Item	Item No	Recommendation from the STROBE Statement	STROBE-SIIS Extension	Soo Hoo et al. (2018)	Shimizu et al. (2017)	Wessels et al. (2012)	Mutsuzaki et al. (2014)	Huzmeli et al. (2017)	Rocco and Saito (2006)	Curtis and Black (1999)	Hollander et al. (2020)
Title and abstract	1	(a) Indicate the study’s design with a commonly used term in the title or the abstract		Yes	Yes	Yes	No	Yes	No	Yes	Yes
		(b) Provide in the abstract an informative and balanced summary of what was carried out and what was found	SIIS-1.1. Include information on the sport, athlete population (sex, age, geographic region) and level of competition. SIIS-1.2. Include the duration of observation (e.g., one season, one year, multiple years).	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Introduction
Background/rationale	2	Explain the scientific background and rationale for the investigation being reported		Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Objectives	3	State specific objectives, including any pre-specified hypotheses	SIIS-3.1. State whether study was registered. Identify the registration number and database used. SIIS-3.2. State the specific purpose of your study (e.g., to describe the injury burden associated with Olympic-level rowing)	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Methods
Study design	4	Present key elements of study design early in the paper	SIIS-4.1. Clearly specify which health problems are being observed. SIIS-4.2. State explicitly which approach was used to record the health problem data, including all outcome measures or tools SIIS-4.3. State explicitly which coding system was used to classify the health problems (e.g., OSIICS, SMDCS, ICD, etc.) SIIS-4.4. Where relevant, clearly describe how athletes were categorized. Variables to consider could include the type of athlete and/or sport, the environment in which the sport occurs (e.g., type of course or playing area), the typical duration of the sport, the degree of physical contact permitted in the sport and the equipment permitted.	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Setting	5	Describe the setting, locations and relevant dates, including periods of recruitment, exposure, follow-up and data collection	SIIS-5.1. Describe the location, level of play, dates of observation and data collection methods (i.e., who, what, where). SIIS-5.2. Specify the dates of the surveillance period and how the data were handled when the study covered more than one season/calendar year. SIIS-5.3. Define whether the health problem data were collected prospectively or retrospectively.	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Participants	6	(a) Cohort study—give the eligibility criteria and the sources and methods of selection of participants. Describe methods of follow-up Case-control study—give the eligibility criteria and the sources and methods of case ascertainment and control selection. Give the rationale for the choice of cases and controls Cross-sectional study—give the eligibility criteria and the sources and methods of selection of participants	SIIS-6.1. Define the population of athletes and how they were selected and recruited.	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
		(b) Cohort study—for matched studies, give matching criteria and number of exposed and unexposed Case-control study—for matched studies, give matching criteria and the number of controls per case		Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Variables	7	Clearly define all outcomes, exposures, predictors, potential confounders and effect modifiers. Give diagnostic criteria, if applicable	SIIS-7.1. Justify why you measured your primary and secondary outcomes of interest in the specific way chosen. SIIS-7.2. Describe the method for identifying your health predictor	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Data sources/measurement	8	For each variable of interest, give sources of data and details of methods of assessment (measurement). Describe comparability of assessment methods if there is more than one group	SIIS-8.1. Specify who collected/reported the data for the study and their qualifications (e.g., qualified doctor, data analyst, etc.). SIIS-8.2. Specify who coded the data for the study and their qualifications (e.g., qualified doctor, data analyst, etc.). In many instances, this will not be the same as SIIS-8.1. SIIS-8.3. Specify the direct methods used to collect the data and the use of physical documents or any electronic tools. If extracting information from existing sources, specify the data source. SIIS-8.4. Specify the timing of and window for data collection (e.g., day health problem occurred or following day). Specify the frequency of data collection (e.g., daily, weekly, monthly). SIIS-8.5. Report the duration of surveillance (e.g., tournament, season, whole year, playing career).	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Bias	9	Describe any efforts to address potential sources of bias	SIIS-9.1. Clearly report any validation or reliability assessment of the data collection of tools. SIIS-9.2. Formally acknowledge any potential biases in associated with the data collection method (e.g., self- report, recall bias, reporting by nonmedically trained staff, etc.)	No	No	No	No	No	No	No	No
Study size	10	Explain how the study size was arrived at		No	Yes	Yes	Yes	Yes	No	Yes	Yes
Quantitative variables	11	Explain how quantitative variables were handled in the analyses. If applicable, describe which groupings were chosen and why	SIIS-11.1 Explain in detail how multiple injuries/illness episodes are handled both in individual athletes and across athletes/surveillance periods. SIIS-11.2. Specify how injury severity was calculated.	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Statistical methods	12	(a) Describe all statistical methods, including those used to control for confounding	SIIS-12.1. Specify how exposure to risk has been adjusted for and specify the units (e.g., per participant, per athlete exposure, etc.). SIIS-12.2 Specify how relevant risk measures (incidence, prevalence, etc.) were calculated. SIIS-12.3. When relevant to the study aim, specify how injury occurred.	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
		(b) Describe any methods used to examine subgroups and interactions		Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
		(c) Explain how missing data were addressed	SIIS-12.4. For studies reporting multiple health problems, state clearly how these were handled (e.g., time to the first injury only, ignoring subsequent return to play and reinjuries, or modeling of all injuries). SIIS-12.5. Explain how/if athletes not included at outset (e.g., those already injured) were handled in the analyses.	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
		(d) Cohort study—if applicable, explain how loss to follow-up was addressed Case-control study—if applicable, explain how matching of cases and controls was addressed Cross-sectional study—if applicable, describe analytical methods taking account of sampling strategy	SIIS-12.6. In longitudinal studies, it is particularly important to explain how athlete follow-up has been managed. For example, what happened if a player was transferred to another team or has been censored (for those no longer part of the study due to removal during the observation period). Censoring can occur when athletes are removed due to transfer out of the team/study, injury/illness or due to study design.	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
		(e) Describe any sensitivity analyses		Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Results
Participants	13	(a) Report numbers of individuals at each stage of study—e.g., numbers potentially eligible, examined for eligibility, confirmed eligible, included in the study, completing follow-up and analyzed	SIIS-13.1. Clearly state the number of athletes followed-up, the number (and %) of those with the health problem and the number of problems reported among them (a median number of problems per affected athlete could be useful). SIIS-13.2. For studies over multiple seasons/years, report the total numbers of health problems for each year and numbers common to each period.	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
		(b) Give reasons for non-participation at each stage	SIIS-13.3. Report how athletes removed (e.g., due to transfer of teams or time-out due to injury or illness) impact upon data at key data collection/reporting points, ideally with a flow diagram	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Descriptive data	14	(a) Give characteristics of study participants (e.g., demographic, clinical, social) and information on exposures and potential confounders	SIIS-14.1. Include detail on the level of competition being observed (e.g., by age levels, skill level, sex, etc.).	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
		(b) Indicate number of participants with missing data for each variable of interest		Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
		(c) Cohort study—summarize follow-up time (e.g., average and total amount)		NA	NA	NA	NA	NA	NA	NA	NA
Outcome data	15	Cohort study—report numbers of outcome events or summary measures over time	SIIS-15.1. In many observational studies, individuals will sustain more than one health problem over the surveillance period. Take care to ensure descriptive data representing both the number of health problems and the number of athletes affected. It is important to represent effectively both the analysis and reporting of correct units for frequency data, i.e., the % of affected athletes or the % of injuries, body regions, etc.	NA	NA	NA	NA	NA	NA	NA	NA
		Case-control study—report numbers in each exposure category, or summary measures of exposure		NA	NA	NA	NA	NA	NA	NA	NA
		Cross-sectional study—report numbers of outcome events or summary measures		Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Main results	16	(a) Give unadjusted estimates and, if applicable, confounder-adjusted estimates and their precision (e.g., 95% confidence interval). Make clear which confounders were adjusted for and why they were included	SIIS-16.1. Report exposure-adjusted incidence or prevalence measures with appropriate confidence intervals when presenting risk measures. SIIS-16.2. Report details of interest, such as mode of onset	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
		(b) Report category boundaries when continuous variables were categorized		Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
		(c) If relevant, consider translating estimates of relative risk into absolute risk for a meaningful time period		No	No	No	No	No	No	No	No
Other analyses	17	Report other analyses conducted—e.g., analyses of subgroups and interactions, and sensitivity analyses	SIIS-17.1 Report injury diagnosis information, including region and tissue type in tabular form.	No	No	No	No	No	No	No	No
Discussion
Key results	18	Summarize key results with reference to study objectives		Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Limitations	19	Discuss limitations of the study, taking into account sources of potential bias or imprecision. Discuss both direction and magnitude of any potential bias	SIIS-19.1. Discuss limitations in the data collection and coding procedures adopted, including in relation to any risk measures calculated.	Yes	Yes	Yes	Yes	No	No	Yes	Yes
Interpretation	20	Give a cautious overall interpretation of results considering objectives, limitations, multiplicity of analyses, results from similar studies and other relevant evidence		Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Generalizability	21	Discuss the generalizability (external validity) of the study results	SIIS-21.1. Discuss the generalizability of the athlete study population, and health problem subgroups of interest, to broader athlete groups.	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Other information
Funding	22	Give the source of funding and the role of the funders for the present study and, if applicable, for the original study on which the present article is based		Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Ethics	23		SIIS-23.1. Outline how individual athlete data privacy and confidentiality considerations were addressed, in line with the Declaration of Helsinki.	No	Yes	Yes	Yes	No	No	No	Yes