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Background and Aim: In this study, we investigated : 1) The effect of diferent lengths of Abd. policis brevis muscle on variations EMG frequency spectrum. 2) The effect of muscle contractions on frequency spectrum and 3) The effect of different lengths of muscle on local muscle fatigue.

Material and Method: 20 normal subjects participated in this study. (with range of 20 - 34 years old). Each test carried out in four steps. Every person performed 3 minutes of isometric contraction in Abd. policis brevis muscle and EMG signals were saved for 5 seconds before and after the test. Then the  same procedure was performed while individual did 6 minutes free dynamic contraction and 6 minutes high speed dynamic contraction and 6 minutes forceful dynamic contraction respectively.

Results:This study showed that when the individual performed muscle contraction in short length, median and mean frequency increased (P = % 0) and fatigue test caused a decrease in frequency charactristics that was more in dynamic contractions in compare with isometric contraction (it was more obvious in forceful dynamic contraction). These parameters didn't change in different lengths (P = %9, P = %4, P= %3 for 0 - 45, 0 -90 and 45 - 90 degrees respectively).

Conclusion and discussion:This study showed that different muscle lengths and muscle contractions affect on frequency spectrum and it also showed the effect of different muscle lengths and muscle contractions on local muscle fatigue.

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Background and Aim: Several stretching methods have been shown to increase flexibility of the short muscles. Previous research suggests muscle energy techniques produce increments in range of motion, but there are many variations of muscle energy techniques. The purpose of our study was to determine the efficacy of muscle energy techniques with 50% of maximal voluntary isometric contraction and 10 second hold in compared to control group.

Materials and methods: A sample of 30 female subjects (aged 20 -25 years) participated in this study. All subjects had limited hamstrings flexibility in degrees of passive knee extension. The subjects in experimental group (n=15) received 3 muscle energy techniques (50% MVIC, hold time=10 sec) for 4 weeks, whereas the control group (n=15) remained without treatment. Before and after range of knee extension was measured for all subjects.

Results: The paired t test revealed a significant differences in flexibility for experimental group (P<0.001). There was no significant difference in flexibility gains in control group (P<0.001). Treatment group had significant greater flexibility than the control group (P<0.001).

Conclusion: Muscle energy techniques with above protocol produce an increase of hamstring flexibility.

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Background and Aim: Sports such as baseball, volleyball, and racquet sports demand skills that place substantial load upon the athlete's shoulder when his or her arm is in an overhead or abducted position. Athletes who participate in these sports are consequently at higher risk for overuse injuries of the shoulder. Infraspinatus syndrome is defined as a condition of frequently painless atrophy of the infraspinatus muscle caused by suprascapular nerve neuropathy. The syndrome typically causes symptoms that mimic those of rotator cuff tendinopathy, and the diagnosis is often overlooked until the condition fails to respond to a traditional rotator cuff treatment program.

In this study muscle timing and activities of shoulder rotator cuff compared between normal athletics and volleyball players with infraspinatus syndrome.

Materials and Methods: Thirty voluntary male professional volleyball players (20 healthy and 10 patient) in the range of 20 -30 years contributed in this study. Patients group in base of electroneurography had injury of suprascapular nerve at right side. Subjects lied prone on table and their shoulder were 90 degree of abduction and medial rotation with 90 degree of flexion in elbow with vertically position of forearm at the lateral side of table. Electromyographic activities of maximum voluntary contraction of infraspinatus, middle trapezius and teres minor . Muscles were recorded three times with monitoring of dynamometer for normalization of dynamic activities. Activities (RMS) of above muscles were recorded during three dynamic motions similar to spark skill and onsets of their activities determined by external synchronized apparatus.

Results: There was significant difference between normalized RMS of infraspinatus,. and middle trapezius of patients in dynamic motion (p<0.05). Whereas healthy subjects showed significant difference between infraspinatus. and two other muscles (p<0.05). Comparison of normalized RMS indicated different in all three muscles between two groups (p<0.05).  

The sequence of onset three muscle activities were different between two groups significantly (p<0.05). This sequence in patients was middle trapezius, teres minor and infraspinatus whereas in healthy subjects was middle trapezius, infraspinatus and teres minor. Duration of above muscle activities were different in two groups (P<0.05). In patients infraspinatus were active less than other two muscles.       

Conclusion: Professional volleyball players are candidate of suprascapular nerve and infraspinatus muscle weakness. Synergic and stabilizer muscles after this condition with more activities contribute and caused reduce of accuracy of motion and early muscle fatigue.

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Background and aim: Cryotherapy has long been introduced as a common method for preventing and reducing edema caused by traumatic injuries. Many studies have been conducted regarding other effects of cold such as its effects on muscle strength which provided controversial results over the past decades. The aim of this study is to investigate whether cold is capable of changing the muscle strength.

Materials and methods: The research was conducted on 30 volunteers with the mean age of 22 years. In a standard situation, the volunteers were asked to make their maximum grip force. Cold was applied over their anterior forearm using an ice pack for 15 minutes. The maximum grip force was measured before and within 1 to 120 minutes after cold application.

Results:The strength of the anterior forearm muscles decreased rapidly after cold application. The maximum reduction of muscle strength, in average 18% was observed after 10 minutes. This was followed by a gradual increase of grip force. After 120 minutes the force was increased to about 5% above the baseline force that was before cold application.

Conclusion: Regarding the slight increase in the muscle strength and its long delay, cryotherapy of muscles cannot be considered as a practical method in rehabilitation of patients. However, this method would be of great importance for athletes.

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Background and aim:The knee joint is one of the most important joints of human body, witch tolerates many forces while the subject is standing up or walking especially during close chain and squat positions.

Muscle fatigue may causes some modifications on effects of forces and accordingly some changes on strategy of movement, therefore the concentration in thigh muscles impression on continuous movements is a guidance that makes the investigation on these changes so important.

Materials and Methods: Fifteen healthy women in the range of 20-30 years were contributed in this study. Muscle fatigue were applied in separate sessions by maximal voluntary contraction (MVC) in both open and close chains.

Subjects were done five dynamic repetitions of flexion / extension motion of knee before and after fatigue tests. Surface electromyography (sEMG) recorded from vastus medialis (VM), rectus femoris (RF) and vastus lateralis (VL) muscles during all conditions of tests. Normalized electromyography (NEMG) of muscles activities in two conditions of concentric (Con) and eccentric (Ecc), also median frequency (MF) were calculated for fatigue index. Muscle timing or recruitment pattern indicated by onset of muscle activities for both dynamics chains.

Results:  There are significant different of fatigue indexes between before and after fatigue tests (p<0.05).  After fatigue muscle timing delayed in open chain (p<0.05) and recruitment patterns changed from VL- VM- RF to VL-RF-VM. Fatigue test in close chain caused increment of muscle timing (p<0.05), but it did not change recruitment patterns.

Conclusion: After fatigue tests MF reduced little than NEMG. Significant difference occurred in muscle timing. These variations were increase and delay of timing with change of recruitment in open chain. These findings suggest that motor control strategy is will change at different condirions of with and without load situations.

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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: With respect to attachment and mechanical relationship of hamstring and calf muscles, interaction between their function is unavoidable. Inspite of prevalence of hamstring and calf muscles shortness, there is not any statistical data about the relationship of shortness of above-mentioned muscles in Iran. The aim of this study was to verify of this prevalence.

Materials and methods: In this study 3308 healthy girls with age 3-17 years old participated. Length of calf muscles with dorsi flexion angle and hamstring with hip flexion angle (SLR) in both side were measured.

Results: The prevalence of hamstring and calf muscles shortness with together was20% in right and 25% in left side .The Prevalence of hamstring and calf muscles shortness with together in 20 district was greater than 3.The greatest amount was seen in secondary school(31.6%).               

Conclusion:The results indicated that most of subjects who had hamstring shortness, they had also calf muscles shortness, so if there is any shortness in one of them, we shouhd pay attention to shortness of the another.

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Background and aim: Muscle flexibility is an important component of physical fitness and injury prevention.

Passive Stretch can be effective in lengthening and making hamstring more flexible. Popliteal angle measurement is one of the most simple method in studying the efficiency of these methods however, in goniometry measurement, there is not any data about muscle tension and any proper judgment about flexibility.  The goal of this study is to evaluate length and stiffness of the hamstrings by Quick Release Movement before and after the passive stretch.

Materials and methods:14 men (20-30 years old) with shorted hamstring (20 degree or more ext lack in passive knee ext test by popliteal angle measurement) participated in this study. Before and after exercises, popliteal angle  and muscle stiffness  were evaluated with digital goniometer and  Quick Release Movement technique respectively. Evaluation of stiffness was performed in flexion and extension positions.

Results: A significant increase in hamstring length was observed. (P<0.05) There was decrease in stiffness in both position of flex and ext but it was significant when in extension state.(P<0.05)

Conclusion: Findings of this study demonstrate passive stretch's effectiveness in increase muscle length and lessening muscle stiffness. In addition Quick Release Movement can be a suitable method for measuring muscle stiffness.

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Background and aim: The function of deep neck flexor muscles is very important in physiotherapy assessments. The purpose of this study was to examine the reliability of sphygmomanometer device to measure the strength of deep neck  muscles.

Materials and methods: Thirty healthy non-athlete females aged 18-24 years old voluntarily participated in this study. The maximal contraction of deep neck muscles were measured in different times, different days and by two different testers using a sphygmomanometer device. At each session subjects performed three maximum voluntary contractions and the maximum strength was chosen for data analysis. The Interclass Correlation of Coefficient (ICC), Pearson product moment and CV% were used to assess the reliability of different measurements between times, days and two different examiners.

Results: The results of ICC, Pearson product moment and CV% indicated that the strength measurement of cervical stabilizer muscles were highly repeatable between different times, days and testers (ICC ≥ 0.90, CV% ≤ %3.8 and r ≥ 0.91).

Conclusion: The sphygmomanometer and the method which was used in this study appeared to be a reliable and useful method to measure the force of deep neck flexor muscles. It can also be suitable for the assessment of physiotherapy or rehabilitation programs.

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Background and aim: Active straight leg raise test in patients with sacroiliac joint dysfunction (SIJ ) is accompanied by feeling pain on joint or heaviness and inability to lift the leg. This test has been advocated as reliable and valid test for the quality of load transfer through the lumbo-pelvic region. With respect to the important role of muscles, in pelvic stability and with respect to patients with SIJ dysfunction can not do this test easily. There is no study has been done about assessment and comparison  of changes in muscle timing of pelvic stabilizer muscles and duration of ramping time during ASLR between healthy and patients with SIJ dysfunction 

Materials and methods:Eleven female subjects with clinical diagnosis of sacroiliac joint pain and 15 match healthy female subjects were tested in the supine resting position with the ASLR. Surface electromyography of rectus abdominus , oblique externus , oblique internus  , adductor longus , biceps femoris , gluteus maximus and  erector spine muscles  were recorded during ASLR test. Timing of muscles and ramp time during ASLR  test were acquired and measured in MATLAB software . 

Results: No statistically significance were found in ramp time between two groups. The onset timing of activation of adductor longus (A.L) was delayed on symptomatic side in subject with SIJ pain (P=0.006).

Conclusion: Delayed onset of A.L suggests an alteration in strategy for lumbopelvic stabilization that may disrupt load transfer through the pelvis.

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Background and aim: The shoulder area is the most complex region of the body and inherently unstable that motions are produced and controlled by sequenced activation of muscles in force couple patterns. It seems that investigating of shoulder muscle activation pattern is essential in the various tasks in healthy subjects due to the unstable structure of the shoulder and vital role of muscles in the stability. In order to evaluate motor control changes in the various movement, designing the therapeutic programs suitable to the shoulder pain and to evaluate effects of physiotherapy and preventing of side effects, this study was conducted. Up to now, it has not been evaluated in the D1flex & D1ext patterns yet.

Materials and methods: Thirteen female healthy volunteers participated in the experiment. Dependent variables of muscle activation such as onset and offset as well as sequencing of muscles (upper trapezius, lower trapezius, serratus anterior, pectoralis major, anterior deltoid and posterior deltoid) of dominant side were calculated during D1flex & D1ext patterns by surface EMG and Data log software in the standing position with speed movement of 25 degree/second.

Results: Special patterns of muscle activation were observed during D1flex & D1ext. Sequencing of muscle activation was different in the both movement patterns. Also, significant differences were found in the latency time of all muscles (p<0.05) except upper fibers of trapezius related to flex/ext goniometer (p=0.33) between both movement patterns.

Conclusion: This study demonstrated that there are special patterns of activation of muscles around the scapulohumeral articulation in the normal subjects. Rehabilitation and conditioning programs should be designed to restore and optimize the activation sequences and task specific functions of these muscles.

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Background and aim: Belts and back supports are frequently used to prevent low back pain. Despite many studies, there are not sufficient evidence and conclusive consensus about the effects of these supports. The purpose of the present study was to determine the effect of lumbosacral supports on motor control pattern during combined trunk motion.

Materials and Methods: 30 healthy young men were selected for the study. Temporal parameters of motor control and activity level of three pairs of trunk muscles were measured during combined trunk motion against minimum resistance and resistance equal to 50% of maximal isometric strength, under with and without back support conditions.

Results: By application of a lumbosacral support, movement response time was significantly decreased under minimum resistance (P=0/004). Application of support decreased reaction time and motor time under two resistance conditions significantly (P<0/05). No significant changes were found in trunk muscle activity levels following wearing a back support (P>0/05).

 Conclusion: By application of a lumbosacral support, individual reaction time was decreased. Although back support did not change the trunk muscle activity level, but the erector spinae muscle efficiency was increased to initiate desired movement.

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Background and aim: Neck muscles contract dynamically in the majority of daily activities. Athletes, agricultures and industrial labors are predisposed to muscular fatigue. Aim: The aim of the present study was to compare the effect of dynamic fatigue on power and frequency domains of EMG spectrum.
Material and methods: In this study 20 healthy young men contracted neck muscles dynamically, until muscular fatigue occurs. Surface electromyography was recorded of levator scapula, neck paraspinals and upper trapezius, as neck extensors. The effects of dynamic contraction on frequency (Median Frequency) and Power domains(RMS) were compared before and after fatigue.
Results: The results of the present study indicated that MedF decreases following dynamic fatigue (P<0.05). After dynamic fatigue, RMS of levator scapula and upper trapezius increased significantly (P<0.05). Regarding to significant decrease of RMS and increase of MedF, paraspinals encountered with force reduction .
Conclusion: Changes of MedF and RMS indicated that a continuous dynamic contraction tends to exhaust levator scapula and upper trapezius but decreases paraspinals force.

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Background and aim: The aim of this study was to verify the relationship between pelvic tilt and lumbar lordosis with muscle tightness, muscle strength, BMI, and age in standing position.

Material and methods: In this study, 75 healthy female subjects participated with age range 20-70 years, mean (SD) = 40.66 (13.69). Pelvic tilt and lumbar lordosis were measured in standing position with pelvic inclinometer and flexible ruler respectively. The length of muscles, including: erector spinae, iliopsoas, rectus femoris, hamstrings, tensor fascia lata & ilio tibial band, and gastrocnemius were assessed by Schober, Thomas, Ely, 90/90 SLR, Ober tests and passive dorsiflexion of foot, respectively. The strength of muscles, including: rectus abdominis, transversus abdominis, left & right obliqus, Gluteus maximums & medius, and quadriceps were evaluated by manual muscle tests.

 Results: The relationship between pelvic tilt and lumbar lordosis with muscle strength, BMI, and age was poor. Muscle tightness and muscle strength had no significant effect on pelvic tilt and lumbar lordosis.

Conclusion: The results of this study indicated that the evaluated variables including: pelvic tilt and lumbar lordosis, have poor correlation with muscle tightness, muscle strength, BMI, and age. 

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Background and aim: Rehabilitation treatments have significant role in reducing the disabilities of Cerebro Vascular Accident (CVA). Due to great role of upper limb in the function of individuals particularly in Activity of Daily Living and the effect of stability of shoulder girdle on hand function, the aim of this study was to study the effects of Progressive Resistive Exercise on shoulder extensor and abductor muscles isometric strengths in adult hemiplegic.                                                                                  

Material and methods: 17 adult hemiplegics patients (50-70yrs., mean =60.52, SD=7.22) with RT side dominancy and 6 months after stroke, participated in this study. All procedures were approved by ethical committee of TUMS and written consents were also taken. Patients were familiarized with the procedure and shoulder extensor and abductor muscles isometric strengths were measured by dynamometer.                                            

Results: According to results of our study, shoulder extensor and abductor muscles isometric strengths showed significant differences between mean scores of pre and post intervention (P<0.05). Progressive Resistive Exercise improved 34% in shoulder extensor muscles isometric strength and 27% shoulder abductor muscle isometric strength.                                 

Conclusion: Results of our research showed that progressive resistive exercise approach is a useful method for increasing the isometric strength of shoulder extensor and abductor muscles. Therefore, it might be concluded that improvement of strength of shoulder muscles could result in stability in shoulder girdle and consequently might affect on hand function in hemiplegic patients.                                                             

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Background and Aim: Muscular fatigue is common problem that an athlete faces repeatedly during sport competition or therapeutic exercise. Undoubtedly¸ fatigue affects the precision of subjects’ performance and limits the range of physical and sport activities. Muscle fatigue advantages and disadvantages have been reviewed in many previous studies. To challenge this controversy fatigue evaluation requires reliable, stable and precise methods of analysis itself. Researches on muscle strength and subject’s perception of fatigue have been done in many studies. Therefore researchers in this study focus on temporal stability of both subjective perception of fatigue and produced muscle torque after fatigue.
Materials and methods: Fifteen healthy female between 20-30 years of age, who at least had some nonprofessional light sporting activities once a week, volunteered in this research. Each of volunteers was evaluated in 3 different sessions. The first session was to familiarize the volunteers with the Isokinetic tests. For the main test, each of the volunteers was evaluated once and then after one week interval. At each session after warm up, perceived fatigue was measured using Visual Analog Scale. Then Average peak torque and average power maximal concentric Isokinetic of quadriceps were measured at the velocity of 60 degrees per second. To perform the fatigue protocol, subjects were asked to perform successive maximal quadriceps contractions until the three subsequent quadriceps torque output drop below 50 percent of maximal torque output. Afterwards, for re-measurement average peak torque, average power and perceived fatigue were evaluated similarly.
Results: The interaclass correlation coefficient (ICC) of average peak torque¸ average power and visual analog scale before performing fatigue protocol were calculated %81.6, %87.4 and %47.9 respectively. The repeated ICC after fatigue has estimated %59.9 ¸%64.4 and %96.6 respectively.
Conclusion: This research demonstrated that Isokinetic temporal stability parameters were high before fatigue. In other words, both torque and power are reliable in two repetition times in a session, as well after one week interval between. After fatigue the stability rate of torque and power recorded by Isokinetic were repeatable and this repeatability has been moderate to high. However VAS showed a completely opposite results, in which before fatigue the stability of imagined local fatigue perception has been very low and was not significant, although after fatigue the VAS showed high repeatability.

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Background and Aim: Biomechanical conditions of limbs can affect on motor unit recruitment (MUR) markedly. Surface Electromyography (SEMG) is an approach for evaluation of muscle activities and onset time during different functions. The purpose of this study is to use SEMG for detection of central motor control in different functions of knee extensor muscles.

Materials and Methods: Ten healthy subjects contributed in this study. They were done five repetitions of knee flexion/extension in open and close chain separately during recording of SEMG simultaneously. Integrated EMG (iEMG) of three middle repeated cycles were detected according to chain (open- close) and kind of contraction (concentric- eccentric).then the Average of three slope of iEMG compared to each other. 

Results: There were not significant differences in MUR of three extensor muscles for concentric and eccentric contractions in open chain but vastus medialis and lateralis muscles showed significant changes in close chain (P<0.05). Result showed that there were significant differences of MUR for two kind of muscle contractions between open and close chains (P<0.05).  

Conclusion: Recruitment of motor units has not shown difference in open chain between concentric and eccentric contractions. This process indicates representative similarity of control pattern in two kind of contraction in open chain. Concentric contraction at close chain cycle has more MUR in comparison with eccentric contraction. It is equal to more interference of contractible compartment in concentric to eccentric contraction. This happens due to the nature of two kind of contraction particularly in close chain cycle. Comparison between two chains indicated that more motor units contribute in close chain (concentric and eccentric). It means that motor unit recruitment increased due to effect of increase of load in close chain. 

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Background and aim: Assessment of hip strength needs a reliable method. Hand-held dynamometers are appropriate alternatives for manual muscle testing and isokinetics. Stabilizing the dynamometer with hand will increase error in measurements. The purpose of this study was to compare the test-retest reliability of hand-held dynamometer fixed by hand and fixed to a new stable frame for measuring hip extension, abduction and external rotation strength in healthy female athletes.
Materials and Methods: Normalized average and peak values of torque of three successive trials for each muscle group were calculated in two sessions one week apart in ten healthy female athletes. Strength was measured with hand-held dynamometer fixed by hand and fixed to the stable frame in each session. Intra-class correlation coefficients (ICC), coefficients of variation (CV) and standard error of measurement (SEM) were calculated to determine the reliability.
Results: For hip extension, abduction, and external rotation strength measured by hand fixation. The ICC ranged from -1.22 to 0.6, the CV ranged from 8% to 33% and the SEM ranged from 0.007 to 0.04. For strength measurements with stable frame, the ICC ranged from .93 to .96, and CV ranged from 5.26% to 7.94%. The range of the SEM was from .004 to .08.
Conclusion: Measurements of hip muscles strength with a dynamometer fixed to a stable frame showed higher reliability than fixation by hand in young female athletes. These findings support the error within hand fixation of dynamometers and the necessity for providing better fixation.

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Background and aim: Cognition of fatigue effects on motion response can improve treatment approaches. Determination of mechanism (maximal voluntary contraction and repetition of movement) that cause change of central responses and neuromuscular transmission have specific emphasis in evaluation and treatment of patients. Following fatigue it is arguable which is more important, neural or osteo-ligamental components. Behavior of para spinal muscles due to their roles in control of posture and spinal alignments are more importance. Gesture and motion pattern of neck and lumbar column following fatigue is due to accession of disorder in neuromuscular junction (NMJ) or limitation in reflex response at this system. Reflex influence is not just for muscle fatigue but also it appeared in synergic muscles. It is clear that stimuli and inhibitory ways have important role in this process.
Materials and Methods: Twenty normal subjects (10 female and 10 male) contributed in this study. Tests were including: 1- Training and warm up 2- Placement of recording electrodes on neck extensor muscles at second and forth spinal vertebra of dominant side. 3- Five motion of neck flexion and extension in sitting position at full range without external load. 4- Fatigue test, contain A- Maximal isometric contraction at middle range about 3 minute, which were controlled by a dynamometer until onset of fatigue. B- Fifty dynamic and cyclic motions of neck flexion and extension in full range of it. 5- Perform five motions similar stage 3 immediately after muscle fatigue. Three middle cycles were chosen for evaluation. Degree of off activities in flexion, degree of onset of activities in extension, silent period and mean of muscles activities (RMS), before and after fatigue selected for analysis.
Results: Comparison of two type of fatigue indicated that there are significant differences between them. Range of motion and eccentric activity were similar for two conditions. Isometric fatigue showed more effect than cyclic condition.
Conclusion: In neck motions flexion relaxation occurred. Dynamic motion and isometric activities caused muscle fatigue and changed silent period. This period reduced and it means that onset of extensor muscle activities occurred very soon and moved to middle and outer ranges. In this manner, naught privilege mechanical of non contractile elements in neck region is cause of this reduction. On the other hand extensor muscles have more responsibility for control and preservation of posture. Comparison of two approaches indicated that isometric activity produce more fatigue and spectral indexes such as median and mean frequency reduced markedly.

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Background and aim: Many studies have been carried out about bedrest and its effects on different systems including musculoskeletal,neuromuscular,cognition and vascular systems throughout the world.The purpose of this paper is to review systematically all Berlin Bedrest Studies on musculoskeletal system.The focus of this review is  mainly Second  Berlin Bedrest Study (2^nd BBRS) supported by European Space Agency(ESA).Such studies provide a chance to study the specific effects of immobilization without interference of other diseases.
Materials and Methods: A literature search was carried out using MEDLINE and ESA database to assess existing literature about the effect of bedrest on musculoskeletal system published by Berlin Bedrest Studies.It has been searched for efficacy of interventions  as high load resistive exercise and whole body vibration,as well.
Results: Fourty six articles have been found from 2000 to 2011year: 2 articles in 2000 and 2003,the other ones  between 2005 to 2011. Seventeen  articles were related to muscle and intervention on it,three ones about bone and related intervention on it,four  ones related to both bone and muscle and twenty two ones about the other systems  such as heart,vesseles,sleep and cognition.
Conclusion: According‏‏‏ to study results,bedrest has widespread effects on musculoskeletal system specially in early bedrest . These  effects remain up to 180 days  after bedrest course.Thus,high load resistive exercise and vibration should be prescribed in early stage of bedrest to reduce the detrimential effects of prolonged bedrest.