Top 5 Fridays! 5 Ways to Measure Hamstring Flexibility - part 1 Assessment | Modern Manual Therapy Blog

Top 5 Fridays! 5 Ways to Measure Hamstring Flexibility - part 1 Assessment




In recent years, research has been conducted to understand the anatomical causes for reduced hamstring muscle extensibility and its relation to both altered lumbopelvic movements and hamstring muscle injury. Muscle shortness refers to the length of the individual sacrcomeres and their lengthening capacity. Muscle stiffness refers to the force required to effect the length of the connective tissue. These concepts focus directly on the structure of the muscle tissue and not on the neuromechanosensitivity of the neural tissues for which muscles provide a dynamic container. (Kuilart, Woollam, Barling, & Lucas, 2005; Marshall, Cashman, & Cheema, 2011)

The anatomical causes for reduced hamstring muscle length and perceived tightness is the focus of this blog, with the aim to understand if altered neurodynamics or connective tissue extensibility is the underlying cause of such tightness. This blog was posted originally on Rayner & Smale.

“Inability to extend the knee completely when the hip is flexed accompanied by discomfort or pain along the posterior thigh and/or knee is usually attributed to hamstring muscle tightness” (Mhatre, Singh, Tembhekar, & Mehta, 2013, p. 155). The hamstrings muscles are innervated by the sciatic nerve and also serve as a mechanical interface and container for the nerve. Therefore, both muscle tightness and altered neural tissue mobility can result in reduced knee extension range of movement and perceived muscle tightness. A study found that 84% of patients with posterior thigh pain during a slump test experienced a reduction in symptoms with cervical extension (Kuilar, et al., 2005). What this suggests is that perceived hamstring tightness may have more correlation to neural mechanosensitivity that reduced hamstring extensibility. It is therefore necessary "to differentiate between various anatomical structures because the treatment of altered neural tissue mobility is conceptually different from that of reduced hamstrings extensibility” (Mhatre, et al., 2013, p. 154).

There is a growing body of evidence that indicates that hamstring flexibility is a reflection of neural tissue mechanosensitivity and that tests which allow structural differentiation are best suited to indicate the cause of reduced mobility and direct treatment towards neurodynamic techniques which focus on restoring optimal neurodynamics. (Butler, 2005; Lai, Shih, Lin, Chen, & Ma, 2012; Shacklock, 2005)


1) Passive straight leg raise test (SLR)

When it comes to measuring hamstring flexibility, almost all research articles use the Passive Straight Leg Raise Test (SLR) to measure hamstring flexibility. This test is describe in detail by Shacklock (2005), who states that >80 degrees hip flexion is a normal test outcome. However, the SLR test does not measure hamstring muscle extensibility in isolation. Rather, it is a measure of muscle extensibility, neurodynamics and hip joint flexion range of movement.

The SLR test can be biased to differentiate more clearly between canal structures and peripheral nerves through structural bias, such as changing ankle dorsiflexion/plantarflexion, hip rotation/adduction/abduction, and cervical flexion. It is important to have a measure of the range of hip flexion at onset of symptoms, the location and description of the limiting factor and the effect that moving body parts distal/proximal to the hip has on the test outcome. From here it is easier to identify the role of neural mobility or muscle extensibility during the test.

Image: Passive straight leg raise test (Cleland, 2005, p. 175).


Maitland (2005) & Shacklock (2005) instruct the process of a slump test as:
  • Have the patient sit on the edge of the couch with the back of their knees touching the edge of the couch. Ask for resting pain/symptoms.
  • Instruct the patient to slump through their upper and lower back (without flexing the cervical spine) and the therapist applies a gentle over-pressure (not to end of range). A good instruction is to ask the patient to slump their shoulders to hips and drop straight down. Assess for any change of symptoms.
  • Instruct the patient to tuck their chin to chest as they look down and a firm overpressure is applied by the therapist to maintain cervical/thoracic/lumbar position. Assess for any change in symptoms.
  • Instruct the patient to extend their knee as far as possible and note the range of symptoms or pain response. Ask "Is that your pain?".
  • The end position is sustained while neck flexion is released and the change in pain response is noted. Also, if the patient is unable to achieve full knee extension, then once neck flexion is released, ask the patient to try extend their knee further.
  • Ankle dorsiflexion can be added before or after knee extension to increase the stretch and assist with structural differentiation.
  • If firmer over-pressure is required, repeat the test in long sitting.
  • Therapists should also decide, based on the patient history, if over-pressure is appropriate at all. "The therapist must take into account specific information, such as irritability, sensitivity, latency and contraindications" (Shacklock, 2005, p. 143).
Positive response: Both the increased knee extension range and reduction in symptoms with release of cervical flexion would implicate dural pain-sensitised structures over hamstring muscle extensibility, as the limiting factor to knee extension range of movement.

Normal response (Maitland, 2005; Shacklock, 2005):
  • Mid thoracic (T9/10) pain/discomfort during thoracic and lumbar flexion.
  • A pain free lack of 30 degrees of knee extension can be normal.
  • Stretching in the posterior thigh and knee, extending into the calf.
  • Ankle dorsiflexion increases the posterior thigh/knee pain.
  • Reduction of symptoms with release of cervical flexion.

Image: Slump test (Maitland, et al., 2005, p.146).


Subjects are positioned in supine and the hip is flexed to 90 degrees and stabilised. The therapist then passively extends the knee to the end of range, at which point, the knee flexion angle is measured. Their inter-rater reliability is reported to be 0.99 and some authors recommend the passive knee extensive test as the most reliable measure of hamstring length. (Davis, Quinn, Whiteman, Williams, & Young, 2008) Normative data is limited but a rough guide for males is a knee flexion angle of 38 degrees and females 28 degrees across all ages (Kuilart, et al., 2005).

Image: Passive knee extension test (Davis, Ashby, McCale, Mcquain, & Wine, 2005, p. 29). 


“Subjects were positioned in supine without a pillow underneath the head. The participant’s left hip was flexed and stabilised to 90 degrees by an assistant. They were then asked to slowly extend their left knee until they felt the first stretch sensation. They maintained this position till the knee flexion angle was measured with the goniometer” (Mhatre, et al., 2013, p. 156). Normative data suggests that a knee flexion angle of 40 degrees is the average range across ages and sexes (Kuilart, et al., 2005).

Image: Active knee extension test (Kuilart, et al., 2005, p. 92).


McHugh, Johnson, and Morrison (2012) established that when neural tension (thoracic and cervical flexion) is added to a hamstring stretch, the increased stretch sensation is not caused by contractile tissue response or increased EMG activity. The main changes in contractile response occur during the last 10 degrees of movement. Therefore neural tension is responsible for the increased stretch sensation during range. There results also demonstrated that when neural tension is increased during a hamstring stretch, there is likely to be a 9% decrease in range of movement in tolerable range with no difference in maximum stretch range. These authors were the first to demonstrate in vivo that “in the absence of significant contractile activity, an increased resistance to hamstring stretch in the neural tension position can be attributed to tensile force in the neural structures” (McHugh, et al., 2012, p. 167).

  • There are four main tests for measuring hamstring length.
  • Many of the tests are not interchangable and a range of tests should be used to accurately measure range of movement and its limiting factor.
  • Each test needs to be done in a reproducible manner.
  • It is important to ask "Is that your pain?"
  • Most of these tests allow for structural differentiation to explore neural tissue mobility and it's impact on the available range of movement.
  • Assessment of causes of posterior thigh pain/tightness requires a neurodynamic examination. 
The above tests have been well supported throughout the literature for their reliability and construct validity for the measurement of hamstring length and lower limb neurodynamics. Once the cause of reduced range and perceived tightness has been established, then treatment and exercises can be more specifically targeted to improve this deficit in range of movement.

The second part of this blog looks closer at the research comparing different treatments for improving ’perceived hamstring tightness’, the procedure for these techniques and their efficacy for improving hamstring flexibility and neurodynamics.


Sian Smale
 is an Australian-trained and APA-titled Musculoskeletal Physiotherapist. Sian has been writing a Physiotherapy evidence-based blog for the past 3 years called Rayner & Smale. Sian is based out of San Francisco and continues to write and teach Clinical Pilates while working towards her Californian Physical Therapy license. Sian has also created a free, online pregnancy and post-natal home-based workout program Hey Fit Mama.


Butler, D. S. (2005). The neurodynamic techniques: a definitive guide from the Noigroup team: Noi Group.

Cleland, J. (2005). Orthopaedic clinical examination: an evidence-­‐based approach for physical therapists: WB Saunders Co.

Davis, D. S., Ashby, P. E., McCale, K. L., Mcquain, J. A., & Wine, J. M. (2005). The Effectiveness of 3Stretching Techniques on Hamstring Flexibility Using Consistent Stretching Parameters. The Journal of Strength & Conditioning Research, 19(1), 27-­32.

Davis, D. S., Quinn, R. O., Whiteman, C. T., Williams, J. D., & Young, C. R. (2008). Concurrent validity of four clinical tests used to measure hamstring flexibility. The Journal of Strength & Conditioning Research, 22(2), 583-588.

Hengeveld, E., & Banks, K. (2005). Maitland's peripheral manipulation: Elsevier/Butterworth Heinemann.

Kuilart, K. E., Woollam, M., Barling, E., & Lucas, N. (2005). The active knee extension test and slump test in subjects with perceived hamstring tightness. International Journal of Osteopathic Medicine, 8(3), 89-97.

Lai, W. H., Shih, Y. F., Lin, P. L., Chen, W. Y., & Ma, H. L. (2012). Normal neurodynamic responses of the femoral slump test. Manual therapy, 17(2), 126-132.

McHugh, M. P., Johnson, C. D., & Morrison, R. H. (2012). The role of neural tension in hamstring flexibility. Scandinavian journal of medicine & science in sports, 22(2), 164-­169.

Shacklock, M. O. (2005). Clinical neurodynamics: a new system of musculoskeletal treatment: Elsevier Health Sciences.

Interested in live cases where I apply this approach and integrate it with pain science, manual therapy, repeated motions, IASTM, with emphasis on patient education? Check out Modern Manual Therapy!

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