RESUMEN
To define the dynamic organization of the neuromuscular system, we need useful tools that allow for the expression of the neuromuscular system in low dimensional term [i.e one variable], so it seems that relative phase provides a better measure of organization of the neuromuscular system. Besides, selection of a measure for research or clinical use should be motivated by several factors, including the measure reliability. To our knowledge there seems to exist no study that have ever investigated the reliability of the relative phase and deviation phase in healthy or Low back pain subjects in dynamic movement tasks. Twelve healthy volunteers and 12 low back pain patients performed repeated trunk bending motion in eight different conditions of high and low speed, in symmetric and asymmetric planes, with or without external load. All measurements were repeated on a second session, 7-10 days later. Mean absolute relative phase and deviation phase of lumbar-thorax and pelvis-lumbar were used to calculate coordination pattern and variability. Relative reliability was assessed using intra class correlation coefficient [ICC] and absolute reliability was assessed using standard error measurement, minimum detectable change and coefficient of variation. Results in healthy subjects revealed that relative phase and deviation phase showed good to excellent reliability, with ICC range of 5.3-8.4 and in low back pain group ICC range was0 /52-0/85 except in three asymmetric test conditions and one symmetric test condition. SEM values range for healthy subjects were 0/92-4/8 and for low back patients were 1/2-5/8. Relative phase and deviation phase are suggested as good parameter to use for evaluating coordination and variability in dynamic situations such as lifting and complex trunk movement and also for discrimination low back pain patients from healthy subjects.
RESUMEN
The theraputic exercise is regarded as one of the most important theraputic interventions in the chronic low back pain patients. Stabilization exercise is among the most significant practical ones in these patients. The study of the effects of these exercises on the variability of trunk muscles postural strategies and the ability in normalizing these strategies are among the uncertainties that have remained unknown up to the present time. The purpose of this research is the study of the effect of stabilization exercises on the variability of postural control strategies in these patients. The study was performed on 21 [14 males, 7 females] recurrent non-specific low back pain patients. The electromyographic activity of Deltoid, Transverse Abdominis/Internal Oblique, External Oblique and Erector Spinae muscles of each person was recorded in 75 rapid arm flexion with maximum acceleration. Then, 14 individuals were placed in the experimental group and 7 in the control group randomly. The experimental group performed isolated abdominal hollowing and bracing exercises using pressure biofeedback with the supervision of a physiotherapist in different positions including supine, sitting on a chair, standing still and standing with rapid arm raises with maximum acceleration once a day, for 20 sessions. The variables studied in this research were evaluated in both experimental and control groups after the training sessions. The standard deviation of the trunk muscles onset latencies relative to deltoid muscle was statistically analyzed by a dependent t-test in both groups. The results revealed that performing the stabilization exercises increases the variability of the timing of anticipatory postural adjustments in TrA/IO in the experimental group [P=.037], while there were no significant changes in the variability of EO [P=.0346] and ES [P=.673] muscles in these patients. The variability of the timing of the anticipatory postural adjustment in TrA/IO [P=.199], EO [P=.702] and ES [P=.465] muscles did not show any significant changes in the control group. The study of the results showed that the reduction in the variability of postural control system in recurrent non-specific low back pain patients as a factor that causes the continuity of back pain can be improved by goal-directed stabilization exercises