Where this summary comes from
Impellizzeri FM, McCall A, van Smeden M. Why methods matter in a meta-analysis: a reappraisal showed inconclusive injury preventive effect of Nordic hamstring exercise. Journal of Clinical Epidemiology, 2021. PMID 34520846.
The paper itself — doi.org/10.1016/j.jclinepi.2021.09.007
Study design: Reappraisal of a meta-analysis · randomised trials only · 6 trials from the original 15 studies
What the paper asked
That "50% reduction in hamstring injury" from the Nordic exercise — how well is it actually supported?
What was found
- Of the 15 studies the earlier meta-analysis pooled, only 5 had actually randomised participants to the Nordic exercise. The rest were not randomised trials.
- Across those five trials the risk ratio was 0.56, but the 95% confidence interval ran 0.20 to 1.52 — a range that contains both halving the risk and no effect at all.
- Adding one newer trial: risk ratio 0.59, confidence interval 0.27 to 1.29. The prediction interval is wider still: 0.10 to 3.29.
- Their own conclusion: the evidence for a protective effect remains inconclusive and comes mostly from trials at high risk of bias. At best a conditional recommendation, and only for football.
What does not follow from it
- The paper does not say the Nordic exercise is useless. It says the number being advertised does not follow from the available data. Absence of conclusive evidence is not evidence of absence.
- Six trials is a thin base, and the authors themselves call for new ones.
- The question is injury prevention, not strength. The same exercise's effect on eccentric strength and fascicle length is measured in other studies.
What it means for someone here
This summary is here because its lesson matters more than the exercise does: a compelling number — a 50% reduction — turned, once the methods were checked, into a range that settles nothing. Every programme written in this clinic is held to that same standard, rather than to how often something has been recommended.
This page summarises one study. It is not treatment advice, and no programme is written for a person from a single paper.