{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,5]],"date-time":"2026-10-05T04:52:42Z","timestamp":1791175962511,"version":"4.1.0"},"reference-count":39,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,10,5]],"date-time":"2026-10-05T00:00:00Z","timestamp":1791158400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Public Health"],"abstract":"\n Introduction<\/jats:title>\n Studies of COVID-19 and physical fitness in Chinese university students rarely extend beyond 2022, and none has formally tested whether post-pandemic trends differ by sex.<\/jats:p>\n <\/jats:sec>\n \n Methods<\/jats:title>\n \n Using 21\u202fyears of routinely collected fitness data (2005\u20132025), we examined indicator-specific change and sex differences in population-level trends in a repeated cross-sectional design. The cardiorespiratory analytic sample comprised 297,565 valid records from 91,686 full-time undergraduates at one comprehensive university in Zhejiang Province, China. Six indicators were classified by data availability and suitability for interrupted time series (ITS) analysis; cardiorespiratory endurance (1000-m run for men, 800-m for women) was pre-specified as the primary outcome and body weight was analysed within the same framework as a negative control. The unit of analysis was the annual grade-standardised mean, giving 18 time points per sex. Single-breakpoint models estimated the immediate level change at 2020 (\n \u03b2<\/jats:italic>\n 2<\/jats:sub>\n ) and the change in annual trend thereafter (\n \u03b2<\/jats:italic>\n 3<\/jats:sub>\n ); a sex \u00d7 trend interaction tested whether post-2020 trends differed between women and men; Benjamini\u2013Hochberg correction was applied across five confirmatory tests.\n <\/jats:p>\n <\/jats:sec>\n \n Results<\/jats:title>\n \n Run times in 2020 rose above counterfactual projections in both sexes (women +9.60\u202fs, 95% CI 2.58\u201316.62,\n p<\/jats:italic>\n \u202f=\u202f0.011,\n q<\/jats:italic>\n \u202f=\u202f0.019; men +13.02\u202fs, 95% CI 4.76\u201321.28,\n p<\/jats:italic>\n \u202f=\u202f0.005,\n q<\/jats:italic>\n \u202f=\u202f0.019), although this immediate change was attenuated and no longer significant when fourth-year students, tested in May 2020 rather than December, were excluded. Post-2020 trends differed by sex (interaction\n p<\/jats:italic>\n \u202f=\u202f0.030,\n q<\/jats:italic>\n \u202f=\u202f0.037) and this difference was robust to that exclusion. In men the post-2020 trend did not differ significantly from the pre-pandemic trend (\n \u03b2<\/jats:italic>\n 3<\/jats:sub>\n \u202f=\u202f\u22120.47\u202fs\/year,\n p<\/jats:italic>\n \u202f=\u202f0.609), with the 2025 annual mean remaining about 14.9\u202fs above the counterfactual projection. In women the trend was significantly steeper (\n \u03b2<\/jats:italic>\n 3<\/jats:sub>\n \u202f=\u202f+2.25\u202fs\/year,\n p<\/jats:italic>\n \u202f=\u202f0.011,\n q<\/jats:italic>\n \u202f=\u202f0.019), widening the gap to about 26.0\u202fs by 2025. Body weight rose steadily across the whole period but showed no change attributable to the pandemic (level change\n p<\/jats:italic>\n \u202f=\u202f0.31 and 0.70; trend change\n p<\/jats:italic>\n \u202f=\u202f0.57 and 0.92 in women and men), which is consistent with the cardiorespiratory result reflecting something other than an artefact of the model.\n <\/jats:p>\n <\/jats:sec>\n \n Discussion<\/jats:title>\n Cardiorespiratory endurance was the only indicator analysed by ITS that showed a sustained pandemic-associated change, and its subsequent trend diverged by sex. These are aggregate population trends rather than individual trajectories, but they suggest that post-pandemic aerobic programming may need to be sex-specific, and that continuity of aerobic activity deserves explicit attention in emergency preparedness planning.<\/jats:p>\n <\/jats:sec>","DOI":"10.3389\/fpubh.2026.1910319","type":"journal-article","created":{"date-parts":[[2026,10,5]],"date-time":"2026-10-05T04:33:10Z","timestamp":1791174790000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Sex-divergent trends in cardiorespiratory endurance after the COVID-19 pandemic: a 21-year interrupted time series analysis of Chinese university students"],"prefix":"10.3389","volume":"14","author":[{"given":"Chao","family":"Song","sequence":"first","affiliation":[{"name":"Department of Psychology, Zhejiang Sci-Tech University","place":["Hangzhou, Zhejiang, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Xinkui","family":"Hu","sequence":"additional","affiliation":[{"name":"Department of Psychology, Zhejiang Sci-Tech University","place":["Hangzhou, Zhejiang, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ningyan","family":"Lu","sequence":"additional","affiliation":[{"name":"Department of Psychology, Zhejiang Sci-Tech University","place":["Hangzhou, Zhejiang, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Wei","family":"Gao","sequence":"additional","affiliation":[{"name":"Department of Psychology, Zhejiang Sci-Tech University","place":["Hangzhou, Zhejiang, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Feng","family":"Xie","sequence":"additional","affiliation":[{"name":"Department of Physical Education, Zhejiang Sci-Tech University","place":["Hangzhou, Zhejiang, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yanqiang","family":"Yin","sequence":"additional","affiliation":[{"name":"Department of Physical Education, Zhejiang Sci-Tech University","place":["Hangzhou, Zhejiang, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Linlin","family":"Yan","sequence":"additional","affiliation":[{"name":"Department of Psychology, Zhejiang Sci-Tech University","place":["Hangzhou, Zhejiang, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Duming","family":"Wang","sequence":"additional","affiliation":[{"name":"Department of Psychology, Zhejiang Sci-Tech University","place":["Hangzhou, Zhejiang, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Zhe","family":"Wang","sequence":"additional","affiliation":[{"name":"Department of Psychology, Zhejiang Sci-Tech University","place":["Hangzhou, Zhejiang, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Guomin","family":"Li","sequence":"additional","affiliation":[{"name":"Department of Physical Education, Zhejiang Sci-Tech University","place":["Hangzhou, Zhejiang, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2026,10,5]]},"reference":[{"key":"ref1","doi-asserted-by":"publisher","first-page":"886","DOI":"10.1001\/jamapediatrics.2022.2313","article-title":"Global changes in child and adolescent physical activity during the COVID-19 pandemic: a systematic review and meta-analysis","volume":"176","author":"Neville","year":"2022","journal-title":"JAMA Pediatr"},{"key":"ref2","doi-asserted-by":"publisher","first-page":"101959","DOI":"10.1016\/j.pmedr.2022.101959","article-title":"Youth physical activity and the COVID-19 pandemic: a systematic review","volume":"29","author":"Do","year":"2022","journal-title":"Prev Med 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