"My hamstrings are tight, I can't touch my toes, that is why i have back pain." "My hamstrings are so tight, that is why I tore my hamstring."
There is much debate about the role of hamstring flexibility and its importance in hamstring injury, sports performance, and back pain. In this blog we will look at how you can measure your own hamstring flexibility, and also look at the evidence for whether tight hamstrings are important for injury and pain.
How can I check my hamstring flexibility?
We use 2 main tests to assess the flexibility of the hamstring, and these are also used to assess improvements in hamstring flexibility when following a stretch program.
1. The Straight Leg Raise test (SLR)
Actually this test measures the flexibility of more than just the hamstrings. It assesses the flexibility of all the tissues that run from the hip down to the feet,
(which is known as the fascia, and also the connective tissue that lines the sciatic nerve). However for simplicity, this is often referred to as a hamstring flexibility test. We would generally consider a normal SLR range to be from 75 to 95 degrees, although there is a lot of normal variability in this.
2. The Popliteal Angle test
As this test is performed with the knee bent, it more accurately measures the flexibility of the hamstring muscle itself. Hold the thigh with your hands so it is vertical so that the hip is at a 90 degree angle. Then straighten the knee as much as possible. The angle at the knee is what we are then interested in. We consider a normal range to be between 160 and 180 degrees of knee angle.
If these tests are very restricted in you, AND you feel it restricts your comfortable movement or sport related movements, then it is time to start a stretching routine.
But does Hamstring tightness matter?
Hamstring injury is one of the most common leg injuries in sports people and runners. It accounts for 13-15% of injuries in a wide range of sports. (1) As a result, there is a lot of research into understanding what makes a hamstring prone to injury.
In Movement
Hamstring tightness (SLR) will have an impact on the way you bend your back when you reach to your toes. Those with tighter hamstrings have been shown to have increased flexion/bending in their upper back (thoracic spine) when they lean forwards, and have reduced forward rotation of their pelvis, impacting motion in the spine (2).
In injury prevention
This is a hotly debated topic. Some studies have shown that tight ligaments and muscles are related to lower limb sporting injury in men college athletes. (3). Others have found the toe touch test not to be predictive of injury in the hamstring. Another study of Australian Rules footballers concluded that "It appears that a high bilateral hamstring stiffness and leg stiffness may be a determinant in the risk of sustaining a hamstring injury." (4).
In Sports performance.
Researchers have found that football players with more flexible hamstrings performed better in terms of sprint score, vertical jump, agility, and kicking speed (5).
A review of 23 research studies found that regular stretching improves force, jump height, and speed in sport. However an acute bout of stretching does not improve force or jump height, and the results for running speed are contradictory. (6). This suggests that a regular program of stretching is beneficial, however strong stretching just before sports performance is not indicated.
So what do we know about hamstring tightness?
Clearly, elasticity within the hamstring has been found to enhance performance and may decrease risk for injury. Although there are mixed results in the research, there is some evidence that supports the regular stretching of the hamstring muscle group, with the aim of gaining and maintaining an optimal muscle length.
So go ahead and test your flexibility with the tests above, and see if you can improve your flexibility tests with regular stretching. It may well make you move and perform better.
If you need help with your tight hamstrings, do get in touch for more advice.
1. J Sports Med. 2014; doi: 10.1155/2014/127471
2. Science & SportsVolume 25, Issue 4, September 2010, Pages 188-193
3. AMPR November 1996 Volume 77, Issue 11, Pages 1139–1143
4. AJSM Volume: 38 issue: 10, page(s): 2058-2064
5. Journal of Sports Sciences Volume 33, 2015 - Issue 12: Science and Medicine in Football
6. Clin.J.SpMed September 2004 - Volume 14 - Issue 5Does Stretching Improve Performance?: A Systematic and Critical Review of the Literature