Meet your Muscles: Hamstrings

Our hamstrings are an incredibly important part of our posterior chain. Since we live in a forward facing world (not to many of us are walking around backwards), our posterior muscles are not used often or properly. The hamstrings are made up of three muscles, similar to the quadriceps. While the 2 muscle groups work opposite each other; they are both large enough to be multi-joint movers.  Without proper functioning hamstrings, you may not get to enjoy walking, running and jumping. Often these muscles are either too tight and short OR too long and weak.

The Anatomy


When our trunk “fixed” and isn’t moving, the semitendinosus muscle extends the hip, but also flexes the knee and rotates it in. It is superficial (closer to the skin) and lies on the inside of the back of the thigh.


The semimembranosus muscle lies deeper and more on the inside (medial) of the back of the thigh. It moves the hip and the knee in the same way as it’s “sister” muscle.

Bicep Femoris (long head and short head)

This muscle has 2 parts; the long head and the short head. The long head of the Bicep Femoris extends the hip as we begin walking. It attaches to the Fibula, which is the outer portion of the lower leg. Because of where it inserts it flexes the knee and moves it outwardly.  The short head of the Bicep Femoris more specifically helps with knee flexion and outward rotation, it does not help in hip extension.

What is the injury and how does it happen?

Like all muscles, the hamstrings are susceptible to strains. The are various grades of strain from a grade 1 strain, which is mild; to a grade 3 strain, which is a complete tear of the muscle. A complete tear could potentially take months to heal. You can also injure the tendons in a similar fashion. Typically, if the hamstrings are injured it is in the central muscle belly or close to the tendons. In severe injuries, the tendon can be completely torn and a piece of bone can break away with it, this is known as an avulsion fracture.

Injury to the hamstrings happens when the muscle is overloaded. This occurs when the hamstring is lengthened or stretched to its maximum and then there is a sudden load with movement that challenges it.

Use sprinting as an example, with the force of your weight hitting the ground and then the movement to extend your hip, a muscle strain can happen.  There are risk factors to injuring your hamstrings such as muscle tightness or weakness, muscle imbalance or poor conditioning.


  • Sudden sharp pain in the back of your thigh
  • Swelling within the first few hours of injury
  • Bruising or discolouration at the pain site
  • Muscle weakness


There are many different exercises to help strengthen your hamstrings, but first, determining if you need strengthening or stretching is key. You may be surprised by what you hear from your trainer or therapist.

We have a great lower body workout video that will help strengthen those hamstrings. Matt Rice, a Registered Physiotherapist, explains the importance of each of the exercises. So you know what it’s working and why.