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Background and aim:The role of thoraco-lumbar muscles is important in spinal column stability. Following fatigue due to constant activity, these muscles encounter with variable control pattern and variations of median and mean frequencies are little in relation to torque of force. However these parameters are useful in the literatures, but due to complexity of neuromuscular interaction and variety of motor control, signal processing can determine a wide range of changes and measurements.     

Signal processing nonlinear techniques exploit in biologic signals. Variables of nonlinear techniques are recurrence, determinism, entropy and so on.

The purpose of this study was to determine changes of entropy as nonlinear parameter in comparison with linear parameter and applicability of entropic measurements of the erector spinae muscles during fatigue.   

Materials and methods: Ten healthy women and 6 women with nonspecific low back pain (NSLBP) with a range of 20-30 years old patticipated in this study. Surface electromyography of isometric activities recorded from trunk (T12), lumbar (L3) and biceps femoris muscles during modified Sorenson isometric fatigue test. Median and mean frequency and also nonlinear parameters such as entropy and trend measured in one second of muscles activities before and onset of fatigue. 

Results:  Following fatigue in healthy group, median and mean frequencies reduced at a range of 12-20% (p<0.05). This decrement in LBP group was little (4 - 20%, p<0.05). Entropy increased 120-200% and trend reduced 800-2000% in normal subjects (p<0.05), whereas subjects with LBP indicated increment of entropy 65-220% and decrement of trend 240-500% (p<0.05). Before and after fatigue there was a significance difference between two groups in entropy parameter (p<0.05), whereas median and mean frequencies differences were not significant.

Conclusion:Following static positions, fatigue occurred in three levels of above muscles particularly at lumbar region. Traditional fatigue indicators showed good differences, but percentage of variability was low in comparison to nonlinear parameters. It suggests that nonlinear variables especially entropy are more sensitive than traditional indicators and can explain these stochastic behaviors

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Background and aim: The presence of the flexion relaxation phenomenon (FRP) during trunk flexion represents myoelectric  silence consistent with increased load sharing of the posterior discoligamentous passive structures. A number of studies have shown differences in the FRP between patients with chronic low back pain and healthy individuals, Persistent activation of the lumbar erector spinae musculature among patients with back pain may represent the body's attempt to stabilize injured spinal structures via reflexogenic ligamentomuscular activation for protecting them from further injury and avoiding pain.

Materials and methods: Two groups of female subjects ((20 - 40 years old) were participated in this study. First group consisted of 10 subjects with chronic low back pain (CLBP) and second group consisted of 10 healthy ones as control group. Both groups have performed 5 cycles of trunk flexion - extension . The speed of the movement repetition controlled by an electronic metronome . The EMG signals recorded from T12 and L3 paravertebral muscles and bisepse femoris on the right side. The lumbar flexion motion degree has been measured by the digital flexible goniometry.  All subjects have done Sorenson Back Endurance test in prone laying position. The subjects have extended their trunk up to the horizontal position and sustained in this position up to fatigue level .The subjects leave the table and asked to do 5 more cycle of trunk flexion - extension.

Results:  In patients group there is an increment and significant differences in lumbar flexion degree at the time of muscle EMG off  in comparison with healthy subjects after fatigue test (p<0.05). In both groups, the myoelectric silence period showed a significant change with respect to the pre- fatigue (p<0.05). The median frequencies shifted to lower frequencies after fatigue protocol (p<0.05).

Conclusion: Muscle reflexive responses would change following fatigue protocol. Therefore, the muscle activity will increase after the fatigue period. In the other hand, in patient group the role of the muscles as a stabilizer seems to be increased to enhance the stability at the injured segment after fatigue protocol .This protects the segment against pain and disability.

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Background and aim: Proprioception is a main component of somatosensory system that plays a protective role in acute injuries through reflex muscular splinting. Proprioception reduction could be a source of deficits in reaction time, postural control and postural stability. In chronic low back pain  patients (CLBP) the proprioception is decreased and leads to dysfunction in motor control and increased the risk of injury. Evaluation the repositioning of lumbar region could be an indication to measure the lumbar proprioception . The purpose of this study was to compare the lumbar repositioning in CLBP and healthy females. 

Material and Methods: Eighteen CLBP (22.83 ± 2.93 years) and 18 healthy females (23.33 ± 2.19 years) participated in this study. Lumbar repositioning error in 30% and 60% of lumbar full flexion and neutral position with closed eye in standing was evaluated with electrogoniometer. Absolute and constant error for 3 repositioning points were obtained and analyzed.

Results: Absolute error in patients with low back pain was significantly higher than control subjects in all 3 position points (P<0.05). Constant error did not show significant difference between two groups. (P>0.05)

Conclusion: Increased in absolute error of females with CLBP in lumbar repositioning implies that some aspects of proprioception may lose in patients with CLBP.

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Background and Aim: Some of the patients with chronic low back pain commonly do not experience full recovery with the conventional physical therapy. It is revealed that may be there are some items in subjects with low back, which are not studied well till now. Since there are some evidences about breathing pattern disorder in low back pain patients, the purpose of this study was to compare between some important breathing pattern index in non-specific chronic low back pain and healthy subjects .

  

Materials and Methods : In this descriptive analysis study, there were 16 patients with chronic non-specific low back pain and 16 healthy subjects. Both groups were matched and selected by some of the demographic characteristics. Respiratory data including respiratory rate, volumetric, time depended and chemical index were calculated by K4b2 instrument.

  

Results: They have significant differences in some of the respiratory parameters including respiratory rate, inspiration and expiration times and total time of respiration between two groups, whereas inspiration total time ratio, volumetric and chemical index do not have significant differences.

  

Conclusion: Existence of disorders in some parameters of respiratory patterns in patients with low back pain are revealed that survey of respiratory system in patients with chronic non-specific low back pain can be effective in diagnosis and treatment process in physiotherapy centers.

  

Keywords: Low back pain, Breathing, Respiratory chemistry.

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Background and Aim: Low back pain (LBP) is the most common and expensive musculoskeletal problem in industrialized societies. One in ten people suffers from LBP once in his life. It is self-limited up to 90%, but it is common to repeat. By the way, sacroiliac joint (SIJ) is the origin of low back and pelvic pain in many cases and one of the most important elements in normal musculoskeletal function during gait cycle. Muscles are important to stabilize this joint plus to bones and ligaments. Some of the muscles (Gluteus Maximus, Biceps Femoris, Multi Fidus, Erector Spinae) contributing in gait cycle are important to transfer load through SIJ. The aim of this present study is to compare muscle activity timing during initial and mid stance phase of gait cycle.

  

Methods and Materials: Sixteen low back pain cases and fifteen healthy subjects participated in this study. A footswitch is placed beneath foot at the suffered side in LBP cases and dominant foot in control group. Two markers were on the 5^th metatarsal bone and lateral maleolus. Electrodes are placed on selected muscles according to SENIAM. Digital camera and EMG Datalink were turned on simultaneously and subject started to walk with his own favorite speed in a specific direction and path. Onset and time to peak of selected muscles were recorded during gait by Datalink and processed by its software.

  

Results: Low back pain cases showed delayed muscle onset, although it was not significant (P=0.4). Time to peak of all selected muscles in loading response event in LBP group was longer and significant (P=0.01). There was also significant difference in time to peak of all selected muscles during mid-stance event (P= 0.005) except biceps femoris muscle.

  

Conclusion: Delayed onset and longer time to peak during initial and mid stance phase of gait can be interpreted as a compensatory strategy to control trunk movements effectively, provide sufficient stability and transfer load to lumbar area efficiently.

  

Key words: Muscle activity, Low back pain, Gait, Trunk muscles, Lower Limb Muscles

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Background and Aim: Regarding to high prevalence of low back pain (LBP) in athletes and its effect on their athletic function, an accurate evaluation before planning the rehabilitation program seems necessary in athletes with LBP. It should be considered that human movements are like as a kinetic chain. It means that any problems in every parts of this chain can cause dysfunction in the other parts of the chain. Not taking attention to the relationships between different parts of this chain may result in suboptimal rehabilitation. Therefore, focusing treatment on the entire parts of the kinetic chain besides the injured part, may prevent recurrenceof the dysfunction. Since in the kinetic chain hip muscles act as a link between lower extremities and trunk, the purpose of the present study was to evaluate and compare muscles strength of hip joint in female athletes with and without non-specific chronic LBP.

  

Materials and Methods: Fifteen healthy female athletes and 15 female athletes with non-specific chronic LBP participated in this study. Their age was between 18-30 years. Hip extension, abduction and external rotation strength in all participants were measured. A hand-held dynamometer (HHD) was used to measure muscle strength. Since fixing HHD by examiner’s hand is fraught with error, it is fixed by a stable frame.

  

Results: The maximum strength value of hip extension and abduction in female athletes with LBP were significantly lower than these measures in healthy group (P < 0.05). No significant differences were seen in the maximum value of hip external rotation strength between two groups (P > 0.05).

  

Conclusion: The results of the present study show that hip extension and abduction strength in female athletes with LBP were lower than these measures in healthy group. Therefore, hip strength measurements besides the examination of the spinal column seem to be necessary in evaluation and rehabilitation of the patients with LBP.

  

Key Words: Non-Specific Chronic Low Back Pain, Hip Muscles Strength, Athlete

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Background and Aim: Low back pain (LBP) is the most common and expensive musculoskeletal problem in industrialized societies. One in ten people suffers from LBP once in his life. It is self-limited up to 90%, but it is common to repeat. By the way, sacroiliac joint (SIJ) is the origin of low back and pelvic pain in many cases and one of the most important elements in normal musculoskeletal function during gait cycle. Muscles are important to stabilize this joint plus to bones and ligaments. Some of the muscles (Gluteus Maximus, Biceps Femoris, Multi Fidus, Erector Spinae) contributing in gait cycle are important to transfer load through SIJ. The aim of this present study is to compare muscle activity timing during initial and mid stance phase of gait cycle.

  

Methods and Materials: Sixteen low back pain cases and fifteen healthy subjects participated in this study. A footswitch is placed beneath foot at the suffered side in LBP cases and dominant foot in control group. Two markers were on the 5^th metatarsal bone and lateral maleolus. Electrodes are placed on selected muscles according to SENIAM. Digital camera and EMG Datalink were turned on simultaneously and subject started to walk with his own favorite speed in a specific direction and path. Onset and time to peak of selected muscles were recorded during gait by Datalink and processed by its software.

  

Results: Low back pain cases showed delayed muscle onset, although it was not significant (P=0.4). Time to peak of all selected muscles in loading response event in LBP group was longer and significant (P=0.01). There was also significant difference in time to peak of all selected muscles during mid-stance event (P= 0.005) except biceps femoris muscle.

  

Conclusion: Delayed onset and longer time to peak during initial and mid stance phase of gait can be interpreted as a compensatory strategy to control trunk movements effectively, provide sufficient stability and transfer load to lumbar area efficiently.

  

Key words: Muscle activity, Low back pain, Gait, Trunk muscles, Lower Limb Muscles

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Background and Aim : Chronic non-specific low back pain is one of the important health problem in military and different factors have been reported in its emergence. The aim of this study is to determine the association between low back pain and education level, Body Mass Index (BMI), exercise, smoking status ,work status and bad postures in military men.

  

Materials and Methods : In this non-experimental case-control study, 92 subjects (mean age= 29.16 year, SD= 8.55 year) with chronic non-specific low back pain and 93 subjects (mean age= 26.80 year, SD=9.22 year) without low back pain were selected by simple non-probability method from military centers in Tehran. Evaluation tools of this study included a self-administrated questionnaire, weighting scale and metal tape measure.

  

Results : According to the results of bivariate logistic regression, risk factors of exercise (P= 0.003), smoking status (P= 0.042), grade of BMI (P= 0.034), bad posture grades including heavy objects lifting movements (P= 0.007), bending movements (P= 0.003), rotating movements from the lumbar (P= 0.011), carrying bulky objects (P= 0.034), carrying heavy objects (P= 0.05) and working in squatting position (P= 0.005) had a significant association with low back pain. Job status (P= 0.999), education level (P= 0.056) and bad postures grades movements like wringing clothes (P= 0.958) had not a significant association with low back pain.

  

Conclusion : Doing regular exercise and having normal BMI decrease the risk of suffering from low back pain in the military while smoking and doing injurious physical activities during work (lifting heavy objects, bending movements and rotating from the lumbar, carrying bulky and heavy objects, and working in squatting position for a long time) increase the risk of suffering from low back pain.

  

Key Words : Chronic non-specific low back pain, Military forces, Biomechanical risk factors, Exercise

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Background and Aim: Low back pain is the most common and most costly musculoskeletal disorder among nurses. The studies have showed that ergonomic risk factors are the main cause of back injury. Our aim in this study is to evaluate the incidence of low back pain in nurses with participating in manual handling of patients and determination of its relationship with ergonomic risk level of inpatient wards in a subspecialty hospital in Tehran.

Materials and Methods: Thirty nurses who were active in manual handling of patients, (aged between 25to43), participated in this study. The Nordic standard questionnaire and Slump clinical test were used for evaluation of low back pain and pressure on the nerve root, respectively. MAPO (Movement and Assistance of Hospital Patients) quantitative index was used for evaluating the ergonomic risk level of manual handling of patients in 16 sectors of a hospital including 174 wards.

Results: The results showed that ergonomic risk level was high. Ninety percents of evaluated wards were in red band. Based on results of Nordic questionnaire, %66.7 of nurses had experienced back pain in the past 12 months. Based on the results, 46.7% of  nurses who were active in sectors with high ergonomic risk have been suffering of back pain in the past 12 months and 53.3% of theirs slump test were positive. The Chi-Square test confirmed that there is a significant relationship between low back pain prevalence and risk level from the MAPO index in parts. (p=0.004)

Conclusion:  Findings from this study showed that there was a relationship between ergonomic conditions of hospital’s sectors with back pain in nurses. Therefore, it is expected to improve ergonomic conditions particularly supply of adequate human resources, supply of auxiliary equipments for patient transmission, repairs timely and implementation of reforms constructive is associated with reduced incidence of back pain in nurses.

Key words: Ergonomic risk level, MAPO index, Slump clinical test, Low back pain, Nurses.