Award Date


Degree Type

Professional Paper

Degree Name

Doctor of Physical Therapy (DPT)


Physical Therapy


Background and Purpose: Low back pain (LBP) is associated with paraspinal muscle dysfunctions. A method to study the deep lumbar paraspinal muscle activation is with intramuscular electromyography (EMG). However, it is currently unknown how paraspinal muscle performance is affected by the invasive intramuscular insertion and the presence of the fine-wire electrode in the muscle. The purpose of this study was to analyze how insertion of fine-wire EMG into lumbar paraspinal muscle affects the lumbar paraspinal muscle fatigue, endurance, activation, and peak extension torque during high exertion spinal extension exercises. Participants: 20 individuals between the ages of 18-40 participated. The participants were healthy with no history of LBP within the last 6 months that required activity modification or medical care. Methods: Data was obtained during 3 separate testing sessions, spaced 5 to 10 days apart. The first session obtained baseline outcome measures without intramuscular insertion (BL), with subsequent sessions utilizing a random order of insertion followed by leaving the intramuscular electrode fine-wire in (WI) or out (WO) of the muscle. Lumbar paraspinal peak extension torque was assessed with isokinetic dynamometry. Lumbar paraspinal endurance was evaluated using the Sorensen test. Paraspinal muscle fatigue was assessed using the rate of change (slope) of the median frequency during the endurance test. Percent of muscle activation was calculated by using the average muscle activation level during the endurance task. Pain and discomfort levels were recorded using the Visual Analog Scale (VAS) at specific times during the test sessions. All outcome measures were compared across the 3 conditions using one-way repeated measures ANOVAs and post-hoc analyses when indicated. Results: Our results showed no significant difference in peak torque (p = 0.196) between the BL, WI, and WO conditions. A significant difference in lumbar paraspinal endurance was found between the 3 conditions (p = 0.025). Post-hoc analysis showed that the muscle endurance in the WO condition was significantly longer than the BL condition (161.30 ± 58.267 sec vs. 142.05 ± 48.159 sec; p = 0.037). Percent of muscle activation during the endurance testing was not significantly different between the 3 conditions (p = 0.120). Pain scores reported during the 3 conditions were minimal (ranged 0-4/10). No pain was reported on the first day of testing (BL). No significant difference in pain scores was found between the WI and WO conditions: during each of the the three MVIC trials, after the MVIC trials, during the Sorensen test, or after the Sorensen test (p = 0.104, p = 0.186, p = 0.214, p = 0.330, p = 0.527, p = 0.481, respectively). Discussion: Our findings suggested that the insertion and presence of fine-wire EMG in the lumbar paraspinal muscles had no significant impact on lumbar paraspinal muscle peak extension torque, activation or fatigue and induced minimal pain. However, the results did suggest that the insertion and subsequent removal of the fine-wire did have an affect on lumbar paraspinal endurance. This study provides empirical evidence to validate the use of fine-wire EMG for studying lumbar paraspinal muscles during activities that require high muscular exertion.