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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: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: 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: Muscles that contribute in production of sound have an important role in specific language. Knowledge of normal activities of these muscles is very important in language dysfunction and pathologic conditions. Needle electromyography is complementary approach in clinical evaluations of above conditions but it is a painful method for evaluating of the patient. Surface electromyography can be used to neurophysiological behaviors and effect of treatment interventions and is accepted by scientific academies. The purpose of this study is appointment of new approach in this area.

 Materials and methods: Sixty eight healthy subjects (34 female and 34 male) in range of 20-30 years old were contributed after supplement of questioner form in this study. Subjects sat in a chair with arm rest and recording electrodes placed on muscles of Thyroarytenoid and Cricothyroid of both side (right and left) at middle and lower parts of throat, near of 1 cm from midline.  Silent activity and fricative voice (z-zh) and voiceless (s-sh) activities recorded randomly at 10 second with interval rest between them for 5 repetition. All of signals processed and then compared in time, frequency and non linear measurements.

 Results: Non linear values such as Percent of recurrence, Entropy were reduced significantly in fricative voice (P<0.05).

 Conclusion:  Surface activity recording of Thyroarytenoid and Cricothyroid muscles is possible and sensitive parameter is non linear values. Surface electromyography is new approach for assessment of above muscle in clinical evaluation of speech pathologic conditions.    

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Background and aim: Asymmetric motions of trunk, external forces and other occupational factors such as frequent bending and twisting, lifting and forceful movement contribute to low back disorders. However, the dynamic and three-Dimensional motions of trunk at varying exertion levels were not addressed in literature. Hence, the aim of this study was to investigate the movement pattern and motor output during resisted trunk three-dimensional motion. 

Materials and Methods: Thirty healthy male subjects randomly performed dynamic asymmetric trunk motion at four resistance levels (nominal resistance, 25%, 50%, and 75% maximal voluntary contraction (MVC) torque) while positioned in standing with the L5-S1 interspinous space aligned with the flexion / extension axis of isostation B200. Under each resistance condition, movement patterns (range of motion), motor output (maximum torque) of the trunk were measured.

Results: In general, with increasing resistance from nominal to 75% MVC torque, the maximum torque of trunk in different directions of motion (flexion, extension, right & left lateral flexion, right & left rotation) increased significantly (p= 0.000). With increasing resistance from nominal to 50%  MVC torque, the range of motion of the trunk decreased significant (p<0.0083), but no significant change was found in this variable between resistance conditions of 50% and 75% MVC torque (p>0.0083).

Conclusion: When the resistance level is increased , the created external forces  must be balanced by internal forces generated by trunk muscles. Because the muscles have short lever arms compared with the external forces, they must generate large amounts of forces, placing compressive and shear loads on the structures of the spine. Under these conditions, spine injuries may be enhanced.

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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: Swallowing disorder is one of the most important complaints of patients with upper motor neuron lesions.The rate of disphagia increases due to elderly subjects and brain injuries in our society Majority of these patients have hidden aspiration. Electromyographic assessment of swallowing can produce indicators of recovery and treatment effectiveness. This study tries to indicate pattern and recruitment of muscle activity in swallowing by surface electromyography.
Methods and Materials: Twenty healthy subjects (20-50) and ten subjects with swallowing dysfunction contribute at this study. Activities of bilateral orbicularis oris, buccinator, sternocleidomastoid and anterior region of throat muscles recorded during three stage of liquid swallowing include water, juice and honey by surface electrodes. Value of activity (RMS), duration of activity (Dur) , median (Mdf) and band (Banf) frequency of above muscles were measured.
Results: Healthy subjects indicated increase of RMS, Dur, Mdf and Banf of muscles, following increase of sweeten and viscose of liquid (P<0.05). Patients had more increase of this findings at oral muscles markedly, whereas Dur of throat muscle showed more increase in time (P<0.05). Comparison of between two groups indicated patients have more Dur time especially at throat muscles (P<0.05) and in contras reduce of activities and frequency parameters than healthy subjects (P<0.05).
Conclusion: Patients lean to keep liquid in oral phase and during throat swallow have more limitation. Patients may catch early fatigue and dysfunction for maintenance and keep of liquid particularly in throat region and it redound to change of trajectory of liquid to the respiratory tube. Therefore, rehabilitation protocols must enforce on coordination of oropharengeal muscles and recovery by movement therapy patterns.

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Background and Aim: In spite of massive knowledge increase and ergonomic correction, lumbar disorders extremely prevail in working environments. Efforts have been made in order to decrease prevalence of musculoskeletal disorders caused by lifting, carrying and pulling down objects by using some belts. The purpose of this research is to determine the effect of lumbo-pelvic belt in symmetrical load lifting on one of motor control indexes.
Materials and Methods: In this research twenty men were asked to lift objects with different weights of 5.5, 7.5, 9.5 and 12.5 kg in position of complete trunk and hips flexion and knees extension using and not using belt and put them on the target desk. Surface Electromyography has been recorded from two pairs of back muscles and three of abdominal muscles. 
Results: Lifting different loads with belt showed significant increase in symmetrical index (p<0.05). 
Conclusion:  Using belt brings about more coordination in trunk agonist and antagonist muscles activity while lifting the loads.  

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Background and Aim: Muscle fatigue is a factor that caused muscle injuries. Ability to perform movement without error and controllability has important role in reduction of injuries. Reproduce ability of motion is reduced after muscle fatigue. Evaluation of motor control can produce suitable conditions for assessment of these changes and help us treatment guide lines for prevention of injuries. The aim of this study was to evaluate motor control changes following onset of fatigue in patients with anterior knee pain as a physiological aspect.
Materials and Methods: Fifteen voluntary female (10 healthy, 5 patients with bilateral syndromes) participated in this study. During dynamic fatigue test (open and closed chain movements), muscle activities were recorded from bilateral vastus medialis, vastus lateralis and rectus femoris (20 healthy and 10 patients quadriceps muscles) by surface electromyography (sEMG). Five dynamic cycles of motions were selected before and immediately after fatigue and then average of three middle cycles were compared for Symmetry Index (SI) as motor control assessment.  Also Median Frequency (MDF) were computed as an indicator for onset of fatigue. 
Results: MDF reduced significantly in both groups. This reduction was markedly showed in patients group. Reduction of SI was significant after fatigue test. Comparison of SI between groups indicated that before fatigue there was significant difference but after fatigue test was not significant.  
Conclusion: Dynamic motions can produce muscle fatigue and reduction of MDF. High central control system used different synergies following pain and functional impairment. Synergy patterns change after dynamic motions fatigue and cause reduction of SI. This change is dependent to pain and functional impairment and has not a stable pattern. 

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Background and Aim: Whole Body Vibration (WBV), as a new exercise modality, can improve neuromuscular performance but, there is no study to assess the effects of WBV on the reaction time as an indicator of muscular performance especially in upper extremity muscles. Therefore, the aim of the present study is to investigate the immediate effects of WBV on timing parameters of upper extremity muscles. 

Materials and Methods: Forty healthy young women were randomly assigned in two groups of intervention (with WBV) and control (without WBV). In the intervention group, timing parameters (Reaction time (RT), Premotor time (PMT), Motor time (MT)) were measured by using EMG before and after the vibration (5 sets of 30seconds at 5 mm amplitude and 30 Hz frequency) session. The same protocol but without vibration was used for control group.

Results: Whole body vibration did not alter the RT significantly (P=0.253). Premotor time was increased significantly only in the triceps muscle (P=0.006). There was also a significant difference (P=0.003) in MT of the serattus anterior muscle between two groups.

Conclusion: It seems that WBV can induce different effects on upper extremity muscles. Whole body vibration has not any significant effects on the total RT 

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Abstract

Background and Aim: Nowadays personal lifting assistive devices, in order to reduce the load applied from the lifted weight to muscles - in particular lower back muscles, become more widely used. The objective of our study is to analyze an empirical model of a Weight Lifting Aid Vest (WLAV) during anterior flexion (anteflexion) and studying its effects on reduction of loads on the muscles in particular back muscles. To analyze this, the intensity of signals captured from involved muscles, during the lifting in two case of with and without WLAV, was studied by the use of electromyography amplifier.

Materials and Methods: In this process, 20 subjects who lifted 10-kilogram loads in semi-squatting position were participated. With the use of a tensile-compressive spring, embedded at the back of WLAV, the amount of body stretch and deflection of their hip and knees were measured. The influence of the WLAV on satisfaction during the lifting was studied.

Results: Data were collected from electromyography findings from eight involved muscles in back, stomach and feet. The results depicted that there are a overall reduction of 25.12-percent in activation of all the muscles and particularly a reduction of 57%, 28% and 26.5% in activation of external oblique, lateral hamstring, and erector spine, respectively. In contrast, there is 11% increase in activation of Gluteus Maximus in the case of usage of WLAV.

Conclusion: WLAV can significantly mitigate the activation of back muscles and rate of load insertion on muscles) P<0.005). It also clarified the tendency of the subjects towards users WLAV) P<0.005).

Keywords: Electromyography, Load measurement, Root mean square, Weight lifting aid vest (WLAV), Muscular demand

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Background and Aim: The aim of present study was to examine effect of attentional focus on balance performance and EMG activity of athletes.

  

Materials and Methods: The semi-dynamic balance task of 10 gymnasts (22.2±2.09 years old) with 3-5 years of experience in two periods, one in internal focus (focus on leg) and one in external focus (focus on stabilometer plate) was assessed. Postural sways were measuredby Biodexstabilometer and muscular activity of tibialis anterior and soleus muscles were recorded using ME6000electromygram device. Data were analyzed using paired t- test.

  

Results : muscular activity for controlling posture was reduced in external focus condition than internal focus. Postural sways is more in internal focus condition than internal focus.

  

Conclusion: Research findings (enhanced performance and reduced EMG) showed that antinational focus conditions (internal or external) have significant effect on athletes balance performance. In conditions that attention is focused on external feedback and information (rather than focus on body itself) balance is enhanced and requirement to muscular activity will reduce.

  

Key words: Attentional focus, Electromyography, Semi-dynamic balance

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Background and Aim: Many studies investigated the effect of ankle-foot orthosis on reducing the incidence of sprain. In this study the influence of elastic and semirigid stirrup type orthosis on the onset latency of peroneus longus muscle activity as the most important support of ankle- foot region in response to sudden perturbation was assessed in healthy group and athletes with functional ankle instability.

 

Materials and Methods: Thirteen healthy female athletes and 10 female athletes with functional ankle instability (17 to 27 years old) were perturbed unexpectedly by a custom made ankle perturbation system in frontal plane under three conditions of without orthotics, using elastic orthosis, and using semirigid stirrup-type orthosis. Simultaneous recording of electrical activity of peronus longus muscle was performed with surface electromyography.

 

Results: The results showed the significant differences between muscular latency of injured and control groups without orthosis (P=0.018). The onset latency reduced using each type of the orthoses in injured group but it was not significant (P>0.05).

 

Conclusion: Although the latency time of peroneus longus muscle response delay didn’t show significant reduction using orthoses in injured group, it seems that using orthoses leads to proprioception improvement and sensiomotor control increasement by stimulation of cutaneous mechanoreceptors.

 

Key words: Functional ankle instability, Invertory perturbation, Electromyography, Orthosis

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Background and Aim : The aim of this study was to determine the effects of fatigue due to plyometric training on vertical jump ability and activity pattern of rectus femoris of dominant leg of high jump of active girls .

 

Materials and Methods : Seventeen females , mean age (21.5 ± 0.76 years ) were randomly assigned to two experimental (n = 10 ) and control ( n = 7) groups. Experimental group performed plyometric training and control group had no activity. Before and after training , vertical jump test using Ergo jump and electrical activity of rectus femoris muscle of dominant leg using electromyography were tested . The results of vertical jump test showed a decrease in performance (p: 0.04, F: 4.5) and fatigue process was confirmed . The raw EMG signal based on deep jump phases was divided in three phases and only 2 phases of the first were analyzed . In every phase, the maximum activity , amplitude and total time were obtained .respectively. M ultivariate analysis of variance (2×2) was used to compare of post-test of two groups.

 

Results : After one session training , rectus femoris maximum activity of the experimental group showed a significant decrease in pre-activation phase of motor program .

 

Conclusion : This study showed that neural fatigue due to plyometric training can occur in motor program (especially in pre-activation phase of motor program ).

  

Keywords : Deep jump, Plyometric training, Vertical jump, Electromyography, Rectus femoris muscle.

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Background and Aim: The curves of the spine, especially lumbar lordosis, play an important role in the maintenance of an efficient upright posture and allow efficient absorption of the loads applied to the spinal column and increase the efficiency of the spinal musculature. Excessive lumbar postures, also called “hyperlordosis” and “hypolordosis” , are thought by some researchers to be indicative of altered muscle activity and stress patterns. Therefore tolerance of particular activities of daily living (ADL) of an individual with these postures is reduced. Despite the importance of neuromuscular control at spinal column maintenance and coordination, there are little investigations about the effect of thoracic and lumbar curvatures on trunk muscles activity. Therefore, the aim of this study was to investigate electromyographic behavior of trunk muscles in lordotic posture.

  

Materials and Methods: Twelve subjects with lordotic posture ( mean age 23.67 years, mean weight 56.67 kg, and mean height 162 cm) and eleven subjects with normal posture ( mean age 22 years, mean weight 59.36 kg, and mean height 164.91 cm) participated in this study. Subjects were asked to hold a load equivalent of 7% of her body weight.

  

Results: Data analysis indicated that there is not significant statistically difference in median frequency variable between two groups (p>0.05). But there is significant statistically differences at The percentage change in RMS of erector spinae and internal oblique muscles at three time periods between two groups. The percentage change in RMS of external oblique muscle has significant statistically difference at first and third time periods between two groups.

  

Conclusion: These finding reveal that excessive lumbar lordosis alter the activity levels of trunk muscles. Therefore, it seems that the use of posture correction exercises in therapeutic protocols is necessary for improvement of these changes. Also, it is recommended to do this research in dynamic tasks for attain of comprehensive information about the effect of postural deviation on electromyographic behavior of trunk muscles.

  

Keywords: Electromyography, Hyperlordosis, Posture, Prolonged load holding

  

  ^* Corresponding Author: Dr.AzadehShadmehr, Rehabilitation Faculty, Tehran University of Medical Sciences

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Background and Aim: Reliability or unreliability of the results achieved from recording of surface electromyography of muscles has always been questioned. The aim of present study was to  measure the reliability of the delayed reaction time of muscle electromyography of the knee joints on the exposure of unexpected rotary turbulence in the transverse plane from the area of supporting surface.

Materials and Methods: Twenty healthy women from 19 to 30 years old and free from any clear deformities in the lower extremities were participated in the present study. Surface electromyography of the six knee musculature was carried out for every subject separately in 4 situations including: External Rotation (Ext Rot) from plantar area on the transverse plane with bent and straight knee, Internal Rotation (Int. Rot) with the same conditions, Single Leg Stance situation in 4 stages, and repeatability of Intra Session through intra-class correlation coefficients when the muscles are in action on the exposure of turbulence in four applied forms were analyzed.

Result: The results from 24 analyzed forms showed that 18 forms of muscles at the time of action had moderate to high repeatability (Monroe Classification)

Conclusion: Regarding reliability, the muscles indicated different amounts in onset latency time, on the exposure of rotary turbulence, according to joint angle and the direction of applying rotation on the transverse plane. In respect to direction of rotation, most of the muscles indicated more reliability on the exposure of external rotation turbulence (clockwise) in relation to internal rotation (anti-clockwise) and also regarding the joint angle in turbulences with straight knee in relation to turbulences with bent knee. 

Keyword: Knee muscles, Surface electromyography, Reliability, Rotational turbulence

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Background and Aim: ACL injury is one of the most common sport injuries which undergo reconstructive surgery. Electromyography or recording of muscles’ electrical activity is a suitable means to assess changes in motor control system output. The goal of this study is to compare the lower limb muscles EMG activity during drop landing in individuals after ACL reconstruction and healthy subjects.

Materials and Methods: Eleven men who had undergone ACL reconstruction 6 to 24 months ago (Age 29±6 years old) and 11 healthy men (Age 28±2 years old) participated in the study. Amount of electrical activity for tibialis anterior, vastus medialis, vastus lateralis, semitendinosus and biceps femoris muscles was recorded using surface electrodes during drop landing and calculated for two time intervals. The amount of activity was measured in -150 to +50 and +50 to +180 intervals in relation to the landing moment. Subjective IKDC questionnaire and cross-over hop functional test were used to determine the subjective and objective functional level.  Independent t test was used to determine between-group statistical differences.

Results: Feed forward activity of semitendinosus (P=.041) and biceps femoris (P=.008) muscles were significantly higher in ACLR group and feedback activity of vastus medialis (P=.03) muscles was significantly lower in ACLR group. Healthy individuals showed higher score on both the functional test and IKDC questionnaire. (P<.0005)

Conclusion: Individuals who had undergone reconstructive surgery of ACL showed different muscular activity compared to healthy subjects and closer to ACL deficient individuals 6 months after surgery and routine rehabilitation.

Keywords: Anterior cruciate ligament reconstruction, Electromyography, Neuromuscular control

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Background and Aim: The structure and function of the hamstring and quadriceps can contribute to the development and process of patellofemoral pain syndrome. As open and closed kinetic chain exercises have different effects on the knee joint, the aim of the current study was to investigate motor control of knee joint in both kinetic chains according to voluntary response index aspect.

 

Materials and Methods: 12 healthy knees and 12 injured knees (6 females in each group) were examined. Surface electromyography were performed in knee muscles including vastus medialis oblique, rectus femoris, vastus lateralis and biceps femoris while the subjects were doing flexion-extension of knee joint by isokinetic dynamometer system and one leg semi-squat movement. Then voluntary response index was calculated.

 

Results: There were no significant difference between the patients and healthy groups (p>0.05). In the patient group, correlation between similarity index and magnitude was seen.

 

Conclusion: Probably in the low intensity patellofemoral syndromes, voluntary response index could not differentiate between healthy and the patient groups. In the patients with patellofemoral syndrome group, correlation between similarity index and magnitude may represent co-contraction in their muscles.

 

Keywords: Patellofemoral pain syndrome, Motor control, Voluntary response index, Surface electromyography