Hamstrings

The hamstrings are a group of voluntary, skeletal muscles which are mainly responsible for knee flexion. However, these muscles are also involved in hip and knee movements during walking, squatting, climbing the stairs, tilting of the pelvis as well as various other leg movements.

The hamstring muscles are located in the back of the thigh, originating from the pelvis and femur, and inserting to the knee. The muscles that make up the hamstrings are the:

i. Biceps femoris, a long muscle located on the outer part of the back of the thigh. It allows hip extension, and knee flexion and knee lateral rotation. This muscle consists of a long head and a short head which attaches at the ischial tuberosity of the pelvis and the femur, respectively. They both insert to the fibular head.

ii. Semimembranosus, the largest of the hamstrings, is located more on the inner part of the back of the thigh. It too allows hip extension and knee flexion, as well as medial rotation of the knee. This muscle originates from the ischial tuberosity of the pelvis and inserts to the tibia.

iii. Semitendinosus, the longest of the hamstrings, is located between the biceps femoris and semimembranosus at the back of the thigh. It allows hip extension, as well as knee flexion and knee medial rotation. This muscle originates from the ischial tuberosity of the pelvis and inserts to the tibia.

Muscle strain and contusion constitutes two major forms of muscular injuries. A muscle strain occurs when the muscle is overstretched or torn. It is usually as a result of overuse, fatigue or improper use of a muscle. Muscle strains are described in three grades:

1. Grade I: Minimal muscular disruption and rapid return to normal function;
2. Grade II: A partial rupture of a muscle is present, with pain and some loss of function;
3. Grade III: Complete tissue rupture is observed, with pain, muscular retraction and functional disability.

The hamstrings are the most affected by this type of injury.

A muscle contusion is the direct consequence of direct trauma to the muscle, as in contact sports. It is characterised by pain, swelling, stiffness and restricted range-of-motion. While a muscle contusion can affect any muscle, it is more common in the quadriceps and gastrocnemius. To summarise, hamstring muscle injuries are common and can be mild to severe depending on the injury mechanism.

For people who take part in sports activities that require a lot of sprinting, such as, rugby, track or football, the long head of the biceps femoris is most commonly injured. However, the reason for this is not yet completely understood. It is theorised that it is because this muscle is activated more than the other hamstrings muscles during sprinting. In contrast, semimembranosus injury is more common in dancers and people who kick a lot, as these activities require extreme hip flexion and knee extension.

Nevertheless, the hamstrings can also become tightened when it has to compensate for the actions of other muscles which has weakened. A classic example of this would be lower cross syndrome, in which there is an imbalance of muscle strength of the muscles around the pelvis. Prolonged sitting – a common occurrence in the modern world can give rise to this. When the short, thick and powerful gluteus maximus becomes weak, it becomes less able to act as the primary hip extensor, so more load is placed on the longer and slender hamstrings which causes them to be overworked and damaged, leading to tightness. If not cared for, it may develop into a tendinopathy with time.

For the hamstrings, prevention of injury is better than cure. The best way would be to warm up your muscles before a sport or any strenuous activities, and stretching them out after the workout. There also a number of ways that the hamstrings can be stretched and strengthened, but that has to be tailored to each individual patient according to their needs by a healthcare professional. In the case of hamstrings tightness relating to muscle imbalances, lifestyle changes and a suitable exercise programme has to be implemented to help restore function and reduce disability.

Below is one type of hamstrings stretching exercise that you can try at home. Regardless, if you are suffering from long-standing hamstrings pain, be sure to consult a healthcare professional for a more detailed assessment and individualised treatment plan.