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A novel method of recording intersegmental spine kinematics was developed. The method was required to: (1) have similar accuracy and precision as current methods that record gross spine kinematics; (2) be reasonably insensitive to errors associated with marker detection or misplacement; and (3) be reasonably insensitive to skin movement artefacts. Four healthy participants performed trunk flexion, lateral bending, and axial twist movements; data were collected using the intersegmental method as well as electromagnetic sensors. Comparing methods, gross angular kinematic differences were within 1 SD during flexion and lateral bend, while axial twist resulted in the largest differences. To test sensitivity to marker error, random error was added to marker positions. The most proximal and distal intersegmental units were the most sensitive to marker error. Adding additional markers at the ends or interpolating padded markers reduced this sensitivity. The influence of skin movement artefact was investigated by digitizing locations of the skin with respect to the spinous processes in both neutral and fully flexed postures. In the lumbar region, large skin artefacts had minimal effect on intersegmental angles. The greatest strength of this method is the ability to dynamically record intersegmental spine kinematics.

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The purpose of the current work was to (1) determine whether low back cutaneous sensitivity could be reduced through the use of a topical lidocaine-prilocaine anesthetic (EMLA(®)) to mirror reductions reported in chronic lower back pain (CLBP) patients, as well as to (2) identify whether reductions in cutaneous sensitivity resulted in decreased lumbar spine proprioception, neuromuscular control and dynamic stability. Twenty-eight healthy participants were divided equally into matched EMLA and PLACEBO treatment groups. Groups completed cutaneous minimum monofilament and two-point discrimination (TPD) threshold tests, as well as tests of sagittal and axial lumbar spine active repositioning error, seated balance and repeated lifting dynamic stability. These tests were administered both before and after the application of an EMLA or PLACEBO treatment. Results show that low back minimum monofilament and TPD thresholds were significantly increased within the EMLA group. Skin sensitivity remained unchanged in the PLACEBO group. In the EMLA group, decreases in low back cutaneous sensitivity had minimal effect on low back proprioception (active sagittal and axial repositioning) and dynamic stability (seated balance and repeated lifting). These findings demonstrate that treating the skin of the low back with an EMLA anesthetic can effectively decrease the cutaneous sensitivity of low back region. Further, these decreases in peripheral cutaneous sensitivity are similar in magnitude to those reported in CLBP patients. Within this healthy population, decreased cutaneous sensitivity of the low back region has minimal influence on active lumbar spine proprioception, neuromuscular control and dynamic stability.

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