Hamstring strain

A sudden pain in the back of your thigh while sprinting. You may have suffered a hamstring strain, one of the most common muscle injuries among athletes. This injury accounts for 37% of muscle injuries in professional soccer and affects both amateur and professional athletes.

Good news: with the right treatment and proper rehabilitation, the vast majority of hamstring strains heal completely. Here's what you need to know to recover well.

What is a Hamstring Strain?

A hamstring strain is a tear in the muscle fibers at the back of the thigh, affecting one or more of the three muscles that make up this group: the biceps femoris, semitendinosus, and semimembranosus.

The hamstrings are made up of three distinct muscles. The biceps femoris is located on the outer side of the thigh, while the semitendinosus and semimembranosus are on the inner side.

The biceps femoris is the most frequently affected, accounting for 53% of hamstring injuries. These injuries typically occur at the musculotendinous junction, where the muscle meets the tendon.

The hamstrings play an essential role: they bend the knee, extend the hip, and stabilize the pelvis during running.

What Causes a Hamstring Strain?

A strain occurs during a powerful eccentric contraction, typically during the acceleration phase of a sprint, when the muscle lengthens while contracting to slow down the leg's movement.

The critical moment is just before the foot touches the ground during a sprint, specifically during the late swing phase. Contrary to popular belief, the risk is highest not at maximum speed, but during maximum acceleration.

A meta-analysis published in the British Journal of Sports Medicine identifies the following risk factors:

Fatigue at the end of a game significantly increases the risk. This is why injuries are more frequent in the second half.

Several factors increase the risk of a hamstring strain: older age, a previous hamstring injury, limited flexibility, and fatigue.

Hamstring strains are particularly common in sports that involve sprinting and rapid changes of direction, such as track and field, soccer, American football, and dance.

Who is at Risk of a Hamstring Strain?

Athletes who have previously suffered a hamstring strain are at the highest risk of re-injury. A significant proportion of hamstring strains recur within the first year after returning to sports, and the recurrence is often more severe than the initial injury.

The incidence in professional soccer ranges from 0.87 to 1.8 injuries per 1000 hours of play. Players who have previously suffered a hamstring strain are particularly vulnerable.

Recurrence is often more severe than the initial injury. This is why complete rehabilitation before returning to sport is essential.

How to Recognize the Symptoms of a Hamstring Strain?

The main symptom is sudden, localized pain in the back of the thigh, sometimes accompanied by a popping sensation at the moment of injury.

• Palpation of a specific tender spot on the back of the thigh
• Active Knee Extension Test: Pain-Induced Limitation
• Passive Stretch Test: Pain During Muscle Elongation
• Isometric Strength Test: Weakness and Pain

• Complete inability to put weight on the leg
• Extensive bruising extending towards the knee
• Palpable depression in the muscle (suggests a tear)
• Persistent severe pain even at rest

What are the different grades of severity?

Hamstring strains are classified into four grades based on the extent of tissue damage, ranging from simple pain with no visible injury to a complete muscle tear.

The British Athletics Muscle Injury classification distinguishes these grades:

A minor injury (Grade 1) generally heals faster than a moderate injury (Grade 2). The actual healing time varies greatly from person to person, depending on the location of the injury and the response to rehabilitation.

The grades describe the extent of the injury: Grade 1 is a small injury involving a few fibers, Grade 2 is a moderate injury, and Grade 3 is an extensive injury that may even result in a tear.

Ultrasound is often used as an initial test because it is quick and inexpensive; MRI provides the most detailed images. The reliability of ultrasound depends largely on the experience of the person interpreting the results.

Two factors worsen the prognosis: a proximal location (near the buttock) and tendon involvement rather than muscle involvement.

How to treat a hamstring strain?

Treatment is based on the PEACE and LOVE protocol, a modern approach that replaces the older RICE protocol and promotes optimal tissue healing.

The Nordic hamstring exercise reduces the risk of injury by 51% and speeds up recovery. Askling's L protocol allows for a faster return to sport compared to conventional approaches.

• One of the criteria for returning to sports at full intensity is regaining at least 90% of the strength in the injured limb compared to the healthy side, with a full range of motion and without pain.
• No pain upon palpation
• Successful completion of functional tests (jumps, accelerations, decelerations)
• Confidence that I can get back in the game

How long does recovery take?

Recovery time varies greatly from person to person. The time it takes for a person to walk without pain helps predict when they can return to sports. A previous injury, on the other hand, increases the risk of a relapse. These factors should be part of the clinical evaluation.

Rehabilitation takes place in several stages: a rest period during the first few days, followed by active rehabilitation with gradual progression once the acute pain has subsided, and then a return to sports based on functional criteria. The duration of each stage depends on the individual’s response, not on a fixed schedule.

In professional soccer, a hamstring injury can keep a player out of the game for a variable period of time. Returning to the sport too soon increases the risk of a recurrence.

Return to sport should be guided by achieving objective criteria, not by a fixed timeline. This approach significantly reduces the risk of recurrence.

How to prevent recurrence?

Prevention relies on eccentric hamstring strengthening, an appropriate dynamic warm-up, and smart management of training load. Eccentric hamstring strengthening, such as the Nordic walk, helps reduce the risk of injury.

Static stretching before exercise has no clear effect on injury prevention.

• Maintain a hamstring/quadriceps strength ratio greater than 0.6
• Monitor your fatigue (rating of perceived exertion scale, sleep quality)
• Do not neglect pre-season training to develop eccentric strength
• Avoid sudden increases in training volume or intensity

Key takeaways

• Hamstring strains are common but treatable injuries
• A history of injury is the main risk factor for re-injury
• The PEACE and LOVE protocol guides modern treatment
• Returning to sport should be based on objective criteria, not a fixed timeline
• The Nordic hamstring exercise reduces injury risk by 51%