جستجوی مقالات مرتبط با کلیدواژه « فعالیت الکترومایوگرافی » در نشریات گروه « پزشکی »

The aim of the present study was to comparison of the effect of polyurethan thermoplastics military boots mileage on lower limb muscle activities during running in people with and without back pain.

The statistical population of the present study consisted of healthy men and with low back pain in Ardabil province. A statistical sample of 30 people aged 20-25 years was selected by available sampling and participated in the present study. Statistical samples were divided into two groups. There were 15 patients in the low back pain group, and the second group of 15 people as the healthy group. They received two new and used pair of boots. They were made of thermoplastic polyurethane. muscle activities of the right leg were recorded during running. Two-way ANOVA was used for statistical analysis at a significance level of 0.05.

Findings showed significant main effect of boot type for rectus femoris (p=0.037 d=0.146) during loading phase and gluteus Medius (p=0.006 d=0.242) during push-off phase. Findings showed significant main effect of boot-by-group interactions for rectus femoris during mid-stance (P=0.020; d=0.161).

The results of this study showed that the type of boots used can be effective in preventing lower limb injuries and absorbing shock and impact in people with low back pain, on the other hand, the use of new thermoplastic polyurethane operational boots is suggested for people with low back pain. Our findings showed that the observed changes in muscle activity variables are more obvious in second-hand boots. It seems that changing boots after 6 months of heavy wearing is suitable for people.

Activity of knee joint muscles can influence the magnitude of ground reaction forces during jump-landing tasks. The objective of the present study was to examine the relationship between electromyography activity of the knee joint muscles and ground reaction forces during single-leg drop landing task.      
A total of 20 healthy male athletes (mean ± standard deviation, age 25.4±4.45 years) participated in the present correlational study. Activity of knee joint muscles, including quadriceps, hamstrings, and gastrocnemius, at pre and post landing phases were analyzed and their relationships with ground reaction forces (vertical, anterior-posterior, and medial-lateral) were assessed during single leg vertical drop landing task. Pearson correlation coefficient was used for data analysis.   
The results demonstrated significant negative correlation between lateral gastrocnemius muscle activity and all components of ground reaction forces (P= 0.001). Also, there was a significant positive correlation between medial gastrocnemius activity and all components of ground reaction forces at pre landing phase and also a significant negative correlation with vertical and anterior-posterior component at post landing phase (P=0.001). Moreover, there was a significant negative correlation between lateral hamstring activity and anterior-posterior ground reaction force at post-contact phase (P=0.001).
It seems that gastrocnemius (medial and lateral) and lateral hamstring muscles play important roles in adjusting ground reaction force components during single leg vertical drop landing task. According to the results of the current study, it is suggested that rehabilitation specialists focus especially on activation exercises for gastrocnemius (medial and lateral) and lateral hamstring muscles in order to prevent anterior cruciate ligament injury.

Swayback posture is one of the spinal abnormalities and one of the important causes for the pathology of the Lumbo-Pelvic region. However, due to inadequate information about the method of evaluation among researchers, and also lack of agreement about the muscular changes, less attention has been paid to muscle activity in this posture. Therefore, the purpose of the current study was to compare the electromyographic activity of trunk and hip muscles during standing in females with and without swayback posture.
For this purpose, 30 inactive females selected using purposive sampling method were assigned into two groups of swayback posture and control. Pelvic tilt and sway angles were obtained with camera and electromyography signals from the thoracic and lumbar erector spine, lumbar multifidus, gluteus maximus, medial hamstring, rectus abdominis, external oblique abdominal, and rectus femoris muscles during standing posture.
The results of independent t-test demonstrated significant differences between swayback posture and control groups in the pelvic tilt (p 0/001) and sway angles (p 0/001). Also, no significant differences were shown between the two groups in the electromyographic activity of erector spine, lumbar multifidus, rectus abdominal, external oblique, and hip extensor muscles during standing (p > 0/05). Moreover, there was a significant difference between the two groups in the amounts of activity of the rectus femoris muscle (p ꞊0/012) and internal oblique (p ꞊0/018).  
The findings of the present study demonstrated that there are similar muscle contractions in the trunk and hip muscles between two groups of sway back posture and control, which contrary to the previous studies, the perception of passive swayback posture has been somewhat violated. Hence, this can provide a better understanding of the sway back posture for trainers and athletes in assessment and rehabilitation.

The aim of this study was to investigate the effect of the heel wedges on the electromyography activities of the selected left and right lower back muscles during load lifting.
A total of 17 male subjects voluntarily participated in this quasi-experimental study. The selected subjects lifted a box, weighing 10% of their body weight, above the height of their hip joint, descending as far as the thigh, parallel to the ground, and then ascending to the starting position. The above task was performed nine times in two conditions, including with and without the heel wedges. Using the ME6000 electromyography system, the activity level variables were normalized and the median frequencies of the erector spinae (ES) and the multifidus (MU) muscles were recorded. The subjects also held the box for 30 s in the standing position with stretched hands. The paired t-test was used for the data analysis.
The results showed that during static load lifting using the heel wedge, the median frequency of the right ES muscle changed significantly (P0.05).
During such occupational tasks, a decrease in the activities of the selected lower back muscles with the heel wedge might result in a delay in the onset of muscle fatigue. The above findings might be used in the design of shoes, suitable for the work environments. However, further investigations are needed in this area in order to provide more accurate results.

In recent years, it has been focused much attention on gait analysis. Factors such as speed, age and gender affect gait parameters. The purpose of the present study was to compare the electromyographic activity pattern of knee two-joint muscles between younger and older subjects in different gait speeds.
Matterials & The method of current study was analytical cross-sectional method in which 15 healthy young men and 15 old men, were selected conveniently. Electromyographic activity of rectus femoris, biceps femoris, semitendinus and gastrocenemius were recorded during walking with preferred (100%), slow (80%) and fast (120%) speeds in a 10 meter walkway. Normalized RMSs of muscles were compared using RM-ANOVA and Tokey’s tests by SPSS 18 software.
According to results, RMSs of rectus femoris in midstance (P According to the results, older subjects have more muscle co-contraction around knee at high speed in midstance phase than younger subjects. These age-related changes in muscle activity, leads to increase in joint stiffness and stability during single support, and probably play a role in reducing push off power at faster speeds.

Although the effects of whole body vibration (WBV) on the electromyographic (EMG) response of some muscles have been investigated in different studies، the effect of WBV on different types of motor units is not clear yet. The aim of the present study was to assess the different effects of a short-term WBV training on different motor units. Soleus (SOL) and gastrocnemius lateralis (GL) muscles were selected as the representatives of slow- and fast-twitch muscles، respectively. Twelve healthy young women (mean age 25. 66 ± 2. 71 years; mean height 161 ± 5. 6 cm; mean weight 66. 5 ± 5. 42 kg) were randomly allocated into the sham (n = 6) and WBV (n = 6) groups. The maximal isometric voluntary contraction (MIVC) of SOL and GL muscles was recorded before the initiation and after the termination of 12 training sessions. The training program was composed of the isometric squatting in both study groups such that in the sham group، the WBV machine set as off and in the WBV group، isometric squatting was offered in combination with whole body vibration (frequency of 30 Hz and peak to peak amplitude of 3 mm). The root mean square of EMG of soleous and gastrocnemius muscles was not statistically different between the two groups before training (P > 0. 05). The 12 sessions of training did not induce any statistically significant change in the muscle activity (EMGrms) of the SOL and GL muscles in either group (P > 0. 05). Although the RMS response of lateral gastrocnemius showed increasing behavior from the sham to the WBV groups، there was no significant difference in EMGrms values of these two groups (P > 0. 05). The difference value of EMGrms for soleus muscle did not also show any significant difference between these two groups (P > 0. 05). Despite the fact that EMGrms increases in soleus and gastrocnemius muscles were not statistically significant after WBV training، monitoring the response pattern in these two muscles between the sham and WBV groups is indicative of a positive effect of WBV on the lateral gastrocnemius motor units as a fast-twitch muscle.

The lower extremity deformities have been co nsidered to change the relations between body segments. Postural stability could be affected by these changes in the alignment and positioning of the body segments. The purpose of this study was to examine postural response and surface electromyographic activity of selected lower limb muscles to recover upright posture following a sudden external perturbation among individuals with genu valgum in comparison with age matched healthy controls. In this case-control study, sixteen subjects with genu valgum and sixteen age-matched healthy controls were participated. With unexpected perturbation, the displacement of the center of pressure (COP) and surface electromyographic activity of selected lower limb muscles were collected. Data were analyzed using independent t-test (P<0.05). The genu valgum group had a greater COP displacement after perturbation in comparison with the control group (P<0.05). Activities of some of the lower limbs muscles were significantly higher in genu valgum group in comparison with controls group after perturbation in different directions. These findings illustrate that abnormal lower limb alignment as risk factor can decrease postural reaction strategy in response to a sudden balance perturbation. Designing a strength training program for vastus medialis muscle may have beneficial effects in the prevention of knee injuries in individuals with knee valgus deformity.

Acute muscular exercise generally induces the development of fatigue that has detrimental effects on performance. The purpose of this study was to examine the effects of acute eccentric exercise (ECC) training on torque and electromyography (EMG) activity of human elbow flexors. Sixteen healthy male active subjects with no previous history of pathology of the elbow performed ten sets of 5 repetitions of maximal eccentric muscle actions training (ECC-T) with one arm using the calibrated electronically Biodex isokinetic dynamometer (System 3: Biodex) at 120° s-1 velocity of the dominant elbow flexors determined at the elbow joint of 90° (1.57 rad). Changes in maximal voluntary torque and EMG activity (root mean square (RMS)) of biceps brachii and brachialis muscles were measured after acute ECC. The acute ECC induced a significant torque reduction (P < 0.01). During the exercise session, mean maximal voluntary eccentric torque reduction reached 28.21 ± 10.20% (P < 0.001). Indeed, average maximal eccentric torque values dropped from 64.11 ± 11.28 N/m for the first three muscle actions of the first set to 46.05 ± 10.66 N/m for the final five muscle actions of the tenth set. Concurrent to the torque decrease, the RMS values of the biceps brachii and brachialis muscles at the same velocity were significantly lower after the exercise session (P < 0.05). After the acute exercise session, mean RMS values of the biceps brachii and brachialis muscles reduction reached respectively 15.16% and 13.87% (P < 0.001). These results showed that an acute ECC induced a significant voluntary maximal torque and EMG reduction of human elbow flexors during eccentric muscle actions.