The hamstrings & low back pain
Low back pain (LBP) is extremely common, occurring in upwards of 80% of people at some point in their life. Hamstring “tightness” is often thought of as a contributing factor to LBP. This tightness is described as an inability to elongate a muscle or an actual shortening of the muscle. But in people with LBP, is this all that’s going on?
I am not saying that decreased flexibility in the hamstring muscles and fascia never contributes to LBP. In fact, when the hamstrings are tight they impact pelvic alignment creating muscle imbalances, restricted movement, postural asymmetries and ultimately LBP. The increased pull of the hamstrings on the pelvis and back can also cause restrictions and trigger points in the muscles and fascia and decreased ROM in joints. In fact, the entire posterior fascial line will be affected.
Let’s review some anatomy to better understand how the hamstrings can manually exert these forces. The hamstrings are comprised of three different muscles that are located in the back of your thigh. These muscles, the semimembranosus, semitendinosus and biceps femoris together form what we call the hamstrings. They attach to the ischial tuberosity (IT) or the “sit bone” at one end, and just below the knee at the other end. Tension in the hamstrings pulls downwards on the IT causing abnormal positioning of the pelvis and restricted movement of the pelvic joints. Because the lumbar spine essentially sits on the pelvis, it will pass its problems along to the low back.
But as I said at the beginning, that’s not all that is going on. “Muscles are stupid and they do what they are told” (Ulrik Sandstrom). What does this mean? It’s referring to the fact that the nervous system is in control, not your muscles. Our bodies are equipped with a protective mechanism called the stretch reflex. When a muscled is stretched this reflex increases electrical activity within the muscle causing it to contract in order to limit the extent of muscle lengthening to within a safe range. For example, when tension is placed on the hamstrings, ie when you bend over to pick up a box, as you reach the end of what your brain identifies as safe, the stretch reflex will be triggered. This elicits a feeling of “tightness” and controls how far you can bend over to pick up the box. In essence the nervous system is initiating a defense mechanism to protect your hamstring muscles. In people with LBP the reflex is triggered too early causing the electrical activity to rise far faster than in people who do not have LBP. Their hamstring muscles have a more sensitive stretch reflex and so a lower tolerance to being stretched. The muscles may appear “tight” and inflexible but they are actually being incorrectly instructed by the nervous system to contract. Remember, they are stupid and are just doing what they’ve been told.
Stretch Therapy (ST) and Soft Tissue Manipulation (STM) can help with both etiologies of hamstring related LBP. Hamstring “tightness” is often caused by restrictions and trigger points in the hamstring muscles, the muscles that rotate the hip and the hip flexors (antagonist muscles of the hamstrings). Other contributing factors include impaired hip joint ROM and adhesions in the fascia network. ST coupled with STM address all of these dysfunctions.
Repeated ST increases the hamstring’s stretch tolerance or the limit to which stretching can occur without pain or discomfort. As this tolerance improves and discomfort decreases the brain does not tell the muscle to contract as soon into the stretch as it previously did ie it delays the stretch reflex. The brain alters its perception of the safe range for the hamstring muscle to elongate allowing for a deepening of a stretch; getting more muscle, joint and fascial extension decreasing LBP.
Take-away: Hamstring muscle and facial restrictions as well as decreased stretch tolerance can contribute to LBP. ST and STM address these issues effectively decreasing LBP.
References
Halbertsma JPK, Goeken LN, Hof AL, et al. (2001). Extensibility and stiffness of the hamstrings in patients with nonspecific low back pain. Arch Phys Med Rehabilitation. 2001; 82: 232-8.
Kalyan B. Bhattacharyya. The stretch reflex and the contributions of C David Marsden. Annuals of Indian Academy of Neurology.2017.
Roberta Y W Law 1 , Lisa A Harvey, Michael K Nicholas, et al. Stretch exercises increase tolerance to stretch in patients with chronic musculoskeletal pain: a randomized controlled trial. Physical Therapy. 2009 Oct;89(10):1016-26
Halbertsma JPK , Goeken LNH. Stretching exercises: effect on passive extensibility and stiffness in short hamstrings of healthy subjects. Arch Phys Med Rehabil. 1994;75:976–981.
Magnusson SP , Simonsen EB, Aagaard P, et al. . A mechanism for altered flexibility in human skeletal muscle. J Appl Physiol. 1996;497:291–298.
Phil Page, PT, PhD, ATC, CSCS, FACSM. Current concepts in muscle stretching for exercise and rehabilitation. International Journal of Sports Physical Therapy. 2012 Feb; 7(1): 109–119.
