By Robert Frost PhD, A.T.
Lateral Hamstrings – Biceps femoris, long and short head
Medial Hamstrings – Semitendinosus, Semimembranosus
The Hamstrings extend along the back of the thigh. They connect the ilium to the lower leg. They traverse both the knee and the thigh joints. The Hamstrings flex the knee. They also extend and adduct the thigh. The medial Hamstrings medially rotate the thigh. The lateral Hamstrings laterally rotate both the knee and the thigh.
Both the medial and lateral Hamstring muscles have double innervation. The nerve branch at the proximal end extends the hip. Nerves at the distal end flex the knee. These two separate functions of the same group of muscles are independent. Using the same muscles, you can either flex your knee, extend your hip or both.
If the thigh is fixed, the Hamstrings provide posterior stability to the pelvis and extend the pelvis on the hips.
Reflex points for Hamstrings
The anterior neurolymphatic point for the Hamstrings is above the inner trochanter of the thigh. The posterior neurolymphatic point is the dimple between L5 and the PSIS. The neurovascular point is one inch above the Lambda – the posterior fontanelle. Hamstrings are associated with the Large Intestine meridian. The sedation point for the Large Intestine meridian, LI2, is located on the radial side of the index finger where the crease divides finger from palm.
Organ association: Rectum
Nerve supply: For the medial Hamstrings: sciatic nerve tibial branch, L4, L5, S1, S2
For the lateral Hamstrings short head: sciatic nerve peroneal branch, L5, S1, S2
For the lateral Hamstrings long head: sciatic nerve tibial branch, L5 S1, S2, S3
The Hamstrings are usually tested as a group. If there are knee problems, it is important to independently test the medial and the lateral Hamstrings too.
The subject lies prone and bends the lower leg about 60° up from the table. The examiner presses down upon the belly of the muscle to supply stabilization and keep the muscle from cramping during the test. The hips must remain on the table. For the group test, press straight down. For the medial hamstrings, laterally rotate the lower leg outwards. Press the leg down and out laterally. For the lateral hamstrings, medially rotate the lower leg inwards. Press the leg down and in medially.
When testing the medial Hamstrings, feel the belly of both the medial and lateral Hamstrings. Adjust your angle of attack so that the medial is active and the lateral is not. When testing the lateral Hamstrings, check that they are tightening and that the medial Hamstrings are not.
If cramping is not a problem, the Hamstrings make a useful indicator muscle when the subject is prone.
A photo of a hamstring test is on the following page.
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