What a hamstring strain is
A hamstring strain is a tear in one of the three muscles at the back of the thigh, most commonly the biceps femoris long head, injured during the late swing phase of sprinting when the muscle is lengthening under high tension.
A second pattern, less common, involves the semimembranosus close to the sitting bone and happens in stretching-type movements such as a high kick or a slide tackle. Those tend to be less painful initially and take considerably longer to recover.
Grading runs from I, a minor strain with minimal strength loss, through II, a partial tear with clear weakness, to III, a complete rupture. Most sporting injuries are grade I or II.
What causes it
The injury happens when the demand of high-speed lengthening exceeds what the muscle can absorb. That is why it clusters around sprinting, and why exposure to high-speed running in training is protective rather than risky when it is built up properly.
The strongest risk factor by a wide margin is a previous hamstring injury, particularly one in the last twelve months. Age and reduced eccentric strength follow it.
Risk factors
- A previous hamstring injury, especially within the last year
- Low eccentric hamstring strength, which is measurable and trainable
- Insufficient exposure to high-speed running in training before demanding it in a match
- Fatigue, with injuries clustering in the closing stages of each half
- Increasing age
- A sudden spike in training load or match minutes
The most common error in hamstring rehab is returning to sprinting once the muscle no longer hurts. Strength deficits and altered muscle architecture persist well beyond symptom resolution, and that gap is where the re-injury rate lives. Criteria worth meeting before full return: symmetrical eccentric strength within about 10 per cent of the other side, full pain-free range, and completion of a progressive sprinting programme at match speed.
What the evidence says
The Nordic hamstring exercise has the strongest preventive evidence of any single exercise in sports medicine. Meta-analyses report reductions in hamstring injury rates of around 50 per cent or more in teams that implement it consistently, and it also reduces re-injury.
Progressive high-speed running exposure is protective. Programmes that build sprint volume gradually before full match exposure show lower injury rates than those that avoid sprinting until the last moment.
Lengthened-state strengthening, such as Romanian deadlifts and single-leg variants performed through a full range, has better evidence than shortened-range work for changing muscle architecture and reducing risk.
Return-to-play decisions based on objective criteria produce lower re-injury rates than decisions based on time elapsed or symptoms alone.
Platelet-rich plasma injection for hamstring strains has been tested in several randomised trials and has not shown benefit over placebo for time to return to play.
Recovery timeline
Grade I strains typically take two to three weeks to a return to sport, grade II four to eight weeks, and grade III considerably longer, often three months or more. Proximal injuries near the sitting bone are consistently slower, sometimes taking three months even when the initial pain seemed mild.
Meeting the strength and sprinting criteria matters more than the calendar. An athlete at four weeks who has met them is safer to return than one at eight weeks who has not.
| Stage | ✓ Do this | ✗ Avoid this |
|---|---|---|
| Days 1–5 | Protect and load lightly. Pain-free isometric holds. Walk normally as soon as you can. | Aggressive stretching, which can extend the tear |
| Weeks 1–3 | Progressive strengthening through increasing range, adding lengthened-state work. Begin jogging. | Sprinting because jogging feels fine |
| Weeks 3–6 | Nordic curls and Romanian deadlifts. Structured build-up of running speed toward match pace. | Skipping the high-speed running build-up |
| Return to play | Meet the criteria: symmetrical eccentric strength, full range, completed sprint progression. | Returning on symptoms alone, which is where re-injuries come from |
How we treat it at Kingsway
Rehabbing a hamstring
The assessment establishes which muscle and which part of it, how much strength has been lost, and what the return-to-play target actually looks like for your sport.
- Palpation to locate the injury and distinguish a sprinting-type from a stretching-type strain
- Strength testing at multiple knee angles, compared with the other side and recorded
- Soft tissue work and manual lymphatic drainage in the early phase where swelling and bruising are present
- Progressive loading programme building toward Nordic curls and lengthened-state work
- A written high-speed running progression toward match pace
- Clear return-to-play criteria agreed at the outset
A course of four to eight sessions across the rehab period is typical, with the frequency higher in the first fortnight and then spacing out as the running programme takes over. For anyone with a history of repeated hamstring injuries, a maintenance programme afterwards matters more than the rehab itself.
When to get it checked
Book an assessment for any hamstring injury that produced a limp or stopped you mid-activity, and particularly for a repeat injury. Get seen promptly for pain high up near the sitting bone with bruising, since proximal injuries need a different plan and are frequently underestimated.
See a doctor or go to A&E if
- A pop or tearing sensation with immediate inability to walk
- Extensive bruising appearing rapidly down the back of the thigh
- A palpable gap in the muscle
- Numbness or pins and needles down the back of the leg into the foot
- Pain high at the sitting bone that is severe and worse on sitting, which can indicate an avulsion
Common questions
When can I sprint again?
When you have met objective criteria rather than a date: eccentric strength within about 10 per cent of the other leg, full pain-free range, and a completed progressive running programme that has already had you at match speed in training.
Returning on the absence of pain alone is the most common route to a repeat injury.
Should I stretch it?
Gentle range work is appropriate early. Aggressive stretching of a fresh tear can extend the injury and is worth avoiding in the first fortnight.
Lengthened-state strengthening, which loads the muscle through a long range, does more for both range and protection than passive stretching does.
Do Nordic curls really work?
The evidence is unusually strong for a single exercise, with meta-analyses reporting roughly a halving of hamstring injury rates in squads that do them consistently.
The catch is adherence: they are uncomfortable, and the protective effect fades when teams stop doing them.
Why does my hamstring keep going?
Usually because the original injury was rehabbed to comfort rather than to capacity, leaving a strength deficit and changed muscle architecture that persist for months.
It responds well to a proper eccentric strength programme even a long time after the original injury.