author":"Pan","year":"2024","journal-title":"J. Neuroeng. Rehabil."},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Riddick, R., Alshehri, M.A., and Hodges, P. (2025). Repeatability of inertial measurements of spinal posture in daily life. Sensors, 25.","DOI":"10.3390\/s25165011"},{"key":"ref_15","unstructured":"CEVA\/Hillcrest Laboratories (2017). BNO080\/BNO085 Data Sheet, CEVA, Inc."},{"key":"ref_16","unstructured":"Sol\u00e0, J. (2017). Quaternion kinematics for the error-state Kalman filter. arXiv."},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Ord\u00f3\u00f1ez, F.J., and Roggen, D. (2016). Deep convolutional and LSTM recurrent neural networks for multimodal wearable activity recognition. Sensors, 16.","DOI":"10.3390\/s16010115"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"91","DOI":"10.1038\/s41746-024-01062-3","article-title":"Self-supervised learning for human activity recognition using 700,000 person-days of wearable data","volume":"7","author":"Yuan","year":"2024","journal-title":"npj Digit. Med."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1145\/3550299","article-title":"Assessing the state of self-supervised human activity recognition using wearables","volume":"6","author":"Haresamudram","year":"2022","journal-title":"Proc. ACM Interact. Mob. Wearable Ubiquitous Technol."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"2940","DOI":"10.1097\/00007632-200011150-00017","article-title":"The Oswestry disability index","volume":"25","author":"Fairbank","year":"2000","journal-title":"Spine"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"319","DOI":"10.1183\/09031936.05.00034805","article-title":"Standardisation of spirometry","volume":"26","author":"Miller","year":"2005","journal-title":"Eur. Respir. J."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"494","DOI":"10.1037\/0033-2909.114.3.494","article-title":"Dominance statistics: Ordinal analyses to answer ordinal questions","volume":"114","author":"Cliff","year":"1993","journal-title":"Psychol. Bull."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"148","DOI":"10.1007\/s005860050045","article-title":"Testing criteria for spinal implants: Recommendations for the standardization of in vitro stability testing of spinal implants","volume":"7","author":"Wilke","year":"1998","journal-title":"Eur. Spine J."},{"key":"ref_24","first-page":"1","article-title":"Activity recognition from user-annotated acceleration data","volume":"Volume 3001","author":"Ferscha","year":"2004","journal-title":"Pervasive Computing (PERVASIVE 2004)"}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/26\/19\/6102\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,9,28]],"date-time":"2026-09-28T15:59:20Z","timestamp":1790611160000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/26\/19\/6102"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,9,26]]},"references-count":24,"journal-issue":{"issue":"19","published-online":{"date-parts":[[2026,10]]}},"alternative-id":["s26196102"],"URL":"https:\/\/doi.org\/10.3390\/s26196102","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,9,26]]}}}