Flexibility Statistics: Norms, Methods & Effects

Static stretching increased hamstring flexibility by about 12 degrees on the passive straight-leg raise compared with no stretching (95% CI 9.6-14.5)

Meta-analysis of 19 controlled trials in healthy young adults. The passive and active knee-extension tests improved by about 8.6 and 8.4 degrees.

Stretch training produced large range-of-motion gains (effect size 0.93), and ROM was still above baseline after 2-6 weeks off (0.55)

Meta-analysis of 13 studies with 556 participants and programs of 5-15 weeks. ROM fell slightly once stretching stopped (-0.41), and only participants who stayed active kept their gains.

Spreading stretching over at least 5 days a week, for at least 5 minutes a week, was linked to ROM gains; time within a single session was not

Review of 23 long-term studies. Weekly frequency was positively associated with ROM, and static protocols outperformed ballistic and PNF stretching over the long term.

Static stretches shorter than 30 seconds had no detrimental effect on maximal performance (pooled change -1.1%), and 30-45 seconds had no significant effect either (-1.9%)

Systematic review of 106 studies. Significant losses became likely with stretches of 60 seconds or more, regardless of task, contraction type or muscle group.

Tested straight after stretching, performance changed by -3.7% after static stretching, -4.4% after PNF and +1.3% after dynamic stretching

Systematic review. Testing came on average 3-5 minutes after stretching, and most studies added no dynamic activity in between; when they did, no clear performance effect remained.

Static stretching of 60 seconds or more per muscle cut performance by 4.6%, against 1.1% for under 60 seconds

Same review. Static stretching gave a 2.2% performance benefit when the muscle worked at long lengths.

Acute range-of-motion gains from a single stretching session typically last less than 30 minutes

True of static, dynamic and PNF stretching alike. Static and PNF stretching had no clear effect on all-cause or overuse injuries; no injury data exist for dynamic stretching.

Stretching did not prevent sports injuries (risk ratio 0.963), while strength training cut them to less than a third (0.315)

Meta-analysis of 25 randomized trials with 26,610 participants and 3,464 injuries. Proprioception training gave a risk ratio of 0.550 and multi-component programs 0.655.

Strength training and stretching improved range of motion equally: effect size -0.22 (95% CI -0.55 to 0.12), not significant

Meta-analysis of 11 randomized trials with 452 participants. No difference appeared for active or passive ROM or by joint, though the trials varied widely in design.

Five weeks of full-range resistance training improved hamstring, hip-flexion and hip-extension flexibility as much as static stretching

25 untrained adults randomized to resistance training or stretching, with 12 inactive controls. Both groups beat the controls; the authors call the study preliminary.

Stretching the calves for one hour a day for six weeks improved maximal strength, muscle thickness and flexibility as much as hypertrophy training

69 active participants. The stretching group needed up to 7 hours a week against 3 × 15 minutes of resistance training, which the authors say strongly limits its practical use.

Foam rolling before exercise improved flexibility by 4.0% (g = 0.34) and sprint performance by 0.7%

Meta-analysis of 21 studies. Effects on jump (-1.9%) and strength (+1.8%) were negligible. Rolling after exercise reduced perceived muscle pain (g = 0.47).

A single 90-second static stretch produced 30% viscoelastic stress relaxation in the hamstrings, but stiffness returned to baseline within an hour

Review of laboratory studies. Three weeks of stretching raised ROM through greater stretch tolerance rather than changes in the muscle's passive properties.

In 674 healthy people aged 2-69, women had greater joint mobility than men in nearly all joints and every age group

Goniometer measurements by nine physical therapists. ROM declined with age in both sexes, and the sex gap was largest for ankle plantarflexion and forearm rotation.

Yoga reduced short-term chronic low-back pain with a moderate effect: standardized mean difference -0.48

Meta-analysis of 10 randomized trials with 967 patients. Back-specific disability improved by -0.59 short term; the long-term pain effect was -0.33. No serious adverse events.

In 88 Norwegian adolescents, low-back pain was associated with below-average hamstring flexibility and hip flexion and above-average BMI

Cross-sectional study, mean age 14.7. It shows an association, not that tight hamstrings cause back pain.

18.3% of 12,853 UK adults were classified as hypermobile in a population survey

Questionnaire-based survey in Aberdeen and Cheshire. After adjusting for age and sex, hypermobile participants were 40% more likely to report the most severe chronic widespread pain; the authors call the link modest.