Low back pain is a significant public health problem, is very prevalent, and is often
characterized by the persistence of symptoms. Unfortunately, substantial improvements in
people with chronic low back pain are rare, causing most people to live with the pain.
People with chronic low back pain may have an exaggerated pain response to nociceptive
input into tissues that may also cause symptoms distant from the site of the primary
symptoms. Historically, these symptoms were thought to be related to pathoanatomic
changes to the muscles, ligaments, or joints. However, the severity of these structural
changes weakly correlates with the clinical presentation and, in most cases, is not
directly related to diagnostic image findings. Patients with chronic musculoskeletal
pain, in general, show signs of local/central sensitization. The central sensitization
may appear to be directly correlated with the intensity and duration of pain. Therefore,
it is essential to reduce pain intensity and minimize the duration of pain to prevent
this from happening.
Pain relief for chronic low back pain patients should be aimed at treatments that reduce
central excitability and increase central inhibition. Research into chronic low back pain
treatment has demonstrated strong evidence that different types of exercise decrease pain
and improve quality of life. However, exercise itself may be painful, preventing a person
from exercising. Thus, treatments aimed at decreasing pain will improve a person's
ability to exercise and participate in activities of daily living.
One treatment aimed at reducing central excitability and increasing central inhibition is
transcutaneous electrical nerve stimulation (TENS). TENS is a "non-pharmacological"
treatment for pain that is inexpensive, safe, and easy to use. Prior studies show that
TENS utilizes opioid receptors both spinally and supraspinally to inhibit nociceptive
dorsal horn neurons, reduce excitatory neurotransmitter release, and reduce hyperalgesia.
Thus, TENS may be particularly useful in people with chronic low back pain because it can
activate descending inhibitory pathways (reduced in chronic low back pain patients) and
inhibit central excitability (increased in chronic low back pain patients).
Previous studies that have investigated the effects of TENS on pain in low back pain
patients have failed to use proper intensities of current, and the assessment of pain was
not performed during the peak of the analgesic response. Previous studies show inadequate
intensities do not reduce pain or increase pressure pain thresholds. Further, TENS
typically does not affect resting pain, while changes in pressure pain thresholds and
pain with movement are reduced. Thus, the current study proposes to assess the effects of
TENS on measures of pain, function, and descending inhibition using the maximal tolerable
intensity of TENS applied to a large area of the trunk.
