Hold-relax and contract-relax stretching for hamstrings flexibility: A systematic review with meta-analysis.

OBJECTIVE: To synthesize evidence on the effects of hold-relax and contract-relax stretching (HR and CR) on hamstrings flexibility compared with no intervention and other stretching techniques.

DESIGN: Electronic databases (PubMed, PEDro, Cochrane CENTRAL, Scopus, LILACS) were searched from inception until March 31, 2014 and updated until May 31, 2017. Randomized controlled trials involving HR and CR to improve hamstrings flexibility in adults (aged ≥18 years old) with or without a pathological condition were included. Two reviewers independently searched literature, assessed risk of bias, and extracted data, while a third reviewer settled disagreements.

RESULTS: Thirty-nine trials (n = 1770 healthy adults; median PEDro score = 4/10) were included. Meta-analysis showed large effects compared to control immediately after 1 session (6 trials, SMD = 1.02, 95% CI = 0.69 to 1.35, I2  = 2%) and multiple sessions (4 trials, SMD = 1.02, 95% CI = 0.64 to 1.40, I2  = 0%). Meta-analysis showed conflicting results compared to static stretching, while individual trials demonstrated conflicting results compared to other techniques.

CONCLUSIONS: The immediate effects of HR and CR on hamstrings flexibility in adults are better against control. The long-term effects against other stretching types, and optimal exercise prescription parameters require further research.