Hamstring Strains: Why They Happen—and Why They Recur

A systematic review covering six field-based team sports found that hamstring injuries represented approximately 10% of all injuries. Injury incidence was also substantially higher during matches than during training, reflecting the greater speed and intensity of competition.

In elite Australian football, researchers examined 773 hamstring strains recorded over seven seasons. Each AFL club averaged approximately seven hamstring injuries per season, and around 72% of in-season injuries occurred during competitive games. The biceps femoris—the hamstring muscle on the outside of the posterior thigh—was involved in approximately 84% of cases.

Running-related movements accounted for 57.5% of the injuries for which a mechanism was reported, with acceleration the largest individual category. Kicking, jumping, landing and changing direction were also reported mechanisms. Hamstring strains are therefore not caused by one movement or one isolated risk factor. They generally occur when the demands placed on the muscle exceed its current capacity.

Community athletes face many of these same demands, particularly when weekly training contains limited exposure to sprinting but weekend matches require repeated maximal or near-maximal efforts.

The hamstring muscles make up almost half of all soft tissue injuries in sport.  Hamstring loading is particularly high during late swing phase of running, when the leg is moving forward and the muscles are active while lengthening to prepare the limb for ground contact.

Hamstring strains occur commonly cluster around high-speed activities when the athlete is sprinting & making sudden changes of pace.

A hamstring strain is not one diagnosis with one predictable recovery timeline. The prognosis can vary considerably depending on which muscle and tissue are involved.

Some injuries are largely confined to the muscle fibres or myotendinous junction. Others extend into the tendon or intramuscular connective tissue and may require a longer, more carefully progressed rehabilitation programme.

One example is the distal biceps femoris T-junction, where the muscle and tendon form a T- or fan-shaped arrangement. In a small 2026 study of professional footballers with MRI-confirmed injuries at this site, players with a longer T-junction configuration took an average of about 43 days to return to play, compared with 29 days for those with a shorter configuration.

Research in elite track-and-field athletes has also shown that some free tendon hamstring injuries can take substantially longer to recover than injuries limited to the myotendinous junction.

The practical message is simple: two athletes may report the same sudden, sharp pain at the back of the thigh but have very different injuries and recovery timelines. Clinical assessment is the starting point, with imaging considered when tendon involvement, a more complex injury or an unexpectedly slow recovery is suspected.

In the AFL study, recurrent injuries accounted for approximately 26% of all hamstring strains. Just over half of those recurrences occurred within two months of the preceding injury. Recurrent injuries also took approximately six days longer, on average, to return to play than first-time injuries.

Broader rehabilitation literature has reported that close to one-third of hamstring strains may recur, with the early period after return to sport presenting particular risk. Subsequent injuries may also be more severe than the original strain.

There is no single explanation for every recurrence. Possible contributors include:

• persistent hamstring weakness
• inadequate exposure to high-speed running
• incomplete recovery of sport-specific capacity
• altered movement strategies
• an inappropriate rehabilitation progression
• returning to full competition before tolerating the required training demands

Pain settling is therefore important, but it is not sufficient evidence that the athlete is ready to sprint, kick or compete at full intensity.

Early, appropriate loading rather than prolonged complete rest.

Current clinical guidelines recommend introducing hamstring strengthening—including eccentric exercise—early in rehabilitation, according to the athlete’s pain tolerance, injury severity and functional presentation. Rehabilitation should then progress through strengthening, trunk and pelvic control, running, acceleration and deceleration.

This does not mean aggressively loading every hamstring injury immediately. The starting point and rate of progression must match the specific injury.

Progressive strengthening through relevant muscle lengths and speeds.

Rehabilitation should restore the hamstring’s ability to produce and absorb force across the positions and contraction speeds required by the athlete’s sport. Eccentric strengthening is an important component, but it should form part of a broader program that also includes running progression and sport-specific conditioning.

Progressive exposure to high-speed running.

Jogging comfortably is not the same as being ready to sprint. Running exposure needs to progress through increasing speed, acceleration, deceleration and repeated efforts before the athlete returns to unrestricted competition.

Criteria-informed return to sport.

Return-to-sport decisions should not be based only on the number of weeks since injury. Assessment may include symptoms, range of motion, strength, functional testing, tolerance of high-speed running, training exposure and the athlete’s ability to complete sport-specific tasks.

There is no single universally accepted test or numerical threshold that guarantees an athlete will not experience another strain. Return-to-sport decisions therefore require a combination of objective testing, clinical reasoning and successful exposure to the demands of training.

Where the Nordic Hamstring Exercise Fits.

The Nordic hamstring exercise has strong evidence as part of injury-prevention programming. A systematic review and meta-analysis involving 8,459 athletes found an overall injury risk ratio of 0.49 for programs containing the Nordic exercise compared with programs that did not—an approximate halving of hamstring injury rates.

However, this evidence relates primarily to prevention programs. It does not mean that every athlete with a new hamstring strain should immediately begin full Nordic hamstring exercises. Exercise selection, dosage and progression need to match the stage and characteristics of the injury.

Why Rest Alone Is Usually Not Enough.

Reducing activity during the early stages may be necessary to control symptoms and protect the injury. However, rest alone does not restore eccentric strength, sprinting capacity or tolerance of repeated high-speed efforts.

An athlete can feel comfortable walking, cycling or jogging while still being inadequately prepared for maximal acceleration or sprinting. A structured rehabilitation program progressively closes that gap between being pain-free and being ready to compete.