جستجوی مقالات مرتبط با کلیدواژه « الکترومایوگرافی » در نشریات گروه « تربیت بدنی »

Lifting heavy objects without skill, carries a very high risk and causes injury to the back muscles. Electromyography can provide the best method of lifting heavy objects. In this study, four healthy females (1 female, 40 years old and 3 females, 20±3 years old) and six healthy men (2 men, 50±5 years old and 4 men, 20±5 years old) voluntarily participated, by obtaining four different electromyography signals. The obtained data were windowed every 15.5 seconds and the 4th order Butterworth filter was applied to the data. Then the variance, RMS and average of the data were calculated. The most muscle activation happened in performing ergonomic movement, which shows that in this case, the least pressure is applied to other muscles. Future studies can be defined on the impact of using the exoskeleton in identifying and assisting in load carrying movement.

Optimal performance of complex Forehand stroke needs coordination between postural adjustment and focal movement. the purpose of this study was to investigate the relationship between onset time and magnitude of Anticipatory Postural Adjustment (APA) and constant and variable error of Table Tennis Forehand stroke among skilled and novice players. For this, skilled (n=10) and novice (n=10) participants, perform Forehand stroke under Coincident Anticipation Timing (CAT) paradigm and EMG of selected postural muscles were simultaneously recorded. The results of investigating the EMG data showed that in all postural muscles, APA was occurred before focal movement initiation. In addition, the results of two way MANOVA test showed that in comparison with novices, skilled players had higher accuracy and lower variable error in their performance (P<0.05). Also, the result of Pearson moment correlation test revealed that among skilled players, both early onset time and greater magnitude of APA correlated with higher accuracy (P<0.05); however, only the APA’s onset time correlated significantly with both accuracy and variability of novices’ performance (P<0.05). Lower variable error in skilled players’ performance in comparison to novice counterparts and yet lack of correlation with onset time and magnitude of APA, probably indicates the consolidation of internal models as a result of practice and long term experience of skilled players in that sports skills.

Massive amount of practice over many years raise the question that handling class of action by generalized motor program may modify over years. The purpose of the present study is to provide evidences to investigate this hypothesis by examining the pattern of co-activation and agonist to antagonist activity ratio. Seven experienced darts players were asked to execute from standard dart distance (fourth distance) and six other farther and nearer distances, making 252 throws. Relatively, the results showed that at least in five from the seven samples, there was a significant difference in muscle co-activation between fourth and six other distances. These findings do not support the existence of a generalized motor program at fourth distance so that performance of elite players met limited generalizability

Kayak Riders involves repetitive stress movements, and most of the injuries are overuse. Therefore, the aim of this study was to determine the electromyographic activity and the amount of fatigue of selected shoulder muscles during 2 km rowing.

This is descriptive and quasi-experimental study and the sampling method is purposeful. The statistical sample was eight female national rower who were selected according to the criteria for entering and leaving the research. For test, the 2-kilometer Kayak ergometer was used. Initially, the MVIC test was used to normalize the results. Then, recording the level of muscle activity was done by Surface Electromyography (16 Channel, manufactured by Bayamed Iran). For data analysis, ANOVA with repeated measure design with a significant level of 0.05 and SPSS software version 22 was used.

The results showed that the distance of rowing 2 km had a significant effect on the electromyographic activity of Anterior Deltoid(P≤0.025), Biceps Brachii(P≤0.001), Triceps Brachii(P≤0.041) and Pectoralis major (P≤0.001). There was a significant effect on the fatigue rate of Anterior Deltoid(P≤0.001), Biceps Brachii(P≤0.001), Triceps Brachii(P≤0.049) and Pectoralis major (P≤0.001).

The results of this study show that 2 km rowing has a risk factor for injury in the shoulder girdle structure.The obtained results can be used to design a suitable program to prevent injury and improve of the kayak.

Surface stiffness is a factor affecting the injuries since any change in in the amount of this parameter leads to the increased applied forces. This is a quasi-experimental, causal-comparative, and applied study. The statistical population included 14 volleyball players aged between 18 and 20. The muscles’ electrical activity was recorded by an 8-channel electromyograph based on the SENIAM protocol (Surface ElectroMyoGraphy for the Non-Invasive Assessment of Muscles) on four selected muscles of the lower limb. Mean and standard deviation (SD) were employed for data description, Shapiro-Wilk test for the assessment of data distribution normality, analysis of variance with repeated measures for the effect of surface type on the research variables, and Bonferroni post hoc test was used for the assessment of differences. Furthermore, the repeated measurement test’s results revealed no significant difference between groups in terms of the peak muscle activities in Vastus lateralis muscle and Biceps femoris muscle when jumping and landing on tatami, grass, and sand (p≤0.05); however, the surfaces were significantly different in the tibialis anterior muscle and gastrocnemius muscle (p = 0.00). Besides, there was no significant difference between co-contractions in knee and ankle joint (p≤0.05); the difference was that in the knee joint, the highest average co-contraction was seen on the grass and its lowest rate on the sand, while in the ankle joint, the lowest rate was seen on the sand and the highest rate on tatami.

 back pain is one of the most common health problems in different societies, especially in industrialized countries. This study aimed to compare the electromyography activity of abdominal muscles and hamstrings in women with low back pain in different lifting positions. 

 The present study was a quasi-experimental and laboratory study. The statistical sample consisted of 10 women with back pain and 10 healthy women for whom using 16-channel EMG system and surface electrode, electromyography activity of the right muscles (Rectus Abdominis, Internal Abdominis, External Abdominis, and Biceps Femoris muscle and semitendinosus) while lifting with three Squat, Stoop and freestyle methods were recorded. Data analysis was performed using SPSS software. Analysis of variance was performed by repeated measures and independent t-test at a significant level (P≤0.05).

 In the stage of lifting weight, the Internal Abdominalis muscle, healthy individuals were more active in the squat technique than in Frees and Stoops, and the patients, Semitendinosus muscle was less involved in the freestyle technique than in the squat technique, but in lowering, weight Semitendinosus muscle of back-pain patients showed more activity in freestyle technique. 

 In the present study, the freestyle method in patients with back pain is safer for lifting the load than the other two methods. Also, for sports rehabilitation in people with back pain, special attention should be paid to the role and strengthening of the hamstring muscles so that the patient has better performance for lifting activities.

Whole body vibration (WBV) exercises appear to be an effective alternative to improving physical function in the elderly. The aim of this study was to compare the effect of eight weeks of whole body vibration exercises and rope skipping training with two different intensities on electromyography indices of elderly men.

36 elderly men (mean age 65.8 ± 4.2 years; height 169.3 ±3.9 cm; mass 77.1 ± 4.6 kg; body mass index 26.9±0.7 kg.m2) were selected by purposive and available sampling method and randomly divided into three groups of high intensity (N=12), low intensity (N =12), and control (N =10). Vibration exercises were performed with a frequency of 40 Hz and 25 Hz, with a range of 3 mm . In rope training, intensity was applied with 30-35 jumps per minute for both groups. Electromyographic indices of biceps brachii, triceps brachii, rectus femoris and biceps femoris muscles including activation of the ratio of agonist and antagonist muscles, muscle amplitude, and average muscle power frequency were calculated in the pre-test and at the end of eight weeks.

The electromyographic indices in the high intensity and low intensity training groups showed a significant improvement compared to the control group (p≤0.05). There was no significant difference between the two training groups in any of the variables (p>0.05).

The both the intensity of the combined vibration-rope programs have improved the function of electrical muscle activity in the upper and lower limbs of older men.

Most of sport injuries occur during fatigue. The aim of the present study was to evaluate the effect ofMost sports injuries occur during fatigue. The aim of the present study was to evaluate the effect of fatigue protocol on lower limb muscular activities in individuals with genu varus during running with agility shoes. In this study, 14 individuals with genu varus and 15 healthy control ones aged 20-30 years volunteered to participate. Muscle activities were recorded using a Biometric system. Findings demonstrated greater gluteus medius activity in the healthy group compared to the genu varus group. The main effect of fatigue on tibialis anterior activity during the loading phase and mid-stance phase was significant. Overall, because of different tibialis anterior and semitendinosus performance in the genu varus group compared with the healthy group during running before and after fatigue protocol, rehabilitation of these muscles is essential in genu varus individuals.

The purpose of this study was to compare the effect of plyometric training pre and post maturation period with soccer training on electromyographical index and soccer players performance. 30 students of soccer playerchr('39')s pre maturation period (weight 32.38±6.59 kg, age 10.35±0.59 years, and height 141±0.06cm) and post maturation period (weight 43.79±10.96 kg, age 15.43±0.72 years, and height 156.84±0.09 cm) were selected. Subjects in the experimental group were 15 students before and after maturity period. To evaluate the age of the indices such as height, age, dental and bone age (radiographic method) was used. Then, for homogeneous groups of index of biological age radiography was used by radiologists. Before and after 4 weeks of training,, functional tests of two 20 meter speed, agility, vertical jump and also Amplitude  for vastus lateralis muscle Were taken. The result by using  Paired t-test showed that in pre maturation group in the vertical jump, agility and 20 meters there was a significant difference (P=0.002,P=0.006,P=0.001) and the other variables there was no significant difference. In variations between the groups, independent t-test showed that only significant differences was found in the test 20 meter speed (P = 0.007) and in the other variables not significantly different. The results showed that plyometric training in the Pre maturation group compared to post maturation group were more effect and these results can help in the design training for premature age groups

It is necessary to examine the changes of muscle co-contraction in different percent of fatigue-induced force reduction. The present study aims to investigate the effect of fatigue-induced force reduction of knee extension on muscle co-contraction. Ten healthy and active women aged 26.10±2.99 years performed fatigue protocol including 5 seconds of maximal voluntary isometric contraction (MVIC) of the knee extension and a 5-second rest. Muscle co-contraction was calculated for each subject in the repetitions in which the MVIC force was reduced by 10, 20, 30, 40 and 50% as compared to the pre-fatigue MVIC force. Knee extension force and muscle activity measured by Isokinetic and electromyography apparatus, respectively. The difference between co-contraction of vastus lateralis and medialis in different percentages of force reduction was not statistically significant. The co-contraction of rectus femoris and biceps femoris increased by 40 and 50% of force reduction compared to pre-fatigue co-contraction (P<0.01). Co-contraction of biceps femoris and vastus lateralis increased by 20, 30, and 40%, as well as co-contraction of biceps femoris  and vastus medialis increased 40% of the force reduction, compared to pre-fatigue co-contraction (P <0.05). The results, overall, showed that the change of co-contraction during fatigue is influenced by the selected muscle and the rate of force reduction. This finding can help researchers decide how neuromuscular fatigue effects on muscle co-contraction

The frequency spectrum of electromyography is one of the important indicators to identify the amount of fatigue in the muscles. The aim of this study was to evaluate the effect of quadriceps fatigue on the electromyography frequency spectrum in lower limb muscles in elite men during the Apdoliochagi. 14 male taekwondo players (mean age of 24.50±1.74 years) with at least 3 years of participation in national competitions were voluntarily and purposively selected with coordination of the taekwondo board of Ardabil province. A wireless electromyography system with 8 pairs of bipolar surface electrodes was used to record the electromyography activity of lower limb muscles during the Apdoliochagi (sample rate: 1000 Hz). Paired t test was used to analyze within-group differences (P≤0.05). Results showed a significant decrease in the frequency spectrum of electromyography in vastus medialis (P=0.042, d=0.93),vastus lateralis (P=0.044, d=0.90), rectus femoris (P=0.003, d=1.18), biceps femoris (P=0.020, d=1.13), semi tendentious (P=0.029, d=0.94) and gluteus medius (P=0.023, d=1.06) after fatigue compared with the period before fatigue. The results showed a significant decrease in the frequency spectrum of electromyography in muscles of the hip and gluteus medius after quadriceps fatigue. Although such results were not obtained in the muscles of tibia anterior and gastrocnemius, this difference can be attributed to the differences in muscle mobility in terms of motor behavior. So, coaches and players are recommended to focus on those exercises which increase endurance of quadriceps, hamstring and gluteus medius.

The purpose of this cross-sectional present study was to investigate the force-related fatigability in gymnast and untrained girls according to tanner stage. 60 gymnasts and untrained girls were divided into the three subgroups of children, adolescents and adults according to Tanner's scale. Subjects were referred to the laboratory in three separate sessions for familiarity and initial measurements, maximal test, and fatigue test, respectively. For the maximal test, each subject performed three maximum isometric contractions of the knee extensor at five different angles to determine the optimal angle of force production. The fatigue test included repeating five-second maximum contractions with five seconds of rest to reach 60% of maximum torque. The electrical activity of the rectus femoris muscle was recorded using an electromyography to measure mean power frequency (MPF). Two-way ANOVA was used for data analysis. There was a significant difference between the number of repetitions to fatigue in children compare to adolescent and adult (P<0.05), this difference (between children with adolescents and adults) was not significant in gymnast groups (p>0.05). However, the normalization of the torque drop based on the initial productive force (peak torque) showed a similar pattern in children and adults. This may indicate the importance of the peak torque in explaining fatigability between children and adults. It seems gymnastic training in pre-puberty period may shift the fatigability pattern toward adulthood pattern.

 This study aimed to examine the effect of fatigue on postural balance of young women using Electromyography (EMG) of lower extremity muscles and measuring the foot plantar Center of Pressure (COP) displacement.

Participants were 10 young women (mean age, 26.4±3.01 years; mean weight, 65.5±5.75 kg; mean height, 165±2.61; BMI, 24.08±2.08 kg/m2) with no history of lower limb injury or balance problems. To evaluate their static balance, the stork test was used and the foot plantar COP was measured by force plates. To measure fatigue, three parameters of muscle power (P), median frequency of muscle (F) and Root Mean Square (RMS) of raw EMG signals were calculated. Data were analyze din SPSS V. 16 and MATLAB software using Mann-Whitney U test.

fatigue had a significant effect on P and RMS parameters (P<0.05), but did not significantly affect the F. It increased P and decreased RMS. The highest change in the P parameter was seen in biceps femoris muscle; the highest change in the F parameter was related to semitendinosus muscle; and the highest change in the RMS parameter was related to gastrocnemius lateralis and gastrocnemius medialis muscles.

 There is a negative relationship between fatigue of the lower extremity muscles and balance impairment; by increasing the level of fatigue in the muscles, balance is more impaired.