Comparison of muscle fatigue effect on electromyographic onset latency of trapezius muscle in posterior - anterior perturbation between patients with chronic neck pain and healthy persons

Fatigue process in patients with neck pain was happened more quickly than healthy persons and neck muscle fatigue increased body sway during standing, but there is less evidence about the behavior of these muscles in dynamic conditions such as external perturbation, so this study was done to investigate the effect of muscle fatigue on onset latency of upper trapezius muscle in posterior-anterior perturbation among patients with chronic neck pain and healthy individuals. In this quasi experimental and interventional study 16 patients with chronic neck pain [intervention group] and 16 healthy individuals [control group] were selected by simple and convenient sampling and based on inclusive and exclusive criteria. Data collection was done by using questionnaire and doing some tests and the main equipments were dynamometer, accelerometer and surface electromyography. The weight equal to 30% of maximum voluntary contraction used to produce fatigue process and 10% of body weight used to produce perturbation. Independent T test, Paired T test and Repeated ANOVA were used for data analysis. There was significant difference in onset latency of upper Trapezius muscle in posterior - anterior perturbation between two groups, before [P=0.006] and after [P=0.026] fatigue. This means that the onset latency was increased in healthy individuals and decreased in patients after fatigue. Also, there was significant difference in onset latency of Trapezius muscle in posterior - anterior perturbation between before and after fatigue in patients group [P<0.001] and healthy persons group [P=0.04]. Pain can change the onset latency of trapezius muscle and possibly it can decrease muscle activity in deep muscle and change the pattern of muscle activation. Fatigue as an exaggerated risk factor can decrease onset latency of superficial muscle in patients with chronic neck pain to stabilize the system, that it can increase the risk of injury

Comparison of electromyographic responses of superficial neck muscles in patients with chronic neck pain and healthy subjects during posterior - anterior perturbation

Several studies have reported significant disturbances in vertical posture during various standing and walking conditions, but there is little evidence about the behavior of related muscles in dynamic conditions such as external perturbation, so this study was done to investigate and to compare the delay in response of upper trapezius and sternocleidomastoid muscles as two superficial muscles in the neck area, in posterior-anterior perturbation among patients with chronic neck pain and healthy subjects. This study was a case-control study with simple nonprobable sampling. 32 subjects [16 healthy subjects and 16 patients with chronic neck pain] participated the study. Data collection was done using questionnaire and test performance. The equipments included dynamometer, chronometer and surface kinesiology electromyography. Dropping the weight equal to 10% of total body weight, performed using electrical magnet, followed by pulling of the trunk inducing perturbation was performed. There were significant statistical differences in response onset of upper trapezius [p=0.032] and sternocleidomastoid [p=0.012] muscles between two groups. This meant the response onset in patients was longer than healthy subjects. Pain can change the onset of response of trapezius and sternocleidomastoid muscles and possibly decrease muscle activity in deep muscles and change the pattern of muscle activation and possibly it can increase the risk of injury in patients with chronic neck pain

[Analysis of lumbar spine and hip pattern motion while stoop lifting in subjects with and without a history of low back pain]

Reports of pattern motion between lumbar spine and hip vary for stoop, loading conditions or the pathology present, such as chronic back pain. Therefore, the purpose of this study was to compare the relative contribution of the hip joint and lumbar spine during stoop lifting in subjects with and without a history of low back pain. This clinical trial was performed in Tehran. Fifty subjects were assigned as either a low back pain group or a control group. A Three-Dimensional Optoelectric Motion Analysis System was used to measure the amount of lumbar spine and hip motion during stoop lifting. Each subject performed stoop lifting with and without weight. The data were analyzed using independent t-test and repeated measurement test. These results showed that there were significant differences between patients with low back pain and healthy subjects in the pattern of motion [P<0.05]. Individuals with a history of low back pain tended to move According to the findings, history of backache can affect the change of pattern motion for hip joint and lumbar spine. This change may be a reason for the recurrent incidence of backache