Hold-relax and contract-relax (PNF) stretching for hamstrings flexibility: large immediate gains versus no intervention, conflicting results versus static stretching
Systematic review with meta-analysis
Sample
39 randomized controlled trials, n=1770 healthy adults (aged ≥18, with or without a pathological condition); median PEDro score 4/10. Databases searched from inception to 31 March 2014 and updated to 31 May 2017.
Key Findings
Immediately after 1 session, vs control (no intervention): large effect — 6 trials, SMD = 1.02 (95% CI 0.69 to 1.35), I² = 2%
After multiple sessions, vs control: large effect — 4 trials, SMD = 1.02 (95% CI 0.64 to 1.40), I² = 0%
Vs static stretching: meta-analysis showed conflicting results — PNF is not shown to beat static stretching for hamstrings flexibility
Vs other techniques: individual trials conflicting
Authors' conclusion: the immediate effects of HR and CR on hamstrings flexibility are better than no intervention; long-term effects against other stretching types and the optimal prescription parameters need further research
Mechanism
Not from this paper: contract-relax and hold-relax protocols are usually explained by post-isometric (autogenic) inhibition — a brief contraction followed by stretch transiently lowers reflex resistance; the neurophysiology of reduced motoneurone excitation during stretch is in REF-391. The meta-analysis measured flexibility, not tone or stiffness.
Practical Application
Pooling 39 RCTs (n=1770 healthy adults), hold-relax / contract-relax stretching gave a large immediate gain in hamstrings flexibility over doing nothing (SMD 1.02) and the same after repeated sessions — but results against ordinary static stretching were conflicting, so PNF is a proven flexibility tool, not a proven upgrade on static stretching.
Not from this paper: PNF, like static stretching, produces an acute performance decrement when done immediately before exercise (-4.4% for PNF, -3.7% for static stretching in REF-268); keep it away from race warm-ups and hard sessions
Not from this paper; the base's own practice: a contract-relax dose of a brief submaximal contraction, a short relax, then a held stretch, repeated a few times per muscle, in the evening or on recovery days; hip flexors, hamstrings, calves and glutes for cyclists. The optimal parameters are explicitly unresolved in this review.
Do not sell PNF as a "stiffness reducer": the outcome here is flexibility (ROM), and trial quality is low (median PEDro 4/10)
Limitations
Low median trial quality (PEDro 4/10); heterogeneous PNF protocols
Hamstrings only; healthy adults, not athletes specifically
Few trials enter each pooled comparison (6 and 4)
Long-term comparison with other stretching types unresolved
How this entry was checked and changed
Why this level
regraded 2026-09-27 from A: pooled trials are mostly small and of low quality (median PEDro 4/10); only 6 and 4 trials enter the two meta-analyses
Content correction 2026-09-27
Journal/title mismatch: entry cited "J Bodywork Mov Ther 23(3):561-574"; the DOI on file resolves to Cayco et al., Phys Ther Sport 35:42-55. Header corrected to the DOI's paper.
"11 studies, n=455", "PNF vs static: SMD ≈ +0.3-0.5", "significant acute reductions in stiffness (larger than static)", "~4% deficit", "6-10 s maximal contraction", "contract 6-10 s at ~75% max, relax 2-3 s, hold 20-30 s, 3-5 times", "≥3 h before sleep", "within 30 min" -> not in the abstract; abstract gives 39 trials, n=1770, SMD 1.02 vs control and conflicting results vs static stretching. Removed or relabelled as house practice without numbers.
Cross-reference to REF-233 pointed at an unrelated entry (muscle cramps) and was dropped. Level A -> A- (low-quality small trials); Sport cycling -> general; Tier 1 -> mixed 0-2.
Cross-references to duplicate stubs repointed to their canonical entries (REF-393->REF-268); the stubs were emptied on 2026-09-27.