Updated: Mar 16, 2020
Ask any new health professional or fitness coach what the hamstring group does and they will most likely tell you ´hamstrings flex the knee´. If they are a little more detailed they may add that ´hamstrings extend the hip´. And the thorough folks out there will proclaim ´hamstrings can assist in other activities such as rotating the femur or helping it abduct or adduct´. Wikipedia states the action of the hamstrings is to "flex the knee and extend the hip". Scrolling further down in the details Wikipedia does mention assistance in rotation as well as the hamstring group being important antagonists to knee extension.
But one super important function is most likely missing from the new doctor, therapist, or strength coaches response. Can you think of what function that would be?
Let us use another example to drive the point home before we reveal everything. Wikipedia describes the action of the serratus anterior (SA) as such: "protracts and stabilizes scapula, assists in upward rotation". This is certainly true...primarily during an open-chained activity. The SA will protract your scapula so you can throw a ball, shake someone's hand, or reach for the TV remote. However, it can also do something else...retract your rib cage. When you bench press your spine and rib cage is fairly stable and activating a SA will help you reach to lock-out and finish your lift. But what if we flip the stabilizer around. It is no longer a spine and rib cage stable on a bench, but rather hands and knees stable on the ground. Now if you fire the SA the ground will not allow you to reach unless you can press the earth away from you. What happens instead is you retract the rib cage up towards the sky. They may be two sides to the same coin, but those sides are not equivocal.
We could do this for every muscle in the body essentially. Pectoralis minors elevate ribs, but they also tilt scapulas. Scalenes externally rotate ribs and they can laterally flex necks. Lower traps depress and retract scapulas yet they can also assist in contralateral spinal rotation. And on and on...
So why can relentlessly stretching your hamstrings be causing you or your client harm?
Because hamstrings stabilize the pelvis. Hamstrings, among others, if balanced will control the forward rotation of the innominates and prevent hyperlordosis of the lumbar spine. Without sagittal hamstring control (or abdominal control), Janda´s Lower Crossed Syndrome will most likely become the reality. That control also allows the leverage of other keys muscles to ramp up. Have you ever noticed how terrible extremely hyperlordotic individuals are at basic physical therapy movements such as the dead bug? How about planks? Give them access to hamstrings and they may find it easier because with hamstring control, the abs (and glute max) gain leverage to support such a pelvic position. Have you noticed how poorly deep lumbar curved individuals breathe and handle cardiovascular exercises? Give them hamstring strength to maintain a neutral pelvis and the leverage to the diaphragm will most likely kick back in as a muscle of respiration and that person will start to perform better!
*The over-lengthened gluteus maximus will not be able to initiate restoration of view B in such an exaggerated position. This must first be mitigated and stabilized via the hamstring group to allow for Gmax leverage.
The catch-22 here is that a forward pelvis and deep lumbar curve will place eccentric tension on the hamstring musculature...therefore giving the patient the perception of "tight" hamstrings.
It is likely their problem is not the poor flexibility of the hamstrings, but rather poor posterior pelvic tilt ability due to long eccentrically oriented hamstrings.
The difficulty with these individuals is finding the other associated functional compensations in the body and deciding where and how to make the proper intervention with their rehabilitation program. Are their hamstrings the problem in isolation? Most likely not. Stay tuned for part II where we discuss and demonstrate strategies to remedy these issues.