How to Strengthen Your Hamstrings: An Evidence-Based Guide to Eccentric Training and Injury Prevention

The strongest hamstrings are not the ones that contract the hardest — they’re the ones that resist being pulled apart. That single shift in framing is the foundation of every modern hamstring injury prevention program, and it’s why one exercise — the Nordic hamstring curl — has been shown to cut hamstring strain rates by roughly half across pooled randomized trials.¹

Most muscles get stronger by contracting. Your hamstrings get healthier by lengthening under load. The technical word for that is eccentric — the muscle is producing force while it’s being stretched, not while it’s shortening. And the meta-analytic evidence on eccentric hamstring training is now over 20 years deep.²³

This guide is the working playbook: why hamstrings break the rules of normal strength training, what the research actually says, how to tell if your hamstrings are weak (and by how much), the best exercises ranked by evidence, an 8-week Nordic progression, and the mistakes that quietly sabotage everything.

Why Hamstring Training Is Different From Every Other Muscle

Hamstrings are the only major lower-body muscle group that crosses two joints — the hip and the knee — and that biarticular geometry is exactly why they get hurt.⁴ When you sprint, your foot is still flying forward while your hamstrings are already firing to slow it down. The muscle is producing peak force while it’s stretching to its longest length. That’s the eccentric phase of late swing, and it’s where roughly 80% of hamstring strains happen.⁴

Now look at how most people train hamstrings: seated leg curls, lying leg curls, sometimes a Romanian deadlift. These are all heavily concentric — the muscle shortens against the resistance.

Here’s the mismatch:

Where hamstrings get hurt: lengthening under high force, hip flexed, knee extending, late-swing sprinting (~6–8× bodyweight peak force in the biceps femoris long head).⁵
Where most people train them: shortening under moderate force, lying prone, hips neutral, no sprint specificity.

Train the wrong end of the contraction spectrum and your “strong” hamstrings can still snap the moment you sprint for a bus or chase a kid down a soccer field. The fix isn’t to do more hamstring work — it’s to do the right kind.

The Evidence: What 20+ Years of Research Says About the Nordic Hamstring Curl

The Nordic hamstring curl is the most-studied injury prevention exercise in sports medicine, and the effect sizes are unusual for any field — let alone exercise science.

The landmark 2011 trial by Jesper Petersen and colleagues at the University of Copenhagen randomized 942 male Danish soccer players to a 10-week Nordic curl program or control. Eccentric hamstring training reduced overall hamstring injury rates by approximately 60–65% and recurrent hamstring injuries by approximately 85%.⁶ The number needed to treat to prevent one recurrent injury was three players. That’s the kind of effect you almost never see in a non-pharmacological intervention.

Four years later, Nick van der Horst and team at UMC Utrecht replicated the protocol in 579 amateur Dutch soccer players. Hamstring injuries dropped by roughly 50% in the Nordic group.⁷

By 2019, Nicol van Dyk and colleagues had pooled the literature in a systematic review and meta-analysis published in the British Journal of Sports Medicine. The headline result: programs that include the Nordic hamstring exercise reduce hamstring injuries by up to 51%.¹ An earlier 2017 meta-analysis by Wesam Al Attar’s team had reached a similar conclusion — an injury risk ratio of 0.490, statistically significant, in soccer players.⁸

Why does this work? Roald Mjølsnes and Roald Bahr’s group at the Norwegian School of Sport Sciences ran a 10-week head-to-head trial of Nordic curls vs. traditional concentric hamstring training in well-trained soccer players. Eccentric strength rose 11% in the Nordic group; the concentric group saw no significant change in eccentric strength at all.⁹ Concentric work doesn’t transfer. Eccentric work transfers to the exact strength quality that fails when hamstrings tear.

There’s a cruel epilogue to this story. Roald Bahr, Kristian Thorborg, and Jan Ekstrand surveyed 32 UEFA Champions League and 18 Norwegian Premier League teams across three seasons. Despite the published evidence, 83.3% of club-seasons were classified as non-compliant with the Nordic protocol.¹⁰ The exercise works. Adherence is the bottleneck.

SensAI treats Nordic curl frequency as a programmable variable rather than a willpower problem — the AI coach schedules eccentric sessions into the week and reminds you when one’s been skipped, which is exactly the failure point the Bahr survey identified.

How to Tell If Your Hamstrings Are Weak (And By How Much)

Hamstring weakness rarely shows up on a leg curl machine. It shows up under three specific conditions: when one leg is asymmetrically weaker than the other, when knee flexor strength can’t keep pace with quadriceps strength, and when the muscle is being asked to produce force at long lengths.

The benchmarks from the literature:

Functional H:Q ratio below 0.6 — the ratio of hamstring eccentric strength to quadriceps concentric strength. Below this threshold, hamstring strain risk rises measurably in professional soccer players.¹¹
Bilateral asymmetry above 10–15% — when one hamstring is 10–15% weaker than the other on eccentric strength testing, injury risk in the weaker leg roughly doubles. David Opar’s group at Australian Catholic University, co-developers of the NordBord eccentric strength dynamometer, has been the most consistent voice on asymmetry as the leading modifiable risk factor.¹²
15–25% eccentric deficit on a previously injured side — once a hamstring has been strained, the eccentric strength of the affected limb tends to remain depressed compared to the contralateral side, and that residual deficit is a strong predictor of re-injury.¹²

You don’t need a NordBord to spot trouble. Try this at home:

Signs your hamstrings need eccentric work:

Single-leg Romanian deadlift hold: standing on one leg, hinge the torso forward to parallel and hold for 30 seconds. If one side wobbles dramatically more than the other or you can’t hold the position, you have a control and length-tension problem.
Single-leg glute bridge endurance: lie on your back, one heel on the floor, lift hips. If you fail before 20 reps on one side and not the other, you have an asymmetry.
A history of even one minor hamstring “tweak.” Re-injury rates after a hamstring strain are notoriously high, especially in the first two months.¹³
You only train hamstrings on machines or with deadlifts — no eccentric exposure at long muscle lengths.
You sprint, jump, or change direction in your sport but never train the hamstring’s lengthening capacity.

SensAI’s AI coach watches single-leg load and rep performance over time across exercises like Bulgarian split squats and single-leg RDLs, flags developing left-right asymmetries, and slots in unilateral correctives before the weaker side becomes a strain. If you’ve been wondering is your training actually working, asymmetry trends are one of the cleanest signals.

The Best Hamstring Exercises, Ranked by Evidence

If you can only do one hamstring exercise per week, the literature points to the Nordic curl — or a regression of it. Everything else is supplementary.

Exercise	Primary Stimulus	Equipment	Evidence Base	Best For
Nordic hamstring curl	Eccentric, knee-dominant, long-length	Partner or strap	Strongest — multiple RCTs and meta-analyses¹⁶⁷	Injury prevention; sprinters; field-sport athletes
Romanian deadlift	Eccentric, hip-dominant, long-length	Barbell or DBs	Strong — biomechanical loading at long lengths	Bilateral hip-hinge strength; runners; general strength
Single-leg RDL	Eccentric + balance, hip-dominant, unilateral	Dumbbell or kettlebell	Strong — addresses bilateral asymmetry	Asymmetry correction; runners; injury rehab
Hip thrust / glute bridge	Concentric, hip-dominant, short-length	Barbell or bodyweight	Moderate — hypertrophy and glute co-contraction	Glute development; lockout strength; novice lifters
Razor / slider curl	Eccentric, knee-dominant	Slider or stability ball	Emerging — Nordic regression for low-strength athletes	Beginners; rehab; partnerless training
Seated/lying leg curl	Concentric, knee-dominant, short-length	Machine	Limited for injury prevention	Hypertrophy adjunct; bodybuilding

A three-sentence read on each:

Nordic hamstring curl. Kneel, anchor your ankles, and lower your torso forward as slowly as you can without flexing at the hips. Catch yourself on your hands once you can no longer resist, then push back up. This is the only exercise repeatedly shown in controlled trials to cut hamstring strain rates.¹⁶

Romanian deadlift. Hinge at the hips with a soft knee bend, letting the bar travel down the front of your legs to mid-shin or just below the knee, then return. The RDL trains the hamstrings eccentrically at the hip — different stimulus, complementary effect to the Nordic. Pair with hip mobility work if your hinge is restricted.

Single-leg RDL. The unilateral version of the RDL, performed with one foot grounded and the opposite leg trailing. This is the exercise of choice when you’ve identified a left-right asymmetry, and it trains the gait-specific demand that runners actually face.

Hip thrust / glute bridge. A glute-dominant hip extension exercise that loads the hamstring concentrically at a short length. Useful for hypertrophy and glute strength, weak as a strain-prevention stimulus on its own.

Razor curl / slider curl. A bodyweight regression of the Nordic for athletes who can’t yet control the full range. Works the same eccentric pattern with a fraction of the loading.

Seated/lying leg curl. Pure concentric, short-length knee flexion. Mjølsnes’ trial showed it does not transfer to eccentric strength gains.⁹ Treat it as accessory hypertrophy work, not as injury prevention.

SensAI picks the right regression based on your training age, current eccentric capacity, and recovery state — partner-assisted Nordics in week one, slider curls if your knees can’t tolerate the kneeling position, full Nordics with a tempo as strength climbs.

An 8-Week Nordic Hamstring Progression

The protocol below is modeled on the volumes from Mjølsnes (2004) and the Petersen (2011) field intervention.⁶⁹ It assumes a healthy, recreationally active adult with no current hamstring injury.

Weeks 1–2 — Familiarization

Frequency: 1 session/week
Volume: 2 sets × 5 reps
Tempo: 3-second eccentric (descending phase)
Setup: partner-assisted return on the way back up; if no partner, use a strap or band to assist

Weeks 3–4 — Build

Frequency: 2 sessions/week
Volume: 2 sets × 6 reps
Tempo: 4-second eccentric
Setup: continue partner or band assist; aim to control further into the descent each week

Weeks 5–6 — Load

Frequency: 3 sessions/week
Volume: 3 sets × 6–8 reps
Tempo: 4–5 second eccentric
Setup: minimize assistance, hands catching only at the very end of range

Weeks 7–8 — Maintain

Frequency: 1 session/week (Petersen maintenance dose)
Volume: 3 sets pyramid — 12, 10, 8 reps
Tempo: 4-second eccentric, controlled return
Setup: use a small explosive return and full eccentric on the way down

A few rules of execution. Keep your hips fully extended throughout — the moment you fold at the waist, you’ve offloaded the hamstrings onto the lumbar spine. Resist the descent for as long as you can, then catch the floor; do not flop. And expect significant soreness in weeks 1–3 — DOMS following the first few Nordic sessions is unusually intense even for trained athletes.¹⁴

That soreness is information, not a sign to stop. If the soreness is severe, drop a set or extend rest between sessions, but don’t abandon the protocol. SensAI’s recovery-aware programming pushes the next eccentric session out a day if your wearable’s HRV and sleep signals say you’re undercooked, which lets you actually finish the 8 weeks instead of bailing in week 3.

For Runners: Why Your Hamstrings Need Eccentric Work Even More

Sprinting puts your hamstrings under loads that no gym exercise replicates. The biceps femoris long head — the most commonly strained hamstring muscle — generates peak forces of roughly 6–8× bodyweight in late swing.⁵ That’s the moment your foot is decelerating just before ground contact, and it’s where strains happen.

Recreational runners are not exempt. The mechanism is the same at any sprint speed; only the absolute force scales down. If you do strides, intervals, hill repeats, or sport that involves any sprinting, your hamstrings are accumulating eccentric stress whether you train for it or not.

A workable add-on for runners: 2–3 sessions per week of Nordic curls (use the protocol above) plus single-leg RDLs once or twice a week. The single-leg RDL specifically addresses the bilateral, gait-specific demand of running — left and right are loaded asymmetrically, just like every stride.

SensAI integrates running data from Garmin, Apple Watch, Coros, and other wearables through HealthKit, so the AI coach actually sees your weekly running load and programs hamstring work that complements rather than competes with mileage — heavier eccentric volume in deload weeks, lighter maintenance work the day after a long run.

Common Hamstring Training Mistakes

Most hamstring training failures aren’t about exercise selection — they’re about how the work gets implemented. The patterns below show up over and over in case histories.

Skipping eccentric work because you’re sore. Initial Nordic-induced DOMS is dramatic but transient. Skipping the next session is the most common reason adherence falls apart and the protocol stops working.¹⁰¹⁴
Stretching cold hamstrings to “prevent” strain. Static stretching before activity has weak evidence for strain prevention and may even reduce force production briefly. Warm up dynamically, train eccentrics for prevention.
Doing hamstring work after heavy squats or deadlifts when fatigued. Eccentric work performed under heavy fatigue is lower quality and higher risk. Do Nordics earlier in the session or on a separate day from peak lower-body lifts.
Rushing the descent on Nordic curls. The whole stimulus is the slow lowering. Drop in 1 second and you’ve trained almost nothing.
Ignoring left/right strength differences. A 15% asymmetry in eccentric strength is a doubling of injury risk in the weaker leg.¹² Unilateral exercises are non-negotiable for athletes with any limb dominance issue.

A practical knock-on: weak hamstrings shift load to the lumbar erectors and can quietly contribute to lower back pain and posterior-chain dysfunction. Similarly, the hamstrings are key knee-joint stabilizers, and chronic eccentric weakness can show up downstream as knee pain under loaded knee flexion.

Frequently Asked Questions

How often should I train my hamstrings? Two to three eccentric sessions per week is the volume validated by the trial literature for injury prevention.⁶⁹ Once-weekly maintenance dosing preserves gains after a build phase.⁶

Can I do Nordic curls without a partner? Yes. Use a strap or band looped around an immovable object to anchor your ankles, or use a sturdy couch or weight bench with the legs under a padded bar. For the assist on the way up, you can push off the floor with your hands — the eccentric phase is the only one that matters for the strength adaptation.

Do hamstring stretches prevent injury? The evidence for static stretching as a strain prevention tool is weak. Eccentric strength training has 20+ years of trial data showing it works; stretching does not.¹² Stretch for mobility and feel-good reasons, not for strain prevention.

How long until Nordic curls reduce my injury risk? Petersen’s trial showed protective effects after a 10-week loading phase, with benefits maintained on once-weekly dosing thereafter.⁶ Plan for 10–12 weeks of consistent training before reassessing.

Should women train hamstrings differently? The eccentric prescription is the same. The added context: women have higher ACL injury rates than men in cutting and jumping sports, and strong, well-trained hamstrings are part of the protective mechanism for the knee. Eccentric hamstring training is, if anything, more important for active women — not less.

Train the lengthening. Track the asymmetry. Be patient with the soreness. Twenty years of trial data is unanimous on what works for hamstrings. The remaining question is whether you’ll actually do it for ten weeks straight — and that’s the part most programs, and most people, get wrong.

References

van Dyk N, Behan FP, Whiteley R. “Including the Nordic hamstring exercise in injury prevention programmes halves the rate of hamstring injuries: a systematic review and meta-analysis of 8459 athletes.” British Journal of Sports Medicine, 2019. PMID: 30808663. https://pubmed.ncbi.nlm.nih.gov/30808663/ ↩ ↩² ↩³ ↩⁴ ↩⁵
Al Attar WSA, Soomro N, Sinclair PJ, Pappas E, Sanders RH. “Effect of Injury Prevention Programs that Include the Nordic Hamstring Exercise on Hamstring Injury Rates in Soccer Players: A Systematic Review and Meta-Analysis.” Sports Medicine, 2017. PMID: 27752982. https://pubmed.ncbi.nlm.nih.gov/27752982/ ↩ ↩²
Bourne MN, Timmins RG, Opar DA, Pizzari T, Ruddy JD, Sims C, Williams MD, Shield AJ. “An Evidence-Based Framework for Strengthening Exercises to Prevent Hamstring Injury.” Sports Medicine, 2018. PMID: 29116573. https://pubmed.ncbi.nlm.nih.gov/29116573/ ↩
Opar DA, Williams MD, Shield AJ. “Hamstring strain injuries: factors that lead to injury and re-injury.” Sports Medicine, 2012. PMID: 22239734. https://pubmed.ncbi.nlm.nih.gov/22239734/ ↩ ↩²
Schache AG, Dorn TW, Blanch PD, Brown NAT, Pandy MG. “Mechanics of the human hamstring muscles during sprinting.” Medicine & Science in Sports & Exercise, 2012. PMID: 21912301. https://pubmed.ncbi.nlm.nih.gov/21912301/ ↩ ↩²
Petersen J, Thorborg K, Nielsen MB, Budtz-Jørgensen E, Hölmich P. “Preventive effect of eccentric training on acute hamstring injuries in men’s soccer: a cluster-randomized controlled trial.” American Journal of Sports Medicine, 2011. PMID: 21825112. https://pubmed.ncbi.nlm.nih.gov/21825112/ ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷
van der Horst N, Smits DW, Petersen J, Goedhart EA, Backx FJG. “The Preventive Effect of the Nordic Hamstring Exercise on Hamstring Injuries in Amateur Soccer Players: A Randomized Controlled Trial.” American Journal of Sports Medicine, 2015. PMID: 25794868. https://pubmed.ncbi.nlm.nih.gov/25794868/ ↩ ↩²
Al Attar WSA, Soomro N, Sinclair PJ, Pappas E, Sanders RH. “Effect of Injury Prevention Programs that Include the Nordic Hamstring Exercise on Hamstring Injury Rates in Soccer Players.” Sports Medicine, 2017. PMID: 27752982. https://pubmed.ncbi.nlm.nih.gov/27752982/ ↩
Mjølsnes R, Arnason A, Østhagen T, Raastad T, Bahr R. “A 10-week randomized trial comparing eccentric vs. concentric hamstring strength training in well-trained soccer players.” Scandinavian Journal of Medicine & Science in Sports, 2004. PMID: 15387805. https://pubmed.ncbi.nlm.nih.gov/15387805/ ↩ ↩² ↩³ ↩⁴
Bahr R, Thorborg K, Ekstrand J. “Evidence-based hamstring injury prevention is not adopted by the majority of Champions League or Norwegian Premier League football teams: the Nordic Hamstring survey.” British Journal of Sports Medicine, 2015. PMID: 25995308. https://pubmed.ncbi.nlm.nih.gov/25995308/ ↩ ↩²
Croisier JL, Ganteaume S, Binet J, Genty M, Ferret JM. “Strength imbalances and prevention of hamstring injury in professional soccer players: a prospective study.” American Journal of Sports Medicine, 2008. PMID: 18448578. https://pubmed.ncbi.nlm.nih.gov/18448578/ ↩
Bourne MN, Timmins RG, Opar DA, Pizzari T, Ruddy JD, Sims C, Williams MD, Shield AJ. “An Evidence-Based Framework for Strengthening Exercises to Prevent Hamstring Injury.” Sports Medicine, 2018. PMID: 29116573. https://pubmed.ncbi.nlm.nih.gov/29116573/ ↩ ↩² ↩³
Askling CM, Tengvar M, Tarassova O, Thorstensson A. “Acute hamstring injuries in Swedish elite sprinters and jumpers: a prospective randomised controlled clinical trial comparing two rehabilitation protocols.” British Journal of Sports Medicine, 2014. PMID: 24620041. https://pubmed.ncbi.nlm.nih.gov/24620041/ ↩
Ekstrand J, Hägglund M, Waldén M. “Epidemiology of muscle injuries in professional football (soccer).” American Journal of Sports Medicine, 2011. PMID: 21335353. https://pubmed.ncbi.nlm.nih.gov/21335353/ ↩ ↩²