Replicability and transparency in physical therapy research: Time to wake up

Replicability and transparency in physical therapy research: Time to wake up | medRxiv /* */ /* */ <!-- <!-- /*! * yepnope1.5.4 * (c) WTFPL, GPLv2 */ (function(a,b,c){function d(a){return"[object Function]"==o.call(a)}function e(a){return"string"==typeof a}function f(){}function g(a){return!a||"loaded"==a||"complete"==a||"uninitialized"==a}function h(){var a=p.shift();q=1,a?a.t?m(function(){("c"==a.t?B.injectCss:B.injectJs)(a.s,0,a.a,a.x,a.e,1)},0):(a(),h()):q=0}function i(a,c,d,e,f,i,j){function k(b){if(!o&&g(l.readyState)&&(u.r=o=1,!q&&h(),l.onload=l.onreadystatechange=null,b)){"img"!=a&&m(function(){t.removeChild(l)},50);for(var d in y[c])y[c].hasOwnProperty(d)&&y[c][d].onload()}}var j=j||B.errorTimeout,l=b.createElement(a),o=0,r=0,u={t:d,s:c,e:f,a:i,x:j};1===y[c]&&(r=1,y[c]=[]),"object"==a?l.data=c:(l.src=c,l.type=a),l.width=l.height="0",l.onerror=l.onload=l.onreadystatechange=function(){k.call(this,r)},p.splice(e,0,u),"img"!=a&&(r||2===y[c]?(t.insertBefore(l,s?null:n),m(k,j)):y[c].push(l))}function j(a,b,c,d,f){return q=0,b=b||"j",e(a)?i("c"==b?v:u,a,b,this.i++,c,d,f):(p.splice(this.i++,0,a),1==p.length&&h()),this}function k(){var a=B;return a.loader={load:j,i:0},a}var l=b.documentElement,m=a.setTimeout,n=b.getElementsByTagName("script")[0],o={}.toString,p=[],q=0,r="MozAppearance"in l.style,s=r&&!!b.createRange().compareNode,t=s?l:n.parentNode,l=a.opera&&"[object Opera]"==o.call(a.opera),l=!!b.attachEvent&&!l,u=r?"object":l?"script":"img",v=l?"script":u,w=Array.isArray||function(a){return"[object Array]"==o.call(a)},x=[],y={},z={timeout:function(a,b){return b.length&&(a.timeout=b[0]),a}},A,B;B=function(a){function b(a){var a=a.split("!"),b=x.length,c=a.pop(),d=a.length,c={url:c,origUrl:c,prefixes:a},e,f,g;for(f=0;f<d;f++)g=a[f].split("="),(e=z[g.shift()])&&(c=e(c,g));for(f=0;f<b;f++)c=x[f](c);return c}function g(a,e,f,g,h){var i=b(a),j=i.autoCallback;i.url.split(".").pop().split("?").shift(),i.bypass||(e&&(e=d(e)?e:e[a]||e[g]||e[a.split("/").pop().split("?")[0]]),i.instead?i.instead(a,e,f,g,h):(y[i.url]?i.noexec=!0:y[i.url]=1,f.load(i.url,i.forceCSS||!i.forceJS&&"css"==i.url.split(".").pop().split("?").shift()?"c":c,i.noexec,i.attrs,i.timeout),(d(e)||d(j))&&f.load(function(){k(),e&&e(i.origUrl,h,g),j&&j(i.origUrl,h,g),y[i.url]=2})))}function h(a,b){function c(a,c){if(a){if(e(a))c||(j=function(){var a=[].slice.call(arguments);k.apply(this,a),l()}),g(a,j,b,0,h);else if(Object(a)===a)for(n in m=function(){var b=0,c;for(c in a)a.hasOwnProperty(c)&&b++;return b}(),a)a.hasOwnProperty(n)&&(!c&&!--m&&(d(j)?j=function(){var a=[].slice.call(arguments);k.apply(this,a),l()}:j[n]=function(a){return function(){var b=[].slice.call(arguments);a&&a.apply(this,b),l()}}(k[n])),g(a[n],j,b,n,h))}else!c&&l()}var h=!!a.test,i=a.load||a.both,j=a.callback||f,k=j,l=a.complete||f,m,n;c(h?a.yep:a.nope,!!i),i&&c(i)}var i,j,l=this.yepnope.loader;if(e(a))g(a,0,l,0);else if(w(a))for(i=0;i (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];var j=d.createElement(s);var dl=l!='dataLayer'?'&l='+l:'';j.src='//www.googletagmanager.com/gtm.js?id='+i+dl;j.type='text/javascript';j.async=true;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-P4HH5NV'); Skip to main content Home About Submit ALERTS / RSS Search for this keyword Advanced Search Replicability and transparency in physical therapy research: Time to wake up View ORCID Profile François Jabouille , View ORCID Profile Ata Farajzadeh , Adèle Guillemot Exertier , Jérôme Martine , Natalie Sadek , Leonardo Huet Klinger , Coman Matthew Iliut , Valérie Kapsa , View ORCID Profile Matthieu P. Boisgontier doi: https://doi.org/10.1101/2025.09.23.25336497 François Jabouille 1 School of Rehabilitation Sciences, Faculty of Health Sciences, University of Ottawa , Ottawa, Canada Find this author on Google Scholar Find this author on PubMed Search for this author on this site ORCID record for François Jabouille Ata Farajzadeh 1 School of Rehabilitation Sciences, Faculty of Health Sciences, University of Ottawa , Ottawa, Canada Find this author on Google Scholar Find this author on PubMed Search for this author on this site ORCID record for Ata Farajzadeh Adèle Guillemot Exertier 1 School of Rehabilitation Sciences, Faculty of Health Sciences, University of Ottawa , Ottawa, Canada Find this author on Google Scholar Find this author on PubMed Search for this author on this site Jérôme Martine 1 School of Rehabilitation Sciences, Faculty of Health Sciences, University of Ottawa , Ottawa, Canada Find this author on Google Scholar Find this author on PubMed Search for this author on this site Natalie Sadek 1 School of Rehabilitation Sciences, Faculty of Health Sciences, University of Ottawa , Ottawa, Canada Find this author on Google Scholar Find this author on PubMed Search for this author on this site Leonardo Huet Klinger 1 School of Rehabilitation Sciences, Faculty of Health Sciences, University of Ottawa , Ottawa, Canada Find this author on Google Scholar Find this author on PubMed Search for this author on this site Coman Matthew Iliut 1 School of Rehabilitation Sciences, Faculty of Health Sciences, University of Ottawa , Ottawa, Canada Find this author on Google Scholar Find this author on PubMed Search for this author on this site Valérie Kapsa 1 School of Rehabilitation Sciences, Faculty of Health Sciences, University of Ottawa , Ottawa, Canada Find this author on Google Scholar Find this author on PubMed Search for this author on this site Matthieu P. Boisgontier 1 School of Rehabilitation Sciences, Faculty of Health Sciences, University of Ottawa , Ottawa, Canada 2 Institut du Savoir Monfort, Hôpital Monfort , Ottawa, Canada 3 Bruyère Research Institute , Ottawa, Canada Find this author on Google Scholar Find this author on PubMed Search for this author on this site ORCID record for Matthieu P. Boisgontier For correspondence: matthieu.boisgontier{at}uottawa.ca Abstract Full Text Info/History Metrics Data/Code Preview PDF ABSTRACT Background Over the past decade, a replication crisis has been recognized in several scientific disciplines, raising concerns about the validity and reliability of published research and eroding scientific credibility. While this crisis has been widely discussed in other fields, its impact on physical therapy research has received little attention. Objective This study aimed to provide an overview of the current state of physical therapy research practices that could suggest low replicability. Methods We assessed the research practices in all original research articles published in official journals of national physical therapy associations in the USA (Physical Therapy), Canada (Physiotherapy Canada), the UK (Physiotherapy), and Australia (Journal of Physiotherapy) between 2022 and 2024. Results A total of 465 original research articles were identified. Of these, 28% were preregistered, 0% were replication studies or registered reports, and 12% provided open data. Sample size justification was reported in 37% of quantitative studies and 23% of qualitative studies. Despite an average time from submission to publication of 400 days, only 1% of manuscripts were preprinted. Among quantitative studies, 33% stated a hypothesis, while 63% relied on significance testing. Of the reported significant p -values, 39% fell within the fragile range (.01≤ p<.05), substantially exceeding the expected 26% under 80% power and suggesting questionable research practices. Hypotheses were supported in 83% of cases, indicating an unreasonably high rate of positive results. A marked difference in the number of p -values just above and just below the significance threshold suggested publication bias. Conclusion These results suggest shortcomings in the reproducibility, replicability, and transparency of the physical therapy literature. Addressing these issues requires the adoption of best practices, including registered reports, justifying sample sizes, publishing negative results, and sharing data and code. Delays in implementing these practices risk exacerbating bias in the literature and undermining the scientific credibility of physical therapy research. Statement This manuscript is a preprint and is not peer-reviewed. All authors have approved this version of the manuscript. Citation Jabouille F, Farajzadeh A, Guillemot Exertier A, Martine J, Sadek N, Huet Klinger L, Iliut CM, Kapsa V, & Boisgontier MP. Replicability and transparency in physical therapy research: Time to wake up. MedRxiv . 2025. INTRODUCTION In 2011, 270 researchers from 18 countries and 125 institutions began collaborating to replicate 100 studies to test the reliability of prior finding in psychology with different data ( Open Science Collaboration, 2015 ; Nosek et al., 2022 ). While 97% of the original studies reported statistically significant results, only 36% of the replications did so. Moreover, the effect sizes of the successful replications were often smaller than the original reports ( Open Science Collaboration, 2015 ). Similar replication issues have been reported in other fields, including pharmacology (21%) ( Prinz et al., 2011 ), neuroscience (6%) ( Boekel et al., 2015 ), cancer biology (40%) ( Errington et al., 2021 ), and exercise science (28%) ( Murphy et al., 2025 ). This poor replicability is often attributed to researcher degrees of freedom ( Simmons et al., 2011 ), which provide scholars with the flexibility to modify hypotheses, study design, data analysis, statistical analysis, and reporting after the results are known ( Büttner et al., 2020 ). If these decisions are not preregistered or made transparent, they create opportunities for questionable research practices, whether deliberate or unintentional, that increase the risk of biased and unreplicable results ( John et al., 2012 ; Boekel et al., 2015 ; Boisgontier, 2022 ). Common examples include selectively reporting experiments or variables that produce a desired result (“cherry picking”), presenting unexpected results as if they had been hypothesized a priori (“HARKing”), and conducting various forms of p -hacking until statistical significance is achieved ( Büttner et al., 2020 ). Researchers may engage in these practices for various reasons ( Wiggins & Christopherson, 2019 ). At the system level, these include incentive structures in academia that privilege positive findings ( Allen & Mehler, 2019 ) and the pressures of a “publish-or-perish” culture ( Moosa, 2024 ). At the individual level, contributing factors include cognitive biases, such as the desire to be right ( Nickerson, 1998 ), and the ambition to gain rapid recognition through striking results, even at the expense of methodological rigor ( Maltby et al., 2008 ). These questionable research practices not only increase the risk of unreplicable results but also contribute to unrealistically high rates of positive results: 88% in applied sciences ( Fanelli, 2010 ), 82% in sports medicine ( Büttner et al., 2020 ), and 81% in exercise sciences ( Twomey et al., 2021 ). Physical therapy is an applied science and shares similar research training practices and academic incentives with sports medicine and exercise sciences. It is therefore urgent to examine whether physical therapy research also exhibit inflated positive result rates, which may signal broader systemic issues in research transparency and methods. In response to poor replicability, questionable research practices, and unrealistic positive results rates, several fields have recommended the adoption of protocol registration and other open science practices. While these measures have strengthened the literature in psychology ( Bogdan, 2025 ; Bakker et al., 2025 ), their adoption remains limited in disciplines closely related to physical therapy, such as sports medicine ( Bullock et al., 2023 ), and has not yet been systematically examined in physical therapy research. The objective of this study was to assess the current state of physical therapy literature and reporting practices by examining key indicators, including the proportion of positive results, replication studies, pre-registrations, registered reports, sample size justification, open data, effect size reporting, fragile p -values, p -value distribution, and preprinting. METHODS Sample A systematic search was conducted to identify the articles reporting original research that were published from 2022 to 2024 in the flagship journals of the leading physical therapy associations in the United States (American Physical Therapy Association), Canada (Canadian Physiotherapy Association), the United Kingdom (Chartered Society of Physiotherapy), and Australia (Australian Physiotherapy Association). These journals provide a sample of the current state of research practices of physiotherapy worldwide. They are, respectively, PTJ: Physical Therapy & Rehabilitation Journal ( https://academic.oup.com/ptj ), Physiotherapy Canada ( https://www.utpjournals.press/loi/ptc ), Physiotherapy ( https://www.csp.org.uk/professional-clinical/clinical-evidence/physiotherapy-journal ), and Journal of Physiotherapy ( https://www.sciencedirect.com/journal/journal-of-physiotherapy ). Only original studies were included in the analyses. Data Extraction Nine coders (FJ, AF, AGE, JM, NS, LHK, CMI, VK) were responsible for data extraction. All coders received standardized training informed by previous research ( Twomey et al., 2021 , Buttner et al., 2020; Scheel et al., 2021 ). Each article was independently coded by at least two coders, and any conflicts were resolved by one of the co-first authors (FJ, AF). Data were extracted across seven domains: research topic, data sharing, replication, preregistration, registered report, sample size justification, support for hypotheses, statistical reporting, and preprint. Research Topics All journal articles were categorized into 20 research topics: acute care, balance and falls, cardiovascular and pulmonary, covid, diabetes, education, geriatrics, health policy, implementation science, knowledge translation, measurement, musculoskeletal, neurology, oncology, pain management, pediatrics, prevention and health promotion, professional issues, psychosocial, and women’s health. Replication Replication refers to testing the reliability of a prior finding with different data ( Nosek et al., 2022 ). To identify replication studies, the articles were searched for the string ‘replic * ‘ ( Scheel et al., 2021 ). Preregistration Preregistration is the practice of making a publicly accessible, time-stamped record of a research plan prior to data collection ( Nosek et al., 2018 ). To assess preregistration, we searched for statements or links indicating that the study had been preregistered. Registered Report A registered report is a publication format with the following submission timeline: Before data collection, authors submit a study protocol outlining their hypotheses, planned methods, and analysis plans. This protocol undergoes peer review. If the protocol is approved, the journal grants in-principle acceptance, committing to publish the final article regardless of whether the hypotheses are supported. Then, authors collect and analyze the data and complete the final report. A second round of peer review then verifies adherence to the registered protocol, ensures that the conclusions are justified, and confirms that the data meet any prespecified quality checks. To assess whether authors could publish registered reports, we examined the websites of the sampled journals to determine whether they offered this type of article. Sample Size Justification To examine sample size justifications, we distinguished between qualitative and quantitative studies, as the two approaches rely on different types of justification. This distinction was made based on an explicit mention of a qualitative methodology in the methods section. For qualitative studies, sample size justifications were classified into four categories ( Vasileiou et al., 2018 ): (1) data saturation, whereby data collection continues until no new themes emerge; (2) information power, whereby more informative data per participant requires a smaller sample size; (3) data adequacy, reflecting the richness and volume of data; and (4) heuristic, based on generally accepted rules of thumb or norms. For quantitative studies, justifications were grouped into (1) a priori power analysis, (2) accuracy (i.e., precision of parameter estimates), (3) heuristic, and (4) resource constraints (e.g. limitations due to time, funding, or participant availability) ( Lakens, 2022b ). For a priori power analyses (1), justifications for the smallest effect size of interest were categorised as benchmark, pilot study, previous study, or meta-analysis ( Lakens et al., 2018 ). Hypothesis Statement & Support To assess the proportion of results that supported the tested hypotheses (i.e., positive results), we first identified articles that stated an explicit hypothesis. If so, we then determined whether the hypothesis was fully supported, partially supported, or not supported, based on the authors’ description of the results. When multiple hypotheses were tested, the primary hypothesis was considered to be the first hypothesis mentioned in the text, unless otherwise clarified ( Fanelli, 2010 ; Scheel et al., 2021 ). Statistical Reporting To assess the use of null hypothesis significance testing, we searched for related statements and the reporting of p -values. We coded whether p -values were interpreted as significant and classified their reporting as exact (e.g., p = 0.04), relative (e.g., p < 0.05), or mixed. A report of p < 0.001 was treated as exact, as some statistical software programs do not provide p -values below this threshold ( Twomey et al., 2021 ). We also extracted whether effect sizes were reported, including Cohen’s d , correlation coefficients, mean differences, and measures of model fit ( Twomey et al., 2021 ). Fragile P -Values Questionable research practices could be inferred by the proportion of fragile p -values, which refers to a result that could easily change from statistically significant to non-significant with only a small change in the data ( Walsh et al., 2014 ). To extract p -values, the unformatted “Results” sections of articles reporting significance tests were extracted, excluding captions, tables, and figures, using code adapted from Bogdan (2025) . After p -value extraction, the proportion of fragile significant p -values was calculated for each article as the number of p-values between.01 and.05 (.01 ≤ p <.05) divided by the number of p values strictly below.05. Only p - values reported with equal (=) or less than (< or ≤) signs were included, with ≤ treated as <. For studies that reported all significant p -values as “p <.05”, a correction was applied: fragile p -value percentages were recomputed based on nearby test statistics when available. If no test statistics were reported, the fragile p-value percentage was set to 51% ( Bogdan, 2025 ). P -Value Distribution To assess publication bias, which describes publishing behaviors that give manuscripts that find support for their tested hypotheses a higher chance of being published than manuscripts with “negative” results (Franco et al., 2014; Scheel et al., 2021 ), we examined the distribution of p - values on each side of the significance threshold. First, all extracted exact p -values (reported with “=“) were transformed into z-values to facilitate interpretation and plotted to visualize potential differences just above versus just below the significance threshold ( Kühberger et al., 2014 ). Second, relative p -values (reported with ““) were categorized into two groups: p .05. Data Sharing Reproducibility refers to testing the reliability of a prior finding using the same data and the same analysis strategy ( Nosek et al., 2022 ). The most basic requirement for reproducibility is accessible data. To assess data accessibility, we searched for a data availability statement. If a statement was present, we examined whether the dataset was openly accessible, either via a direct link or as a supplementary file. Preprints A preprint is a complete version of a manuscript that authors upload to a public server before peer review ( Berg et al., 2016 ; ASAPbio, 2023 ). To determine whether an article had been preprinted, we first searched for a corresponding statement. If no such statement was present, we searched Google Scholar using the article title. To estimate the potential for acceleration of knowledge dissemination through preprinting, we calculated the number of days between the journal submission date and the publication of the article online. RESULTS Types of Articles Between 2022 and 2024, the four journals published a total of 1,173 articles: 590 in PTJ (American Physical Therapy Association), 168 in Physiotherapy Canada (Canadian Physiotherapy Association), 150 in Physiotherapy (UK Chartered Society of Physiotherapy), and 265 in the Journal of Physiotherapy (Australian Physiotherapy Association). Of these articles, 465 (40%) were original research studies, comprising 391 (84%) quantitative studies and 74 (16%) qualitative studies. The other types of articles included review (14%), perspectives (10%), commentaries (10%), letters to the editor (6%), synopsis (6%), editorials (5%), news (3%), correction (2%), protocols (2%), case reports (2%), guidelines (1%), and historical essays, announcements and association business (<1%) ( Figure 1 ). Among the reviews, 27% were narrative reviews, 72% were systematic reviews, and 43% included a meta-analysis. One study was a meta-analysis of individual patient data without a systematic review. Download figure Open in new tab Figure 1. Published articles by type from 2022 to 2024 Sample Size and Sex Distribution by Research Topic The median sample size varied considerably by research topic, ranging from 31 participants in the field of neurology to 4,652 in the field of health policy ( Table 1 ). On average, female participants represented 61% (n = 496,294) of the total number of participants in the sampled studies. The proportion of female participants exceeded 70% in studies on diabetes, geriatrics, professional issues, and psychosocial research. In contrast, the proportion of male participants exceeded 55% in cardiovascular and pulmonary research only ( Table 1 ). View this table: View inline View popup Download powerpoint Table 1. Sample size and sex distribution by research topic Replications None of the 465 original articles were replication studies ( Figure 2A ). Download figure Open in new tab Figure 2. Research practices in physical therapy. (A) Research practices. (B) Quantitative research practices. (C) Types and frequencies of hypothesis support. (D) Sample size justification by type of hypothesis support. (E) Types of power analysis justification. (F) Proportion of fragile p -values per article (shaded area represents ± 1 standard error). (G) Distribution of z-transformed exact p -value (dashed line represents the z-statistic (1.96) associated with p =.05 significance). (H) Distribution of relative p -values. Preregistrations Preregistration statements were present in 28% of the articles ( Figure 2A ). Registries included the Australian New Zealand Clinical Trials Registry (ANZCTR), Brazilian Registry of Clinical Trial (ReBec), Chinese Clinical Trial Registry (ChiCTR), Clinical trials, Clinical Trials Registry India (CTRI), Netherlands Trial Register (LTR), Open Science Framework OSF), International Clinical Trials Registry Platform (ICTRP), Comet Initiative, International Standard Randomised Controlled Trial Number (ISRCTN), and the Pan-African Clinical Trials Registry (PACTR). Registered Reports None of the sampled journals offered the registered report format for publication. Consequently, the proportion of registered reports was 0% ( Figure 2A ). Sample Size Justification Sample size justification was reported in 37% of the quantitative articles ( Figure 2B ) and 23% of the qualitative articles. Among the 37% of quantitative studies justifying their sample size, the most common justification was an a priori power analysis (69%), followed by heuristic (23%), accuracy (6%), and resource constraints (2%). Of those using an a priori power analysis, 47% relied on previous studies to determine the smallest effect size of interest, 35% on benchmark values, 18% on pilot data, and 0% on meta-analyses ( Figure 2E ). Articles fully supporting their hypothesis justified their sample size in 38% of cases, whereas articles reporting partial or no support both did so 59% of cases ( Figure 2D ). For qualitative studies, justifications included information power (29%), data saturation (29%), heuristic (24%), and data adequacy (18%). Hypothesis Statement and Support Among the 391 quantitative studies, 130 (33%) explicitly stated at least one hypothesis ( Figure 2B ). Of these, 83% supported the main hypothesis ( Figure 2B ): 53% reported full support, 30% partial support, and 17% no support ( Figure 2C ). Excluding knowledge translation and diabetes due to an insufficient sample size (k = 2), the prevalence of hypothesis testing ranged from 8% in implementation science to 71% in geriatrics ( Figure 3A ). Hypothesis support varied by topic, ranging from 0% support in psychosocial studies to 100% support in prevention and health promotion, pediatrics, implementation science, education, COVID, and acute care ( Figure 3B ). Download figure Open in new tab Figure 3. Hypothesis statement (A) and support (B) by research topic Statistical Reporting Statistical reporting practices were assessed in quantitative original articles only (k = 391). Although 33% of quantitative studies stated a hypothesis, 63% used some form of significance testing ( Figure 2B ). Notably, 52% of studies without a stated hypothesis still applied significance testing. Among studies using significance testing, 47% reported exact p -values, 9% reported relative p -values, and 44% reported a combination of both. In addition, 81% of studies reported at least one effect size to contextualize their findings ( Figure 2B ). Fragile P -Values Assuming 80% statistical power, the expected percentage of fragile p -values is 26% ( Bogdan, 2025 ). Among the 391 quantitative studies, 204 reported p -values in their results section. 39.4% of the significant p -values were in the fragile range, with yearly rates of 38.1% in 2022, 39.1% in 2023, and 41.1% in 2024 ( Figure 2F ). These rates substantially exceed the expected 26%, suggesting that significant findings in the field are more fragile than would be anticipated under adequately powered conditions, which may reflect the influence of questionable research practices. Distribution of P -Values The distribution of exact p -values showed a drop around the critical z-score of 1.96 (p =.05), with frequencies dropping from 170 in the bin just above to 65 in the bin just below ( Figure 2G ). The resulting ratio of p -values just reaching significance to those just failing is 2.6:1, an outcome that is a highly unlikely under normal conditions. Further, among relative p -values, 861 fell in the p .05 category ( Figure 2H ). Together, these results suggest the presence of publication bias. Data Sharing Although 36% of the articles included a data accessibility statement, only 12% made their data openly available ( Figure 2A ). The remaining 24% were “available upon reasonable request”. Preprints & Time to Publication Six manuscripts (1.3%) were available as preprints ( Figure 2A ). The average time from submission of a manuscript to publication in a journal was 400 ± 199 days. DISCUSSION Main Findings To assess the current state of research and reporting practices, we systematically evaluated 465 original articles published between 2022 and 2024 in the flagship journals of the leading physical therapy associations in the United States, Canada, the United Kingdom, and Australia. We observed that 83% of the studies confirmed their main hypothesis, which is a highly unlikely positive result rate. Only 37% of the quantitative studies and 23% of the qualitative studies justified their sample size, which increases the risk of low-powered studies. No registered reports or replication studies were conducted, and pre-registration was low (28%), paving the way for post-hoc questionable research practices. Data were openly available in only 12% of articles, which limits reproducibility. The mean proportion of fragile p -values per article was 39%, exceeding the expected percentage of 26% and suggesting questionable research practices. An inordinately high number of p-values just passed the boundary of significance, suggesting publication bias. Only six articles were preprinted, delaying the dissemination of research results. Unrealistically High Rate of Hypothesis Support The positive result rate of 83% that we identified in the physical therapy literature was comparable to the rates reported in sports medicine (82%) ( Büttner et al., 2020 ), exercise sciences (81%) ( Twomey et al., 2021 ), and applied sciences (88%) ( Fanelli, 2010 ). This extremely high rate of hypothesis support may be partly explained by questionable research practices, which have been consistently admitted by scientists in several fields ( John et al., 2012 ; Fiedler & Schwarz, 2016 ; Agnoli et al., 2017 ; Fraser et al., 2018 ; Makel et al., 2021 ; Gopalakrishna et al., 2022 ; Isbell et al., 2022 ; Schneider et al., 2024 ). Another possible explanation is publication bias, which can be indirectly evidenced by the analysing p -value distributions ( Kühberger et al., 2014 ; Borg et al., 2023 ). In our study, these distributions clearly suggested the presence of publication bias. To reduce this bias and the incentive to publish positive results only, physical therapy journals could explicitly state that they accept negative results and dedicate a section to these studies, similar to what other journals have implemented ( PLoS One, 2025 ). Limited Use of Registration Practices Another way to reduce this publication bias and to reduce the possibility for questionable research practices is to encourage authors to register their research plans prior to data collection through preregistration ( Kaplan & Irvin, 2015 ; Zarin et al., 2019 ) or registered reports ( Allen & Mehler, 2019 ; Scheel et al., 2021 ). These practices aim to prevent the methods from being influenced by the observed data ( Lakens et al., 2024 ). The value of registered reports is clearly demonstrated in psychology, where 96% of standard reports yielded positive results ( Scheel et al., 2021 ). In contrast, when the nature of the results became irrelevant to acceptance for publication through the registered report format, the proportion of positive results dropped to 44%, which more closely reflects the proportion of true effects one would expect in reality ( Scheel et al., 2021 ). None of the journals of the leading physical therapy associations we included in this study offered researchers the option of submitting their work as a registered report, and the rate of preregistration was slightly above one quarter of the articles (28%). This rate is similar to those reported for clinical trials (26%) ( Bramley et al., 2025 ) and higher than in the fields of exercise sciences (9%) ( Twomey et al., 2021 ) or psychology (3%) ( Hardwicke et al., 2022 ). To reduce publication bias and the opportunities for questionable research practices, journals should offer registered reports as an article type, enabling authors to obtain in-principle acceptance based on their peer-reviewed protocol. Journals could also partner with platforms that conduct independent peer reviews of registered reports (e.g., Peer Community In Registered Reports: https://rr.peercommunityin.org/PCIRegisteredReports/about/about ). Replicability: A Blind Spot and a Crisis to Come The high rate of positive findings reported here calls into question the replicability of physical therapy research. Yet, this replicability is not assessed. We found no replication studies in the sampled journals over a 3-year period. However, replicability can be studied indirectly by examining the distribution of p -values ( Bogdan, 2025 ). For example, studies with 80% statistical power should show fewer than 26% of p -values within the.01 ≤ p ≤.05 interval ( Bogdan, 2025 ). Here, on average, 39% of the p-values per article were fragile. This percentage is higher than that experienced by psychology more than a decade ago (32%) between 2004 and 2011, before their replicability crisis ( Bogdan, 2025 ). Since then, the robustness of psychology research has gradually increased, with the percentage of fragile p -values nearly reaching 26% ( Bogdan, 2025 ). Our results suggest that the proportion of replicable studies in physical therapy may be comparable to or lower than the 36% rate observed in psychology before its replicability crisis ( Open Science Collaboration, 2015 ). Risk of False Findings Sample size is critical for reproducibility because it directly affects the risk of obtaining false results ( Brysbaert, 2019 ). Justifying the sample size enables readers to evaluate this risk and determine whether it is acceptable given the knowledge contributed by the study. However, in the four journals we analyzed, only 37% of articles provided a justification for their sample size. Consequently, in approximately two thirds of the articles, readers cannot determine whether the sample size was adequate to reliably detect the tested effects, nor whether the decision not to assess this risk was reasonable. Moreover, the accuracy of a power analysis depends on the reliability of the effect size used. Yet, none of the studies relied on the strongest form of justification (i.e., meta-analytic estimates), and 35% relied on conventional benchmarks rather than empirical evidence, an approach that is widely discouraged as it offers no study-specific rationale ( Lakens, 2022b ). To address this issue, physical therapy journals should explicitly encourage authors to justify their sample size and to provide sufficient information to enable their a priori power analyses to be reproduced ( Mckay et al., 2023 ). Low Reproducibility Only 12% of articles made their data directly available in a public repository or as supplementary material, meaning that reproducibility could be directly assessed in just over one-tenth of the physical therapy literature. An additional 24% of articles included a data availability statement indicating that datasets were available upon reasonable request. However, such statements have proven largely ineffective: in a study of 3,556 BioMed Central articles, 93% of authors who made these statements either did not respond or declined to share their data ( Gabelica et al., 2022 ). To improve reproducibility in physical therapy research, journals could adopt a default open data policy, permitting exceptions only when authors provide documented evidence that data sharing is restricted by an ethics boards or third-party agreements. Evidence from the social sciences suggests that such policies would be well received, with 88% of authors expressing support for the posting of data or code online ( Ferguson et al., 2023 ). Moreover, established journals such as the British Medical Journal already require data and code to be shared ( Loder et al., 2024 ). Another barrier to reproducibility is that 53% of articles reported relative or mixed p -values, which limits the feasibility of meta-analyses and secondary analyses. Following the lead of several established medical journals ( Aguinis et al., 2021 ), physical therapy journals should require reporting of exact p -values in accordance with standard conventions for decimal formatting ( Lang & Altman, 2015 ). Disconnect Between Hypothesis Statement & Statistical Reporting Only 33% of the quantitative articles explicitly stated a hypothesis, which is substantially lower than in related fields, such as exercise sciences (64%; Twomey et al., 2021 ) and sports medicine (60%; Büttner et al., 2020 ). Together with the relatively high prevalence of effect size reporting (81%), this difference may reflect recent changes in the statistical reporting policies of physical therapy journals. In 2022, an editorial published in several journals, including three of the four journals in our sample, informed researchers that some physical therapy journals in the International Society of Physiotherapy Journal Editors (ISPJE) would expect manuscripts to use estimation methods instead of null hypothesis significance testing ( Elkins et al., 2022 ). This recommendation was met with some critique ( Lakens, 2022a ; Lohse, 2022 ; Tenan & Caldwell, 2022 ) and has since evolved into more nuanced guidelines, emphasizing that “ p- values are only one piece of information that needs to be considered jointly with the uncertainty of estimates, the study context, the costs of different types of errors, and the prior probability of the hypothesis itself” ( Lohse & Kliethermes, 2025 ). These guidelines align with the authors’ apparent reluctance to abandon null hypothesis significance testing altogether, as suggested by its continued use in over half of studies that did not explicitly state a hypothesis. Slow Knowledge Dissemination Preprints serve as a public record of the author’s original manuscript ( Butler & Boisgontier, 2025 ), contributing to transparency by making modifications introduced during peer review and editorial processes visible, and potentially reducing bias at these stages. By bypassing peer-review and publication delays, preprints enable the early dissemination of research results, accelerating scientific discovery ( Maggio et al., 2018 ). Modeling the effects of removing these delays over a 10-year period suggests that discovery could be accelerated up to fivefold ( Quake, 2017 ). These benefits have led several national funding agencies to recognize and encourage preprinting, including those in the countries of the sampled journals: the United States ( National Institutes of Health, 2025 ), Canada ( Canadian Institutes of Health Research, 2023 ), the United Kingdom ( Wellcome, 2025 ), and Australia ( Australian Research Council, 2021 ). Despite this, our results indicate that only 1.3% of physical therapy research is preprinted, delaying knowledge dissemination by over a year, given that the average time from submission to journal publication is 400 days. To promote preprinting, journals should not only allow the submission of preprinted manuscript, but also explicitly encourage this practice in their author guidelines. Additionally, journals could facilitate submissions by enabling direct transfers from preprint repositories, as the Physical Therapy & Rehabilitation Journal (PTJ) does with MedRxiv ( https://www.medrxiv.org/submit-a-manuscript ). Limitation and Future Considerations This study has several limitations that should be noted. First, the study is based on four journals. Although they are the official journal of the main physical therapy associations in their respective countries, future studies should expand the breadth of article sources. Second, we assessed journals that are published within developed countries, which limits the generalizability of the findings. Future research should examine research practices in physical therapy within a global context. Finally, we assessed research practices indirectly, based on articles. Future research should investigate these practices more directly by surveying researchers in physical therapy. Conclusions Our results suggest that the replicability and reproducibility of physical therapy research is deficient. To address these issues, we recommend that the field urgently consider adopting registered reports, mandating open data and code sharing, encouraging preprints, and providing clear author guidance on statistical reporting. Implementing these measures could improve transparency, reduce publication bias, and strengthen the overall credibility of physical therapy research. Data Availability Data, code, and material used for this study are publicly available: https://doi.org/10.5281/zenodo.17138184 https://doi.org/10.5281/zenodo.17138184 ARTICLE INFORMATION Data and Code Availability Data, code, and material used for this study are publicly available: https://doi.org/10.5281/zenodo.17138184 Authorship Contribution Statement Based on the Contributor Roles Taxonomy (CRediT) (Allen et al., 2019), individual author contributions to this work are as follows: François Jabouille, Ata Farajzadeh: Investigation, Formal Analysis, Visualization, Writing – Original Draft; Writing – Review and Editing; Adèle Guillemot Exertier, Jérôme Martine, Natalie Sadek, Leonardo Huet Klinger, Matthew Coman Iliut, Valérie Kapsa: Investigation; Matthieu Boisgontier: Conceptualization, Methodology, Investigation, Data Curation, Formal Analysis, Visualization, Writing – Original Draft, Writing – Review and Editing, Supervision, Project Administration, Funding Acquisition. Funding Matthieu P. Boisgontier is supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) (RGPIN-2021-03153), the Canada Foundation for Innovation (CFI 43661), Mitacs, and the Banting Discovery Foundation. François Jabouille and Ata Farajzadeh are supported by an Admission Scholarship, a Doctoral International Scholarship, and a Special Merit Scholarship from the University of Ottawa. Ata Farajzadeh is supported by a BMO Graduate Scholarship. Conflict of Interest Disclosure The authors declare that they have no financial conflicts of interest related to the content of this article. Matthieu P. Boisgontier is the founder, representative, and manager of Peer Community In (PCI) Health & Movement Sciences ( https://healthmovsci.peercommunityin.org/about ), a free and transparent peer review service provided by a community of researchers who review and approve preprints. 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