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Table 10 The levels and grade of evidence scaling criteria applied to the articles.

From: A systematic review of the evidence for Canada's Physical Activity Guidelines for Adults

Level of Evidence Criteria
Level 1    Randomized control trials without important limitations
Level 2    • Randomized control trials with important limitations
     • Observational studies (non-randomized clinical trials or cohort studies) with overwhelming evidence
Level 3 Other observational studies (prospective cohort studies, case-control studies, case series)
Level 4 Inadequate or no data in population of interest
  Anecdotal evidence or clinical experience
Grade of Evidence Criteria
Grade A Strong recommendation (action can apply to most individuals in most circumstances)
     • Benefits clearly outweigh risks (or vice-versa)
     • Evidence is at Level 1, 2, or 3
Grade B Weak recommendation (action may differ depending on individual's characteristics or other circumstances)
     • Unclear if benefits outweigh risks
     • Evidence is at Level 1, 2, or 3
Grade C Consensus recommendation (alternative actions may be equally reasonable)
     • Unclear if benefits outweigh risks
     • Evidence is at Level 3 or 4