Spine Position and Neural Sensitivity

The purpose of this research study is to see if there is a relationship between the tightness of the hamstring muscles (muscles on the back of the thighs), reported sensations related to stretch of the nerves of the lower extremity, and different positions of participants' backs. We will investigate the qualitative differences as provided verbally by participants (sensation felt at maximum knee extension angle) and quantitative differences as provided by surface electromyographic (EMG) measurements of hamstring activity and inclinometer measures of the knee angle.

The Slump Test, introduced by Maitland in 1978, has been a clinical staple for determining adverse neural tension or altered neurodynamics and neurosensitivity related to intradiscal derangement or stenotic narrowing of the lumbar spine. The slump test is a highly reliable, common clinical tool used to assess neural tissue mechanosensitivity in patients with both spinal and lower limb pain. However, it is unclear if the slump test can be used to differentiate between those with true adverse neural tension compared to those with neurosensitivity due to compression of the neuroforaminal interface. The positioning of the slump test places maximal tension on the neural tissues both caudally and cranially, either reducing knee extension angle (KEA) in the affected side as opposed to the unaffected side, provoking radicular symptoms, or both. Hall's research found that there was mechanical activity in the hamstring muscles that came on with neural tension testing. This finding can be used to objectively assess when a participant is at their peak tolerable limit of neural tension in specific trunk positions during the slump test. Observation and clinical experience suggest there may be a subset of individuals who have increased neural tension in the slump test during spinal extension (shortening of the nerves) as opposed to flexion (stretch of the nerves). To date, there has been little research that has objectively demonstrated how trunk position affects neural tension during the slump test. Our research aims to determine if there is a difference in patient reported symptoms and hamstring activity between trunk flexion and extension during the slump test with healthy, younger individuals with no recent history of low back pain (LBP) or related symptoms. We expect to find a difference in range of motion (ROM), symptoms, and hamstring activity when the slump test is done in spinal flexion as opposed to spinal extension. This research will help to establish the prevalence of greater sensitivity in the extended vs flexed posture and establish a normative set of symptoms as described by healthy individuals.

Knee Extension Angle (KEA): This test will be administered with an ankle-foot orthosis (AFO) maintaining the participants ankle in neutral. The participant will lie supine on the examination table with the contralateral lower extremity (LE) stabilized on the support surface using a mobilization strap. The hip of the lower being examined will be flexed to 90 degrees. The participant will then actively straighten their lower leg while maintaining upper leg in same position Once the participant feels they are at maximal knee extension (patient instructed to straighten leg as far as what is comfortable), the angle will be measured with iPhone Inclinometer. Participant asked to report any symptoms they are feeling and where (recorded for qualitative analysis)

Straight Leg Raise (SLR): Position the participant in supine on the plinth with knees extended and L LE strapped to the plinth The participant will keep the AFO donned on the R distal ankle to keep the ankle in neutral position. A researcher will passively lift the participant's right leg moving at a slow but consistent pace of approximately 15 degrees per second, while keeping it straight until a significant resistance is detected or the participant reports a production of symptoms, whichever occurs first. Measurement of the SLR angle will be assessed with iPhone inclinometer. Participant asked to report any symptoms they are feeling and where (recorded for qualitative analysis)

Slump Test Procedure: Participant will be instructed to sit upright with their legs over the edge of table AFO remains on R leg Participant will sequentially flex trunk, look down at the floor Participant will extend R knee until symptoms are felt. Measure of angle with iPhone inclinometer placed at superior aspect of medial malleolus Participant asked to report any symptoms they are feeling and where (recorded for qualitative analysis)

Extended Slump Procedure: Participant will be instructed to sit upright with their legs over the edge of table AFO remains on R leg Participant is asked to arch their lower back into maximal extension in sitting, stabilized to research bench to maintain hyper-lordosis posture. The participant is asked first flex cervical spine, then to extend their knee until it reaches full ROM or symptoms are felt that limit ROM. Knee extension ROM is assessed with iPhone inclinometer at superior aspect of medial malleolus. Participant asked to report any symptoms they are feeling and where (recorded for qualitative analysis)

A measurement of the degree of knee extension achieved during the KEA, Slump, and extended slump tests

surface EMG activity of the biceps femoris during KEA, SLR, slump, and extended slump referenced to hamstring maximal voluntary isometric contraction

for each test, the most distal extent of symptoms and intensity on the 11 point numeric pain rating scale will be collected. Participants will be asked to describe the nature of the symptoms experienced during the test (e.g. stretch, pain, pull, tingle, etc)

Inclusion Criteria: healthy individuals between the ages of 18 and 65 without low back pain. Exclusion Criteria: Known previous diagnoses of sciatica or disc herniation Diagnosis of scoliosis History of pain in the low back or back of the leg History of back surgeries Any recent hamstring injuries Any recent fractures History of osteoporosis Have feeling of pins and needles down the leg Have a known nervous system disorder Have a known systemic inflammatory condition Have Rheumatoid Arthritis Known history of cardiovascular issues Have a known connective tissue disorder Bowel/bladder issues Are or may be pregnant Type 1 or type 2 diabetes mellitus Active/history of cancer Allergy to adhesives Are actively involved in a lawsuit regarding personal bodily injury or receiving workman's compensation Currently taking/have recently taken antibiotics known as fluoroquinolones (ie. Cipro, Levaquin, Noroxin)