Static hamstring stretches before a sprint session do almost nothing to protect the muscle from tearing. What actually predicts whether your hamstrings survive a maximal sprint is how well you control the slow, lowering phase of a fairly humble kneeling exercise: the Nordic hamstring curl.
Hamstring strains remain one of sport’s most stubborn injuries, and the numbers explain why coaches obsess over them. Hamstring strains account for up to 37% of all injuries in sprint sports, with re-injury rates exceeding 30%. Despite better warm-ups, better pitches, and more sports scientists on staff than ever, the problem hasn’t gone away. In fact, one review examining a decade of data noted that the incidence of hamstring injuries has not only not decreased in the past 10 years, but has actually increased by 4%. That’s a sobering statistic for anyone still relying on a few toe-touches and leg swings as their main prevention strategy.
Key takeaways
- Why the stretching routine you’ve always done before sprinting provides almost zero protection
- The exact moment during a sprint when hamstring tears actually happen—and why it’s not what most athletes think
- One unglamorous kneeling exercise with evidence so strong it could cut hamstring injuries in half
Why stretching misses the point
The instinct to stretch before sprinting comes from a reasonable, if outdated, idea: tight muscles tear more easily. But hamstring strains during sprinting don’t typically happen because the muscle was too short. They happen during the late swing phase, that split second when your leg is decelerating forward and the hamstring is lengthening rapidly while still trying to contract. Researchers describe this as a stretch-shortening cycle, and in the second half of the swing, the bi-articular hamstring muscles undergo a stretch-shortening cycle, with the greatest stretch seen in the femoral biceps, the hamstring muscle most often injured, and as sprint speed increases, so too does the amount of stretch and negative work of the hamstring muscles.
the muscle is being asked to resist lengthening while under huge tension, not simply to stretch further. Some research has looked at whether static stretching changes this length-tension relationship favourably, and the picture is genuinely mixed. One study found that a rightward shift of length–torque relationship during the late swing phase and reduced peak ground reaction force after effective static stretching may increase the possibility for muscle fibers to shorten before eccentric contraction and decrease the possibility for muscle fibre being overstretched. That sounds promising, but the same body of research acknowledges that static stretching impairs the subsequent explosive strength, which is precisely the quality a sprinter needs on the start line. Stretching, at best, tinkers with the margins. It doesn’t build the raw capacity to absorb force.
The kneeling exercise that actually changes the odds
What does change the odds is eccentric strength, the muscle’s ability to produce force while lengthening under load. And the exercise with the deepest evidence base for building it is the Nordic hamstring curl. The Nordic hamstring curl is an exercise in which a person kneels with their feet fixed in position and lowers their body by extending the knee. A partner (or a fixed anchor, a bar, or specialist equipment) holds the ankles down while you resist gravity on the way down, fighting to keep the descent slow and controlled for as long as possible before catching yourself with your hands.
That lowering phase, the “slow part”, is the whole point of the exercise. The principal way the exercise has been executed by athletes in research is by an eccentric-only muscle action where they gradually lean forward as far as possible until breakpoint and then fall to the floor in a controlled fashion, putting their hands out to catch themselves. The longer and more controlled that descent, the greater the strength adaptation. Some coaches have athletes perform a concentric return as well, pulling themselves back up, though the injury-prevention evidence is built largely on the eccentric-only version.
The scale of the effect is what makes this exercise stand out from almost any other prevention tool in sport. A narrative review pooling dozens of studies concluded that incorporating Nordic hamstring curls into a training regimen can potentially reduce hamstring injury rates by up to 70%. A separate meta-analysis of over 8,000 athletes found that programs including Nordic hamstring exercises reduced hamstring injury rates by roughly 50%, and a systematic review registered with PROSPERO reached a near-identical figure, concluding that programmes that include the NHE reduce hamstring injuries by up to 51%, essentially halving the rate of hamstring injuries across multiple sports in different athletes. Few single interventions in sports medicine carry that kind of weight of evidence.
Getting the technique (and the dosage) right
None of this works if you rush in and do it badly. The exercise is unforgiving on tissue that hasn’t been prepared for it, and jumping straight to full-range, unassisted Nordics is a fast route to days of crippling soreness rather than resilience. Sports scientists studying muscle activation during the movement recommend that coaches consider a methodological exercise progression starting with relatively low demanding exercises, or an assisted Nordic Curl with a band attached to the participant’s back, in order to facilitate control of the overload during the last part of the range of motion. In practice, that means starting with a resistance band taking some of your bodyweight, building the range of motion gradually over several weeks, and prioritising control over how far you can lean.
Frequency matters too. Much of the foundational research on soccer players used a modest schedule: male soccer players did Nordic Hamstring curls twice a week for four weeks and this was found to increase knee flexor eccentric strength. Two sessions a week, low volume to begin with, is enough to start shifting the numbers that matter, fascicle length and eccentric torque, both linked to a lower risk of strain.
It’s worth being honest that Nordics aren’t a magic shield. Some coaches working specifically with sprinters argue that grinding eccentric strength work sits awkwardly alongside the explosive, elastic demands of top-speed running, and that Nordics should complement, not replace, sprint-specific drills and elastic strength training. That’s a fair caution rather than a reason to skip the exercise altogether. The practical takeaway for anyone training seriously, whether that’s five-a-side football, athletics club sessions, or weekend rugby, is to spend less energy folding forward to touch your toes before training and more time twice a week, under control, mastering that slow kneeling descent. As always, if you have an existing hamstring issue or you’re returning from injury, check with a physiotherapist or your GP before adding a new loaded exercise to your programme.
Sources : medrxiv.org | journals.lww.com