Injury Case Study: The Hamstring

The Hamstrings group play a key role in knee joint flexion and hip extension and are involved in almost all of human movements; from walking to running, as well as many other physical activities. As a result, hamstring strain injuries are one of the most common muscular injuries.

It is thought that the occurrence of hamstring strain injuries is due to the combination of high forces with rapid muscle lengthening actions, as seen in high-speed running (30). In the late swing phase, the hamstrings rapidly change from acting eccentrically (decelerating the extended knee) to performing concentrically (supporting hip extension), which places them in a more susceptible elongated position under high mechanical stress. 90% of hamstring strain injuries are non-contact, which may in part be due to an ever-increasing metabolic demand of team sports combined with a higher proportion of matches spent running at high speed.

Assessing Hamstring Injuries & Rehab

Hamstring strain injuries are typically graded medically from Grade 1 to Grade 3. A Grade 1 diagnosis is usually a mild pull or strain, and pain typically lasts a few days. A Grade 3 tear, however, can take several months to recover from. Grade 1 tears are the most common and usually a sudden pain and tenderness is felt, and it is painful during movement. Severe Grade 3 tears are very painful and are normally accompanied by a popping-like sensation at the time of injury. The primary recovery strategy is to rest the leg and try to avoid taking big strides. Other strategies such as keeping the leg elevated and short periods of ice and compression may help speed up recovery. The real key is not returning to sport and training too early, and slowly building up running based activities once pain and tenderness has subsided. 

Risk Factors for Hamstring Injuries

There are a number of established risk factors for hamstring strain injuries. Some of these we cannot modify such as advancing age, with older players suffering from a greater risk of injury. Previous hamstring strain injury is also a major risk factor. The long head of the Biceps Femoris muscle has the highest risk of both injury and re-injury (32). Re-injury typically results in longer periods of recovery than first-time incidences, highlighting the need to improve current prevention and rehabilitation strategies to reduce initial and subsequent hamstring strain injuries.

Nordic Hamstring Curls 

Nordic Curl strength training has been proposed as a method to prevent hamstring strain injuries. The Nordic Curl is the most widely researched eccentric training exercise. Large- scale soccer Nordic Curl interventions have been reported to reduce both first-time occurring hamstring strain injuries and recurrent injuries making it an exercise of particular interest. The Nordic Curl is an eccentric only exercise, placing load on the hamstring muscles whilst they are lengthening, which produces proposed beneficial adaptations in eccentric strength and muscle architecture. 

With the Nordic Curl, it is important to gradually build up the number of repetitions and sets over time, starting with as few as 2-3 repetitions. As with any eccentric-based training, you can expect some DOMS after the first few sessions. The focus should be performing the contractions slowly and controlled throughout the movement with an emphasis on technique, trying to keep the hips square. Another consideration is that more recent evidence suggests similar adaptations and reduction in hamstring strain injury risk can be achieved with much lower training loads (2 sets of 4 rep’s). 

From a programming perspective, it is important to try and limit the number of Nordics in periods where there are lots of high-speed running or intense periods of match play to avoid unnecessary fatigue and increase injury risk, this should also be a consideration for coaches on when to programme Nordic Curl into an athletes’ training programme. The Nordic Curl is an eccentrically overloading exercise and therefore should be progressed by increasing the “active” range of motion you can achieve. 

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