The methods for this systematic review followed the principles outlined in the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Statement (PRISMA) [16]. This study was registered on the International Prospective Register of Ongoing Systematic Reviews (PROSPERO) (Reg No: CRD42019134586) to avoid duplication of the research during the review process.
Eligibility criteria
Observational, cohort, epidemiological studies assessing the incidence and prevalence of injury and illness in single day and multi-stage mountain marathon cycling races were included in the study, provided they met the criteria of the UCI cross-country marathon category [2]. Prospective and retrospective studies of races longer than 60 km, over one or more days; professional and recreational or amateur events including non-UCI accredited races, of longer than 60 km, and studies that included mountain bikers over 18 years of age were eligible [17]. No date limitation was applied to the studies. Articles written in English or professionally translated into English with evidence of forward and backward translation for accuracy were included.
Outcome measures
The primary outcome measures were the incidence or prevalence of injury and illness sustained during the event. Secondary outcome measures included the severity and location of the reported injuries, type of injury, rider’s ability to continue in the event, prevalence of injury preceding the event, pre-event training distances and the experience/expertise of the riders (novice, semi-professional, professional). Illness diagnosis, severity and the rider’s ability to continue in the event were additional secondary outcome measures. The definition of injury, illness and severity (of both) used in the study was noted.
Data sources and search strategy
The following databases were searched: PubMed, CINAHL (EbscoHost), Scopus, PEDRO and the Cochrane library. Congress abstracts from cycling specific and clinical sports congresses (for example Cycling Science Conference and Winter Cycling Congress) held in the past ten years and available online were reviewed to identify unpublished studies. A grey literature search in Google Scholar was performed following the database searches. The reference lists of eligible articles, identified during the search, were manually searched.
Databases were searched using the following keywords: (Mountain OR off-road OR cross-country OR races OR racing OR stage race) AND (Bicycling [MeSH]) OR cycling OR biking OR bikers OR cyclists OR bicycl*) AND (Injuries OR injury OR falling OR Illness OR epidemiology) AND (soft tissue OR fractures OR concussion OR skin abrasions OR gastrointestinal OR respiratory OR dehydration). The database and grey literature searches took place on 5 January 2021 and included all relevant publications up to this date.
Following the keywords search, all abstracts and titles were downloaded to Covidence (Covidence systematic review software, Veritas Health Innovation, Melbourne, Australia. Available at www.covidence.org).
Data screening and extraction
Two independent researchers (KB and LC) screened the title and abstracts for eligibility based on the above-mentioned criteria. The two reviewers were given independent access to the platform and rated each abstract and title for inclusion or exclusion. Upon disagreement on the inclusion or exclusion of an article, the reviewers discussed and reached consensus on the article’s eligibility.
Following title and abstract screening, both reviewers independently reviewed the full text articles for final eligibility and inclusion into the review. The reviewers discussed and reached consensus on the inclusion of specific studies if there was disagreement between the two reviewers. Once the articles were included, the reviewers extracted the appropriate data from the text.
Data were extracted by the reviewers independently, on participants (age and sex), cycling event (length of stages, total race length, environmental conditions and type of cycling), injury (area of injury, diagnostic practitioner and time off cycling), illness (type of illness, diagnostic practitioner, severity, time off event and whether the rider had a full recovery), study design, and risk of bias using a pre-designed data extraction form.
Risk of bias and quality assessment
The AXIS tool for critical appraisal of cross-sectional studies was used to assess the reporting quality and risk of bias [18]. The tool provides 20 questions, with seven addressing each quality of reporting and quality of design, and six on potential areas of bias. Each question was answered as ‘yes’, ‘no’ or ‘don’t know/unclear’. The AXIS tool does not provide a numeric scoring system to classify responses as high or low, but allows subjectivity in the interpretation, based on the individual questions [18].
Bias assessment
Risk of bias was assessed based on the selection of participants, respondents and non-respondents (and the reason for non-responses) and the internal consistency of the studies. Risk of bias was reported as ‘unclear’ if the required information was not provided by the authors.
Quality of reporting
Reporting quality assessment included questions on whether the aims, population and methods were clearly reported in the article. Results and limitations need to be adequately described and discussed. Studies were recorded as ‘unclear reporting quality’ if the content of these questions was not reported in the study.
Quality of design
The quality of design was evaluated on its appropriateness for the aims of the study and the justification of the sample size and frame. Conflicts of interests and ethical approval were assessed in this section.
Data synthesis
Descriptive tables of all data are presented. All injury and illness data were reported as an incidence (per time period) or as prevalence (percentage). Descriptive summary tables were populated with information from each study, including study design, participants, context (events, distance, environment) and outcomes (injury or illness, ability to continue riding).
A narrative analysis of the types, severity and area of injuries and illness type and severity was performed. A quantitative analysis would have been performed if there were three or more studies with sufficient data reported in the same format or with the same definitions of injury and illness, as either incidence or prevalence. Following risk of bias assessment, the same two reviewers decided on the exclusion of the studies in a meta-analysis based on the above criteria. Sub-group analyses of age, sex, type of cycling and experience were not conducted due to the insufficient information available in the studies, and differences in study design and definitions.