There’s a sound people who work in sports learn to recognize.
An athlete pulls up mid-sprint, reaches back for the back of their thigh, and everyone on the sideline knows what’s happened before anything is said.
Hamstring strains are the signature injury of spring sports, and there are good reasons for that. There’s also an unusually strong body of evidence on how to reduce them — stronger than for almost any other injury in sport — and most athletes have never been told about it.
Here’s both halves.
When It Actually Happens
Hamstring strain injuries predominantly occur during sprinting — specifically during the late-swing phase of the running cycle.
That’s the moment just before your foot hits the ground, when your leg is swinging forward and your hamstring has to decelerate it. The muscle is lengthening while generating high force, at extended length, at speed.
That’s the most demanding thing you can ask a muscle to do, and it’s why hamstring injuries cluster in sports involving maximum-velocity running: track, soccer, lacrosse, and any sport with open-field sprinting.
The muscle most often affected is the biceps femoris long head, on the outer side of the back of your thigh — because it experiences elevated fiber stress at extended lengths during exactly that phase.
There’s a second mechanism too, less common but worth knowing: stretch-type injuries from movements taking the hamstring to extreme length — high kicks, slide tackles, hurdles, or a leg extended awkwardly for a ball. These behave differently and sometimes take longer to resolve than they look like they should.
Why Spring Specifically
Three things converge.
You haven’t sprinted in months. Winter training rarely involves maximum-velocity running, even when it involves plenty of conditioning. Your hamstrings have not been exposed to the specific demand that injures them.
The season starts with maximum effort. Tryouts and early practices ask for full-speed work almost immediately.
And preseason strength imbalances haven’t been addressed — which turns out to matter considerably.
The Preseason Screening Data
This is where the evidence gets pointed.
Research has found that soccer players with uncorrected preseason hamstring strength imbalance had a significantly higher rate of hamstring strain injury than those without an imbalance — and, importantly, than those whose imbalance was identified and corrected before the season.
That third group matters. It suggests this isn’t simply a matter of identifying who’s doomed; correcting the imbalance changed the outcome.
The numbers attached to strength ratios are striking. Professional soccer players with a hamstring-to-quadriceps strength ratio below a certain threshold on preseason testing were found to have around a three-fold higher risk of hamstring strain during the season. In competitive sprinters, a low preseason hamstring-to-quadriceps peak torque ratio was associated with a substantially greater increase in risk again.
The practical translation: quadriceps that are strong relative to hamstrings is a measurable, addressable risk factor — and preseason is when to find it.
The Intervention With Unusual Evidence
Now the part worth acting on.
The Nordic hamstring exercise — a partner-assisted movement where you kneel and lower your torso forward under control, resisting with your hamstrings — has been studied extensively.
A systematic review and meta-analysis covering 8,459 athletes concluded that including the Nordic hamstring exercise in injury prevention programs halves the rate of hamstring injuries.
Meta-analyses have reported an average effect around a 51% reduction in injury rates when it’s incorporated into training.
For context, that’s an unusually large effect for a preventive intervention in sport. Very few things reduce a common injury by half.
Why it works: the exercise requires the biceps femoris long head to generate force while lengthening eccentrically — the same action that occurs during sprinting, though at slower velocities. It builds capacity in exactly the mechanism that fails.
The Practical Details Nobody Mentions
Three findings that change how you’d actually implement it.
It takes at least six weeks. In one randomized trial, players had to train for a minimum of six weeks before maximal eccentric force improved significantly. Improvement was detectable at week six but not at week four.
So starting the week of tryouts achieves very little. This is a preseason intervention, and it needs a genuine runway.
High volume isn’t necessary. That same trial compared a high-volume group (21 sessions, 538 total repetitions) against a low-volume group (10 sessions, 144 repetitions) over eight weeks. Both increased maximal eccentric force, with no significant difference between groups.
That’s genuinely useful. A modest, sustainable dose appears to deliver the benefit — which matters, because the most common reason this exercise fails is that athletes stop doing it.
And it doesn’t slow you down. A persistent concern among coaches is that eccentric work might blunt sprint or jump performance. In studies examining this, sprint performance and jump height did not decline. One of the reasons teams have historically been reluctant to use it turns out not to hold up.
About Reinjury
This is the part that should change how seriously you take the return-to-play phase.
Reinjury rates after an acute hamstring strain have been reported between 14% and 63% within a season or within two years — and reinjuries tend to be more severe than the original.
Data from professional soccer found that around 18% of all hamstring injuries were recurrences, with over two-thirds occurring within two months of return to play.
Which identifies the danger window precisely. The first two months back is when most reinjuries happen, and it’s exactly when athletes feel recovered and want to resume normal training.
Returning because it stopped hurting is how the 63% figure gets populated.
What a Proper Return Involves
Briefly, because this deserves individual guidance:
Symptoms settled at rest, with full pain-free range.
Strength restored, with attention to the eccentric side specifically, and reasonable symmetry between legs.
Graded return to running, then to high-speed running — because you cannot rehabilitate a sprinting injury without eventually sprinting.
Testing at speed, not just at jogging pace. A hamstring that behaves at 70% tells you little about 95%.
And continued eccentric work after return, given that danger window.
Returning to full sprinting without having sprinted in rehabilitation is the single most common error, and it’s why so many athletes go down again in the same month.
What to Do This Week
If your season hasn’t started: begin eccentric hamstring work now, twice weekly, and give it at least six weeks. Add high-speed running exposure before you’re asked to sprint competitively.
If your season has started: start anyway. The evidence is for programs run through the season, not just before it.
If you’ve had one before: you’re in the highest-risk group, and previous injury is consistently among the strongest predictors. That warrants a proper assessment rather than hoping.
And do it consistently. Compliance is the variable that determines whether any of this works — the effect sizes above come from athletes who actually did the program.
When to Get It Assessed
Seek prompt assessment for any hamstring injury involving a pop or sudden sharp pain with loss of function; significant bruising; an inability to walk normally; pain high up near the sitting bone, which can indicate a different injury with different management; or any hamstring problem that keeps recurring.
Pain right at the sitting bone that’s been building gradually — rather than a sudden strain — is often a different condition entirely and needs its own approach.
Get Screened Before You Need Us
Preseason is when hamstring risk is identifiable and addressable. Mid-season is when it’s a rehabilitation problem.
Sports PT Centers offers a free discovery visit at no cost and no obligation. You’ll get an assessment of your strength, movement, and injury history, an honest picture of where your risk sits, and a program you can realistically keep up through a season.
If you’re returning from a hamstring injury, we’ll build the progression properly — including the speed work most programs skip.