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Post-exertional malaise (PEM) is central to case definitions and is usually assessed by patient report. We evaluated the feasibility and clinical value of handgrip strength (HGS) testing in PEM-reporting CYP referred for suspected ME\/CFS.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>In this prospective observational study at the Munich Chronic Fatigue Center for Young People (November 2022\u2013November 2024), 147 patients (10\u201325\u2009years) referred for the assessment of ME\/CFS with positive DSQ-PEM screening and 83 healthy controls (HC) completed two HGS sessions (10 maximal grips\/session; 3-s contraction\/5-s rest; 60-minute inter-session break) using a digital dynamometer. We derived maximal force (Fmax), mean force (Fmean), fatigue ratio (FR\u2009=\u2009Fmax\/Fmean), and recovery ratio (RR\u2009=\u2009Fmean session 2 \/ session 1). Analyses used repeated-measures ANCOVA, linear regression, partial Spearman correlations (adjusted for sex, age, and BMI), and proportional odds models for group membership (HC, noME\/CFS, ME\/CFS), reporting accuracy, and the C-statistic. Sensitivity analyses compared noME\/CFS with confirmed CCC-ME\/CFS.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>\n                      After clinical work-up, 84\/147 (57%) patients were classified as ME\/CFS (confirmed or probable) and 63\/147 (43%) as noME\/CFS. HGS test completion rate was high (session 1: 146\/147, 99.3%; session 2: 142\/147, 96.6%). Compared with HC, patients had substantially lower HGS (mean difference \u22129.93\u2009kg, 95% CI: \u221212.00 to \u22127.85), and HGS indices correlated modestly with physical functioning (SF-12 PCS), but not with PEM duration. Both noME\/CFS and ME\/CFS groups differed from HC in absolute strength indices (Fmean, Fmax) and FR. RR differed between ME\/CFS and HC, whereas no HGS index significantly separated noME\/CFS from ME\/CFS. In proportional odds models, each HGS index improved fit (all\n                      <jats:italic>p<\/jats:italic>\n                      \u2009&lt;\u20090.001), but discrimination across HC, noME\/CFS, and ME\/CFS patients was moderate (accuracy 49.2\u201357.3% vs no-information rate 36.5%, with best performance for Fmean in session 2). In the CCC-restricted sensitivity analysis, discrimination between confirmed CCC-ME\/CFS and noME\/CFS was moderate (accuracy 62.8\u201370.7%; C-statistic 0.63\u20130.73), with best performance for absolute strength indices and RR.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>Standardized two-session repeated HGS testing is feasible in CYP with chronic fatigue and self-reported PEM and provides an objective marker of functional impairment that aligns with physical health status but not with PEM duration. However, HGS alone shows limited ability to discriminate ME\/CFS from other fatiguing noME\/CFS conditions. HGS may be useful for quantitative phenotyping, patient stratification, and longitudinal outcome assessment rather than as a standalone diagnostic biomarker.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Trial registration<\/jats:title>\n                    <jats:p>Not applicable.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1186\/s12967-026-08654-5","type":"journal-article","created":{"date-parts":[[2026,7,15]],"date-time":"2026-07-15T15:53:26Z","timestamp":1784130806000},"update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Handgrip strength in children, adolescents, and young adults with suspected myalgic encephalomyelitis\/chronic fatigue syndrome"],"prefix":"10.1186","volume":"24","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-3835-7964","authenticated-orcid":false,"given":"Lorenz","family":"Mihatsch","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Lisa","family":"Schartner","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Julia Lange","family":"de Luna","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Chiara","family":"H\u00f6hler","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Lara","family":"Bucka","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Lea","family":"Lovrenovic","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sophie","family":"Eidenschink","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Birgit","family":"Schmuck","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Viktoria","family":"Bienemann","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Catharina","family":"Christa","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kirstin","family":"Mittelstra\u00df","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Anna","family":"Hausruckinger","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Cordula","family":"Warlitz","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kaja","family":"Michel","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Katrin","family":"Gerrer","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Helma","family":"Freitag","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Carmen","family":"Scheibenbogen","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Rafael","family":"Pricoco","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Uta","family":"Behrends","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"297","published-online":{"date-parts":[[2026,7,15]]},"reference":[{"key":"8654_CR1","doi-asserted-by":"publisher","first-page":"121","DOI":"10.3389\/fped.2017.00121","volume":"5","author":"PC Rowe","year":"2017","unstructured":"Rowe PC, Underhill RA, Friedman KJ, Gurwitt A, Medow MS, Schwartz MS, et al. 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