Comparisons of hamstring flexibility between individuals with and without low back pain: systematic review with meta-analysis

ABSTRACT

Background: There is no robust evidence on the contribution of reduced hamstring flexibility to the development of low back pain (LBP) in cohort studies.

Purpose: To investigate whether individuals with LBP have impaired hamstring flexibility and stiffness and what measures have been used to compare hamstring flexibility and stiffness between individuals with and without LBP.

Methods: A systematic literature search was undertaken in PubMed, EMBASE, MEDLINE, CINAHL, SCOPUS, and Cochrane databases from inception to April 2018. The GRADE system was used to determine the quality of evidence for each measure evaluated in meta-analysis.

Results: Respectively, seventeen and two studies having acceptable methodological quality were analyzed with regard to hamstring flexibility and stiffness. Four measures were identified for hamstring flexibility and five for stiffness. Meta-analyses were undertaken in straight leg raising (SLR), sit and reach and knee extension in 90° hip flexion for hamstring flexibility and for hamstring stiffness measures of stiffness at 50° SLR and gradient of stiffness from 20° to 50° SLR (M_e-grad). Significantly reduced hamstring flexibility or increased stiffness (P < .05) was detected in SLR, 90/90 knee extension and M_e-grad. However, the validity of measures for hamstring flexibility was problematic and GRADE scores for all measures in the meta-analyses were very low.

Conclusion: There have been four measures for hamstring flexibility and five for stiffness to evaluate individuals with and without LBP. It was impossible to conclude whether individuals with LBP have impaired hamstring flexibility and stiffness due to very low quality of evidence for meta-analyses.

KEYWORDS:

• Hamstring muscle tightness
• low back pain
• systematic review
• meta-analysis

Acknowledgments

The authors wish to acknowledge: Mr. Markus Kiel, Mr. Georg Supp and Dr. Annina Schmid for helping evaluation of methodological quality of a study written in German; Ms. Kana Nishimoto for assisting GRADE rating; Mr. Musashi Yasuda and Mr. Tatsuya Noguchi for assisting data extraction; and Dr. Toby Hall for English proofreading before paper submission.

Declaration of Interest

The authors declare no conflict of interest.