{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T09:17:07Z","timestamp":1785403027440,"version":"3.56.0"},"reference-count":42,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2026,6,15]],"date-time":"2026-06-15T00:00:00Z","timestamp":1781481600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"ANID through the project Fondecyt de Iniciaci\u00f3n en Investigaci\u00f3n 2025","award":["n\u00ba 11250867"],"award-info":[{"award-number":["n\u00ba 11250867"]}]},{"name":"Competition for Research Regular Projects, year 2023","award":["LPR23\u201317"],"award-info":[{"award-number":["LPR23\u201317"]}]},{"name":"Universidad Tecnol\u00f3gica Metropolitana, and the Competition for Scientific and Technological Equipment Projects, year 2024","award":["LE24\u201303"],"award-info":[{"award-number":["LE24\u201303"]}]},{"DOI":"10.13039\/100031750","name":"Universidad de O\u2019Higgins","doi-asserted-by":"crossref","id":[{"id":"10.13039\/100031750","id-type":"DOI","asserted-by":"crossref"}]},{"id":[{"id":"https:\/\/ror.org\/044cse639","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Medical Sciences"],"abstract":"<jats:p>Background: Near-infrared spectroscopy (NIRS)-based wearable devices offer non-invasive, continuous monitoring of muscle oxygenation, providing direct microvascular and metabolic information that complements indirect indices of intensity such as heart rate and accelerometry. Their clinical applicability in chronic non-communicable diseases (NCDs) remains under active development. Methods: A structured narrative review was conducted in PubMed, Scopus, Web of Science, and IEEE Xplore (January 2010\u2013January 2026) using pre-specified search strings combining NIRS, muscle oxygenation, SmO2, StO2, wearable, exercise intensity, ventilatory\/lactate threshold, and individual chronic disease terms. Eligible studies addressed technical validation of wearable NIRS, NIRS-derived exercise intensity estimation, clinical applications in NCDs, or rehabilitation implementation. Evidence was synthesized thematically; quality of validation studies was appraised against AMSTAR-2-informed, COSMIN-informed, or Cochrane RoB-2 criteria. Results: Wearable continuous-wave NIRS shows acceptable concurrent validity with frequency-domain laboratory systems (r = 0.79; range 0.69\u20130.88; \u00b18% SmO2 agreement in 95% of measurements) and good test\u2013retest reliability for moderate-to-severe domains (ICC 0.72\u20130.91). NIRS-derived breakpoints align more reliably with the second ventilatory\/lactate threshold (ICC = 0.80) than with the first (ICC = 0.53), constraining its use for prescribing lower-intensity domains. In chronic obstructive pulmonary disease, peripheral arterial disease, chronic respiratory failure and selected cardiovascular conditions, wearable NIRS detects disease-specific patterns of muscle deoxygenation and post-exercise reoxygenation that track responses to rehabilitation. Conclusions: Current evidence supports wearable NIRS as a complementary, intensity-aware monitoring tool\u2014particularly for delineating the heavy\/severe-intensity boundary and detecting peripheral metabolic limitations\u2014rather than as a stand-alone replacement for ventilatory or lactate thresholds. Because much of the evidence derives from small, single-sex or athlete-only cohorts, these findings should be regarded as a promising basis requiring further validation in broader NCD populations. Implementation in NCDs requires standardized placement and calibration protocols, sex- and body composition-stratified reference values, motion-artifact mitigation, and adequately powered longitudinal trials in clinical populations.<\/jats:p>","DOI":"10.3390\/medsci14020317","type":"journal-article","created":{"date-parts":[[2026,6,15]],"date-time":"2026-06-15T05:59:47Z","timestamp":1781503187000},"page":"317","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["The Effectiveness of NIRS-Based Wearable Devices in Estimating Physical Activity Intensity in Patients with Chronic Non-Communicable Diseases: A Structured Narrative Review"],"prefix":"10.3390","volume":"14","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-0125-485X","authenticated-orcid":false,"given":"Ra\u00fal","family":"Caulier-Cisterna","sequence":"first","affiliation":[{"name":"Department of Informatics and Computing, Facultad de Ingenier\u00eda, Universidad Tecnol\u00f3gica Metropolitana, Santiago 7800002, Chile"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0007-9578-3050","authenticated-orcid":false,"given":"Andr\u00e9s","family":"Vega-Moraga","sequence":"additional","affiliation":[{"name":"Translational Biomedical Laboratory, Facultad de Ingenier\u00eda, Universidad Tecnol\u00f3gica Metropolitana, Santiago 7800002, Chile"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0008-9704-1576","authenticated-orcid":false,"given":"Daniel","family":"Ramos-L\u00f3pez","sequence":"additional","affiliation":[{"name":"Metabolic Rehabilitation Unit, Center of Medical Specialties, Red de Salud UC Christus, Santiago 8330033, Chile"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0674-7506","authenticated-orcid":false,"given":"Felipe","family":"Contreras-Brice\u00f1o","sequence":"additional","affiliation":[{"name":"Instituto de Ciencias de la Salud, Universidad de O\u2019Higgins, Rancagua 2820000, Chile"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,6,15]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Sendra-P\u00e9rez, C., Encarnaci\u00f3n-Mart\u00ednez, A., and Priego-Quesada, J.I. 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