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Table 1 Description of the 7 criteria designed to assess the risk of bias of external validity quality in the studies

From: The Association Between Training Load and Injury Risk in Elite Youth Soccer Players: a Systematic Review and Best Evidence Synthesis

Criterion Description of criteria
1. Definition of soccer-related injury Studies that aimed to investigate soccer-related injuries should present a definition of an injury informing what was considered as an injury in the study.
Studies that present a definition of time-loss injury received a star for this criterion.
2. Representativeness of the exposed cohort (a) Truly representative of the average soccer players in the communitya; (b) somewhat representative of the average soccer players in the communitya; (c) selected group of users; (d) no description of the derivation of the cohort.
3. Ascertainment of exposure (a) Secure recorda; (b) structured interviewa; (c) written self-report; (d) no description.
4. Demonstration that outcome of interest was not present at the start of the study (a) Yesa; (b) no
Studies that described that all soccer players included were injury-free at baseline received a star for this criterion.
5. Assessment of outcome (a) Independent blind assessmenta; (b) record linkagea; (c) self-report; (d) no description.
6. Was follow-up long enough for outcomes to occur? (a) Yesa; (b) no
Studies that carried out a follow-up period of at least 12 weeks received a star for this criterion.
7. Adequacy of follow-up of cohorts (a) Complete follow-up of all subjects accounted fora; (b) subjects lost to follow-up unlikely to introduce bias (up to 20% loss) or description provided of those losta; (c) follow-up rate < 80% and no description of those lost; (d) no statement.
  1. aArticles with this alternative received a star for this criterion