The ball reaches the back of ruck. The scrum-half passes the ball into the centres, who carry it, taking the play wider and creating a two-on-one for the winger. A burst of speed will see a try scored. Receiving the ball, the winger accelerates, surely about to score – but pulls up! Clutching the back of his thigh, limping, unable to continue. The commentator, experienced fans and sports medicine professionals come to the same conclusion – a hamstring tear.
Hamstring injuries are one of the most prevalent in sports involving high-speed running like football, rugby, field hockey and track running. They also effect everyday people, from over-exuberant boot camp attendees, fathers reigniting old rivalries at their child’s school sports day or physiotherapists charging up hills having become bored of long slow runs (yours truly). But what are the hamstrings, why do they get injured sprinting and what is important in rehabilitating these injuries and why?
Many people recognise tightness in the back of their thighs as representing hamstring tightness. The hamstrings are a group of four muscles travelling from the pelvis to knee and push the thigh back and bend the knee when contracting to shorten – what is called concentrically. Two of the hamstrings attach to the inside of the knee, called the semimembranosus and semitendinosus, and the other two on the outside are the long head and short head of biceps femoris. The most commonly injured during faster running and sprinting is the long head of biceps femoris. Injury severity varies in size of injury and what structure – peripheral muscle/fascia, the join between muscle and tendon or the tendon itself – is injured, but I won’t discuss the implications today.
Our gait, or how we walk, run and sprint, is divided into two phases – stance and swing. It seems logical for our hamstrings to be injured during stance when our foot is in contact with the floor and our hamstrings are pushing our leg backwards. After all, this is when our winger clutched his thigh and pulled up instead of scoring. In reality, it seems most likely the hamstrings are injured when swinging the leg, just before our foot comes in contact with the ground.
As the swing leg moves forward, the hamstrings contract to slow down the leg and prepare to position it on the ground for our next step. They also lengthen during this movement, which represents an eccentric contraction. Studies have found the point just before contacting the ground is when the most force is required from the hamstrings and is also when the hamstrings are longest and lengthening fastest. The force and lengthening required from the hamstrings both increase as we run faster – the knee comes higher up to the chest and foot reaches further out faster as we swing. High forces at long muscle lengths at high speeds are why these injuries occur when sprinting, and at the very end of swinging our leg. The long head of biceps femoris attachment to the pelvis means it lengthens more and is consequently susceptible to injury during sprinting.
Almost all patient’s think their hamstrings are tight. Hamstring injury occurrence while lengthening could suggest stretching is key to prevention and rehabilitation. Although this may help mitigate some hamstring injuries it isn’t the main problem. It doesn’t regain or improve the strength of the muscle or specific function of the hamstrings during sprinting. Of bigger concern is how much force the hamstrings exert while lengthening, or their eccentric strength. High levels of eccentric strength seem protective of hamstring injuries and exercises focussing on this cause favourable changes in the muscle, namely lengthening smaller parts of muscles called fascicles. This improves the strength of the hamstrings at long lengths – the point at which they are injured during sprinting. Regaining eccentric hamstring strength in movements and positions similar to sprinting should therefore be a key component of rehabilitation from hamstring injuries, though different facets specific to each patient and their injury should always be considered.
Once pain and swelling settles after the initial hamstring injury, suitable exercises might include sliding leg curls, stiff leg deadlifts and Nordic hamstring exercises. All should be performed with slow lengthening of the hamstrings or with one leg while lengthening and two while shortening to bias the eccentric contraction. Training like this might seem risky, as hamstrings are injured while lengthening, but slow controlled movements rarely cause muscle injuries and heavy resistance is often not required due to the extra challenge provided by slowing the movement down. Injured hamstrings will likely be weaker than expected, however, so you should consult your physiotherapist to be assessed and diagnosed accurately and be prescribed the right exercises. They will also be able to prescribe running and sprinting drills and faster exercises once you are ready, as these will be required to ensure your hamstring is ready for sprinting or your chosen sport.
The two biggest risk factors for hamstring injury are being older and having had a hamstring injury before, neither of which you can change, so proper rehabilitation is important. Improving your hamstring strength, especially eccentric strength, will return you to what you want and need to do and reduce your risk of recurring injury. Less time wasted means less strength lost and therefore getting back to your sport or training as quick as possible. If you think you have injured your hamstrings, contact and have an assessment with a physiotherapist quickly to get started on the right exercises early.
If you’d like some expert advice or treatment for a hamstring injury feel free to get in touch, or call us on 0207 937 1628.
Specialist Sports and Musculoskeletal Physiotherapist.