Overview
biceps femoris
The lateral hamstring muscle, involved in the majority of sprinting-related strains.Interesting facts
- • The name comes from butchery: the tendons at the back of the knee were used to hang ham in curing.
- • Hamstring strain is the most common muscle injury in football and athletics, and re-injury rates within a season have historically been very high.
- • The Nordic hamstring curl is one of the few sports injury prevention exercises with strong, replicated evidence — trials show roughly a 50% reduction in hamstring injury rates.
- • Biceps femoris has two heads with different nerve supplies, and its long head accounts for the large majority of sprinting-related strains.
- • Perceived hamstring tightness is often a neural or protective phenomenon rather than genuine muscle shortness — many people with 'tight' hamstrings have normal muscle length.
Common misconceptions
- Tight hamstrings are the cause of most low back pain.
The association is weak and often reversed — protective muscle guarding from back pain frequently produces the tightness rather than the other way around. - Stretching prevents hamstring strains.
Static stretching has not been shown to reduce strain rates. Eccentric strengthening has, consistently and substantially. - You cannot touch your toes because your hamstrings are short.
Toe-touch limitation is frequently neural tension or lumbar and hip movement restriction rather than actual muscle length. - Once you tear a hamstring you are always prone to it.
Re-injury risk is high mainly when rehabilitation is cut short. Completing an eccentric strength programme to full capacity substantially reduces it.
Anatomy & how it works
Three muscles run from the sitting bone down to the shin, dividing around the back of the knee.
Biceps femoris (long head)
The lateral hamstring, crossing hip and knee; responsible for the large majority of sprinting strains.
Biceps femoris (short head)
Crosses only the knee and has a separate nerve supply, making its coordination with the long head a proposed injury factor.
Semitendinosus
A medial hamstring with a long tendon, frequently harvested as a graft for ACL reconstruction.
Semimembranosus
The deepest medial hamstring, a powerful hip extensor and knee flexor.
Ischial tuberosity
The sitting bone where the hamstrings originate — the site of proximal tendinopathy and avulsion injuries.
Musculotendinous junction
The transition between muscle and tendon, where the majority of acute strains occur.
eccentric contraction
A muscle producing force while lengthening — the loading pattern responsible for most hamstring strains and the basis of their prevention.Primary functions
- • Extending the hip during running, walking and hinging
- • Flexing the knee
- • Decelerating the shin at the end of the swing phase in sprinting
Secondary functions
- • Assisting rotation of the flexed knee
- • Contributing to knee joint stability alongside the ACL
- • Storing and returning elastic energy during running
Across a lifetime
- Development
- Hamstring flexibility is high in young children and declines through adolescence, particularly during rapid growth phases when bone lengthens faster than muscle adapts.
- Childhood
- Apophyseal avulsion at the sitting bone occurs in adolescent athletes whose growth plates have not yet fused, and presents differently from an adult strain.
- Adulthood
- Peak incidence of acute hamstring strain occurs in sprinting and multidirectional sport, with risk rising sharply after age 25 in athletic populations.
- Later life
- Proximal hamstring tendinopathy becomes more common, presenting as deep sitting-bone pain that worsens with prolonged sitting and hill running.
- Sex differences
- Acute sprinting strains are more frequently reported in male athletes, largely reflecting sport participation patterns; proximal tendinopathy affects women at least as often.
Body connections
Beyond sport, hamstring strength contributes to safe hinging and lifting, to knee stability, and to walking efficiency. Proximal hamstring tendinopathy is a common and often persistent cause of pain on sitting, which disproportionately affects desk-based work and quality of life.
Body connections
How this links to the rest of you
Both extend the hip; when gluteal strength is inadequate the hamstrings take a disproportionate share of the work and fatigue faster.
The hamstrings resist forward shear of the shin, sharing load with the ACL and directly influencing knee stability.
The posterior chain works as a unit during running, with calf stiffness and hamstring loading closely coupled.
Hamstring tension alters pelvic tilt, changing lumbar spine resting position and load distribution during hinging.
Hamstring length and strength influence pelvic control during gait and hinging patterns.
How lifestyle changes it
Exercise
Eccentric strength training is the best-evidenced injury prevention measure available for this muscle group — and it also improves sprint performance.
Nutrition
Protein adequacy supports muscle repair; nothing hamstring-specific beyond general sports nutrition applies.
Hydration
Dehydration is associated with cramping, though the causal evidence for hamstring strain specifically is weak.
Sleep
Sleep restriction is associated with increased soft tissue injury rates in athletes, one of the more consistent findings in sports medicine.
Stress
High life and competition stress correlate with elevated injury rates, likely mediated through recovery and attention.
Ageing
Eccentric strength declines with age faster than concentric, which is part of why strain risk rises in masters athletes.
Environment
Cold conditions without adequate warm-up, and fatigue late in matches, are both established situational risk factors.
Genetics
Certain collagen gene variants have been associated with hamstring injury susceptibility, though effect sizes are small and not clinically actionable.
Symptoms & conditions
Common symptoms
Common conditions
Rare conditions
- • Complete proximal hamstring avulsion
- • Ischial apophyseal avulsion in adolescents
- • Sciatic nerve entrapment at the hamstring origin
Acute & chronic problems
- • Acute hamstring strain (grades 1–3)
- • Sprinting-type biceps femoris tear
- • Stretching-type semimembranosus tear
- • Proximal hamstring tendinopathy
- • Recurrent hamstring strain
- • Chronic hamstring weakness after incomplete rehabilitation
Early warning signs
- • A tightening or 'grabbing' sensation late in a run
- • Deep sitting-bone pain that worsens with prolonged sitting
- • Noticeable side-to-side difference in hamstring strength
- • Reduced sprint speed without other explanation
Risk factors
- • Previous hamstring injury — by far the strongest predictor
- • Low eccentric hamstring strength
- • Increasing age in athletes
- • Sudden increases in high-speed running volume
- • Fatigue and inadequate recovery
Protective factors
- • Regular Nordic curl or equivalent eccentric training
- • Progressive exposure to high-speed running
- • Complete rehabilitation after any strain
- • Adequate sleep and recovery
Optimise & recover
Prevention
- • Include Nordic hamstring curls or an equivalent eccentric exercise at least twice weekly if you sprint or play field sport
- • Build exposure to high-speed running gradually rather than sprinting only in competition
- • Address gluteal strength so the hamstrings are not overloaded as substitute hip extensors
- • Prioritise sleep during heavy training blocks
Recovery
- • Begin gentle pain-free loading within days rather than resting completely
- • Progress to eccentric loading and then to high-speed running before returning to sport
- • Use objective strength and running-speed criteria for return, not just absence of pain
Hamstring rehabilitation has been transformed by two findings: that early loading beats prolonged rest, and that criteria-based return — restoring eccentric strength and high-speed running exposure before returning to sport — substantially reduces re-injury. Programmes emphasising lengthened-position exercises such as the Askling L-protocol have shown faster return times than conventional protocols.
Movement library
- Beginner
Leg swings
Dynamic pre-run mobility that prepares the hamstring for the swing-phase demands of running.
- Intermediate
Sciatic nerve glides
Addresses neural tension, which frequently underlies the sensation of hamstring tightness.
- Advanced
Nordic hamstring curl
The best-evidenced hamstring injury prevention exercise, loading the muscle eccentrically at long lengths.
- Intermediate
Romanian deadlift
Loads the hamstrings in a lengthened hip-hinge position and builds posterior chain strength.
- Intermediate
Single-leg deadlift
Addresses side-to-side asymmetry, itself a documented injury risk factor.
- Advanced
Glute-ham raise
Trains hip extension and knee flexion together, matching the hamstring's dual-joint role.
- Beginner
Sliding leg curl
An accessible eccentric option for those not yet strong enough for full Nordics.
- Beginner
Supine hamstring stretch with strap
Controlled lengthening that avoids the lumbar flexion of a standing toe-touch.
- Beginner
Standing hip hinge stretch
Lengthens the hamstrings while maintaining a neutral spine.
Soft tissue work provides short-term relief for muscular tightness. Direct compression over the sitting bone should be avoided in proximal hamstring tendinopathy, where it aggravates symptoms.
Habits worth building
- • Add Nordics or sliding curls to two sessions a week and keep them in year-round, not just pre-season
- • Avoid sitting on hard surfaces for long periods if you have sitting-bone pain
- • Do not return to sprinting on the basis of pain alone — test strength and speed first
Nutrition, devices & products
Hamstring nutrition is general muscle repair nutrition: sufficient protein spread through the day, adequate carbohydrate to fuel high-speed running, and enough total energy to support adaptation from eccentric training, which is particularly demanding.
Foods to prioritise
- • 1.4–2.0 g protein per kg body weight during training or rehabilitation
- • Adequate carbohydrate around high-intensity sessions
- • Sufficient total energy — under-fuelling markedly increases soft tissue injury risk
Foods to limit
- • Alcohol, which impairs muscle repair and is associated with increased injury rates in athletes
- • Chronic energy deficiency during heavy training
| Supplement | Evidence | Note |
|---|---|---|
| Creatine monohydrate | Strong | Supports strength and repeat-sprint capacity; indirectly relevant through improved training quality. |
| Protein supplementation | Strong | Useful for meeting total protein targets during rehabilitation, with no advantage over food otherwise. |
| Collagen with vitamin C | Emerging | Some evidence for tendon adaptation when timed before loading; most relevant to proximal tendinopathy. |
| Tart cherry juice | Limited | Small effects on perceived soreness after eccentric exercise; unclear whether it affects adaptation. |
Devices & wearables
- • Nordic curl straps or benches
- • Furniture sliders for sliding leg curls
- • Resistance bands for graded rehabilitation loading
- • GPS units tracking high-speed running distance, widely used in professional sport for load management
Professional treatments
- • Physiotherapy-led criteria-based rehabilitation
- • Shockwave therapy for proximal hamstring tendinopathy
- • Ultrasound or MRI for grading significant tears
- • Surgical repair for complete proximal avulsion
Educational mention only, not a recommendation: NSAIDs, used cautiously and short-term as they may interfere with muscle repair (clinician-guided), Simple analgesia to enable early loading.
When to seek medical care
Most hamstring strains can be managed with progressive loading, but a sudden pop with inability to walk, or extensive bruising, suggests a significant tear that warrants imaging and specialist assessment — complete proximal avulsions have better outcomes with early surgical repair.
Seek care promptly if you notice
- • Audible pop with immediate inability to bear weight
- • Extensive bruising spreading down the back of the thigh
- • A palpable gap in the muscle or tendon
- • Numbness, tingling or weakness in the foot
- • Sitting-bone pain with fever or unexplained weight loss
Research & frequently asked questions
Current research
- Research continues into why Nordic curl adherence remains low in professional sport despite strong evidence, and into shorter effective dosing protocols.
1
American Journal of Sports Medicine · 2011
Preventive effect of eccentric training on acute hamstring injuries in men's soccer
Cluster-randomised trial in Danish football found the Nordic hamstring programme substantially reduced both new and recurrent hamstring injuries across a season.
- Work is ongoing to identify reliable return-to-play criteria that reduce re-injury below current rates.
2
British Journal of Sports Medicine · 2013
Acute hamstring injuries in Swedish elite football: a randomised controlled trial of two rehabilitation protocols
Trial comparing lengthening-focused exercises with conventional rehabilitation found significantly faster return to full training without increased re-injury.
Emerging therapies
- • Blood flow restriction training for early-stage loading after injury
- • Platelet-rich plasma injection for proximal tendinopathy, where evidence remains mixed
Scientific controversies
- • Whether platelet-rich plasma injection offers any benefit over exercise for hamstring injury is disputed, with several negative trials.
- • Optimal Nordic curl dosing — how few sets are enough to retain the protective effect — is still being defined.
A 2011 Scandinavian trial demonstrating that Nordic hamstring exercise halved injury rates in footballers is one of the clearest single results in sports injury prevention, and it shifted hamstring management decisively from stretching toward eccentric strength.
Frequently asked questions
Do Nordic curls really prevent hamstring injuries?
Yes — this is one of the best-evidenced findings in sports injury prevention, with multiple trials and meta-analyses showing roughly a halving of injury rates. The main obstacle is adherence, since the exercise is demanding.
Should I stretch my hamstrings to prevent strains?
Static stretching has not been shown to reduce strain rates. Eccentric strengthening has. Stretching may help symptomatically with perceived tightness but should not be relied on for prevention.
How long does a hamstring strain take to heal?
Grade 1 strains typically allow return in 1–3 weeks, grade 2 in 4–8 weeks, and grade 3 considerably longer. Return should be based on restored strength and high-speed running capacity, not the calendar.
Why does my sitting bone hurt when I sit for a long time?
That pattern is characteristic of proximal hamstring tendinopathy. It responds to progressive loading and to avoiding sustained compression, such as sitting on hard surfaces or deep hip flexion positions.
Why can't I touch my toes even though I stretch?
Toe-touch range depends on lumbar flexion, hip mobility and neural tension as well as muscle length. Many people who cannot touch their toes have entirely normal hamstring length.
Explore further
Keep exploring
Glossary
- Eccentric contraction
- A muscle producing force while lengthening — the loading pattern responsible for most hamstring strains and the basis of their prevention.
- Biceps femoris
- The lateral hamstring muscle, involved in the majority of sprinting-related strains.
- Ischial tuberosity
- The sitting bone, where the hamstring tendons originate.
- Musculotendinous junction
- The interface between muscle and tendon, the most common site of acute strain.
- Nordic hamstring curl
- A partner- or strap-assisted exercise lowering the torso from kneeling, loading the hamstrings eccentrically.
Trusted organisations & further reading
- NHS — Sprains and strains
- British Journal of Sports Medicine
- Rehab Science — Tom Walters. Practical progressive rehabilitation programming for hamstring and posterior chain injuries.
- Return to Play in Football — Volker Musahl et al. (eds). A clinical reference on criteria-based return to sport, including hamstring protocols.
Medical disclaimer
This page is for general education and does not replace personalised medical advice. If you have concerning symptoms, or before starting a new supplement, medication or exercise programme, speak with a qualified healthcare professional.