A Zero-Inflated Analysis of Vigorous Physical Activity Among University Students in South Africa

A Zero-Inflated Analysis of Vigorous Physical Activity Among University Students in South Africa | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article A Zero-Inflated Analysis of Vigorous Physical Activity Among University Students in South Africa P. Pitsha, R. T. Chiruka, H. Gomwe, C. S. Marange, L Dlembula This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9496314/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 7 You are reading this latest preprint version Abstract Vigorous physical activity (VPA) is an important health determinant, but participation among university students remains low. When measured as the number of days engaged in VPA, physical activity (PA) data typically exhibit excess zeros and overdispersion, violating the assumptions of the traditional count regression models. This study aimed to identify an appropriate modeling method for analysing VPA count data and to examine factors associated with participation among university students. A cross-sectional study was conducted among 852 students at a South African university. The outcome variable was the number of days of VPA within the past week. Given the distributional characteristics of the data, the NB, ZINB, and HNB models were fitted and compared using AIC and BIC, with the ZINB model providing the best fit. Overdispersion was confirmed using the DHARMa dispersion test; the model diagnostics were further assessed using randomized quantile residuals to validate the results of the best fitting model. The empirical study revealed a large proportion of zero inflation (55.4%) and significant overdispersion. In the count component, living on campus has a higher expected days of VPA compared to students living off campus among the individuals at risk, and diastolic blood pressure were significantly associated with VPA frequency, while gender, specifically males, have 51.89% decrease in the odds of belonging to the not at-risk group. Randomized quantile residuals confirmed adequate model fit. These findings highlight the importance of using flexible count regression models when analysing behavioural health outcomes characterized by excess zeros and overdispersion, ensuring more reliable inference in PA research. Zero-inflation Count data Overdispersion Vigorous physical activity University students Full Text Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Reviews received at journal 16 May, 2026 Reviewers agreed at journal 10 May, 2026 Reviewers invited by journal 05 May, 2026 Editor invited by journal 24 Apr, 2026 Editor assigned by journal 23 Apr, 2026 Submission checks completed at journal 23 Apr, 2026 First submitted to journal 22 Apr, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-9496314","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":637713296,"identity":"96840949-df42-43bd-a66e-1cc559626e63","order_by":0,"name":"P. 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When measured as the number of days engaged in VPA, physical activity (PA) data typically exhibit excess zeros and overdispersion, violating the assumptions of the traditional count regression models. This study aimed to identify an appropriate modeling method for analysing VPA count data and to examine factors associated with participation among university students. A cross-sectional study was conducted among 852 students at a South African university. The outcome variable was the number of days of VPA within the past week. Given the distributional characteristics of the data, the NB, ZINB, and HNB models were fitted and compared using AIC and BIC, with the ZINB model providing the best fit. Overdispersion was confirmed using the DHARMa dispersion test; the model diagnostics were further assessed using randomized quantile residuals to validate the results of the best fitting model. The empirical study revealed a large proportion of zero inflation (55.4\\%) and significant overdispersion. In the count component, living on campus has a higher expected days of VPA compared to students living off campus among the individuals at risk, and diastolic blood pressure were significantly associated with VPA frequency, while gender, specifically males, have 51.89\\% decrease in the odds of belonging to the not at-risk group. Randomized quantile residuals confirmed adequate model fit. These findings highlight the importance of using flexible count regression models when analysing behavioural health outcomes characterized by excess zeros and overdispersion, ensuring more reliable inference in PA research.","manuscriptTitle":"A Zero-Inflated Analysis of Vigorous Physical Activity Among University Students in South Africa","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-05-12 14:46:44","doi":"10.21203/rs.3.rs-9496314/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"editorInvitedReview","content":"","date":"2026-05-16T07:08:54+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"242418077418236684235286544768207711023","date":"2026-05-10T16:30:14+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-05-05T08:38:25+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2026-04-24T05:32:25+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-04-24T03:49:20+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-04-24T03:48:59+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Public Health","date":"2026-04-22T12:15:58+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-public-health","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"pubh","sideBox":"Learn more about [BMC Public Health](http://bmcpublichealth.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/pubh/default.aspx","title":"BMC Public Health","twitterHandle":"@BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"b10b1e66-20fc-415f-b860-bfab5b04096b","owner":[],"postedDate":"May 12th, 2026","published":true,"recentEditorialEvents":[{"type":"editorInvitedReview","content":"","date":"2026-05-16T07:08:54+00:00","index":46,"fulltext":""},{"type":"reviewerAgreed","content":"242418077418236684235286544768207711023","date":"2026-05-10T16:30:14+00:00","index":45,"fulltext":""},{"type":"reviewersInvited","content":"14","date":"2026-05-05T08:38:25+00:00","index":"","fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-05-12T14:46:44+00:00","versionOfRecord":[],"versionCreatedAt":"2026-05-12 14:46:44","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9496314","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9496314","identity":"rs-9496314","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}