Clinical Scenario: Increasing hamstring flexibility through clinical stretching interventions may be an effective means to prevent hamstring injuries. However the most effective method to increase hamstring flexibility has yet to be determined. Clinical Question: For a healthy individual, are proprioceptive neuromuscular facilitation (PNF) stretching programs more effective in immediately improving hamstring flexibility when compared with static stretching programs? Summary of Key Findings: A thorough literature search returned 195 possible studies; 5 studies met the inclusion criteria and were included. Current evidence supports the use of PNF stretching or static stretching programs for increasing hamstring flexibility. However, neither program demonstrated superior effectiveness when examining immediate increases in hamstring flexibility. Clinical Bottom Line: There were consistent findings from multiple low-quality studies that indicate there is no difference in the immediate improvements in hamstring flexibility when comparing PNF stretching programs to static stretching programs in physically active adults. Strength of Recommendation: Grade B evidence exists that PNF and static stretching programs equally increase hamstring flexibility immediately following the stretching program. Keywords: direct, PNF, range of motion Clinical ScenarioInjuries to the posterior thigh are common in athletics. Hamstring injuries result in significant time lost from participation and impair health-related quality of life. 1 Previous research has determined that hamstring injuries are related to poor hamstring flexibility. 2,3 Therefore, increasing hamstring flexibility through clinical stretching interventions may be an effective means to prevent hamstring injuries. It is evident that hamstring stretching, whether using a proprioceptive neuromuscular facilitation (PNF) or static method, can increase hamstring flexibility. However, it is unclear if greater hamstring flexibility can be achieved through PNF or static stretching techniques. Therefore, the purpose of this critically appraised topic was to determine if PNF stretching programs are more effective than static stretching programs in immediately increasing hamstring flexibility in healthy adults. Focused Clinical QuestionFor a healthy individual, are PNF stretching programs more effective in immediately improving hamstring flexibility when compared with static stretching programs? Summary of Search, Best EvidenceAppraised, and Key Findings• Multiple databases were searched for randomized controlled trials of level 2 evidence or higher that compared PNF stretching programs to a static stretching program on the immediate effects on hamstring flexibility. • The literature search produced 329 articles after removal of duplicates; 195 articles were assessed.• Based on the design of the included studies, the PEDro scale was used to critically appraise the methodological quality of each study. 4 Two independent reviewers appraised each study and a consensus score was reached t...