Does the Nordic Hamstring Exercise Really Halve Hamstring Injuries? Reading the Meta-Analysis and the Re-Analysis

A sprint, then a sharp pull at the back of the thigh. The Nordic hamstring exercise (NHE) — kneeling and slowly lowering the body forward — is the go-to prevention tool, and you may have heard that it "cuts hamstring injuries in half." Reading the 2019 meta-analysis behind that claim alongside a 2021 re-analysis, the fairest summary today is: the effect points toward fewer injuries, but it is not yet certain.

What the study looked at

The original study (van Dyk et al., 2019) is a systematic review and meta-analysis of 15 studies and 8,459 athletes across sports, comparing programs that included the NHE with usual training or programs without the NHE.

The re-analysis (Impellizzeri et al., 2021, Journal of Clinical Epidemiology) revisited that work to show how study selection can drive a meta-analysis's conclusions. It included only randomized trials in which athletes were randomly assigned to the NHE, and recalculated the effect.

Key findings

Original meta-analysis (2019)

Programs including the NHE had a hamstring injury risk ratio of 0.49 (95% CI 0.32–0.74)
Restricting to 8 randomized trials gave 0.52; excluding studies at high risk of bias gave 0.55
The authors concluded the NHE reduces hamstring injuries by up to 51% — roughly halving them

Re-analysis (2021)

Of the original 15 studies, only 5 randomly assigned athletes to the NHE
Across those 5 trials, the risk ratio was 0.56 (95% CI 0.20–1.52)
Adding one newer trial gave 0.59 (95% CI 0.27–1.29)
Because the confidence intervals cross 1 (no difference), the effect was judged inconclusive

How to read this in practice

The re-analysis did not show that the NHE does not work. Both analyses point toward fewer injuries
But when limited to rigorous trials, the uncertainty is large, and "it halves injuries" is too strong a claim
It is also hard to separate the effect of the whole program from the effect of the NHE alone
A sensible approach: include the NHE as one part of injury prevention, without relying on it alone. It is a demanding exercise, so start with low volume and progress based on how athletes respond

Keeping athletes healthy and available is also the foundation for their development over a season. That is exactly why it pays to understand how strong the evidence really is.

Using ATHCON

In ATHCON's daily check-in, athletes report soreness and pain, which are compared with their own 14-day baseline and classified into four levels. When introducing a soreness-inducing exercise like the NHE, you can use those changes to decide how quickly to progress volume.

ATHCON does not predict or diagnose injuries. The classification is a prompt to check in with the right athletes.

Takeaways

The 2019 meta-analysis reported roughly half the hamstring injuries with NHE programs (risk ratio 0.49)
The 2021 re-analysis of 5 rigorous trials found a risk ratio of 0.56 — inconclusive
The direction favors fewer injuries, but do not over-rely on it; start with low volume