نشریه پژوهش در طب ورزشی و فناوری
پیاپی 21 (بهار و تابستان 1400)

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

As Squat is a popular exercise for support of lower extremity muscles in order to injury prevention this study has been hold to comprise the electromyography of vastus medialis and vastus lateralis muscles in three Squat techniques of man soccer players. 15 soccer players, aged 18-25 years old, who had regular exercise more than two years did open, closed and lung Squats exercise while electromyography of vastus medialis and vastus lateralis muscles were recorded. Data analyzed by using dependent and independent T test and repeated measure ANOVA. There was not significant difference of vastus medialis and vastus lateralis muscles’ electromyography during getting up, going down phases and also for different squat techniques. The vastus lateralis muscle show more activity in all conditions. Though, it is recommended that vastus medialis has bold role for controlling of squat exercise, reduction of Q angle and participants’ knee varus in this study can be the reason of antithesis.

Hamstrings (Hams) to Quadriceps (Quadr) strength ratio is known as a risk factor for Anterior Cruciate Ligament (ACL) injury and affects by knee and hip flexion angles. Gluteus Maximus (Gmax) muscle acts as a synergist for Hams in hip extension in a closed kinetic chain. The aim of this study was to investigate the effect of Gmax strengthening exercises on the kinetic and kinematic risk factors of ACL injury when single-leg landing from a jump. 25 volunteer women aged 18-30 years were assigned into control (n =13) and experimental (n =12) groups. Maximum isometric strength of Gmax, hip and knee joint angles and ground reaction force (GRF) was measured at landing, by dynamometer, 2D imaging and foot scan respectively,. After 8 weeks of 3 sessions of Gmax resistance training, Following the significant within-subject difference for GRF (F=5.245, P=0.032) by using Two-way mixed model ANOVA, Pre and post-test Differences were significant with 16.63% decrease (P= 0.038, t=2.354). Differences between pre and post-test peak force, time to peak, mean joint angles, impact and load rate were not significant (α = 0.05). According to a 4.55% and 3.47% increase in Gmax strength and time to peak force, and considering the fact that at the beginning of landing, the mechanical advantage of Hams is lower than that of Gmax, the risk of ACL injury could be reduced by reducing GRF following an increase in the Gmax strength.

Despite the importance of talent for sports, but it has yet received little attention. The purpose of this study was to present a pattern design for talent identification in  karate based on artificial intelligence algorithms. Subjects divided to adolescent elite karate athletes (n = 19) and non-karate athletes adolescent (n=20) by convenience sampling. Besed on previous literature, we selected and measured biomechanical and anthropometric variables. The normal distribution of all data was analyzed using Shapiro-Wilk test. Principal component Analysis (PCA) was performed to reduce the number of variables and identify the most important anthropometric and biomechanical variables. Then, for modeling, the neural network algorithm was used with three input layer (10 neurons), middle (7 neurons) and output (2 neurons). The results showed the most important anthropometric variables of adolescent elite karate athletes were thoracic subcutaneous fat, height, jump, static balance, grip strength, chest circumference, ankle circumference, abdominal subcutaneous fat and apparent length leg respectively. Also, percentage of correct classification and sensitive of data was high and 87% and 85% respectively. According to the results of this study, this method can be used for talent karate athletes along with other methods.

In recent years, efforts have been made to use non-invasive methods to achieve these angles. The aim of this study was to investigate the capabilities and reliability of a non-invasive system based on surface data mining using infrared depth cameras. To do this, you must first use a number of mathematical relations to create a cloud of points of the surface and to extract the desired deviations by geometric analysis of the map and surface topography. In this study, after extraction of cloud of points, the gossip method based on the second surface derivative was used to identify anatomical landmarks. Based on this, the body surface area was divided into a number of convexity, convection and parabolic. Then, by mathematical analysis of the surface topography map, the angles of a number of backward anomalies were estimated. To test the repeatability of this method, intra class correlation coefficient and minimum detectable changes were used to evaluate the relative and absolute  reliability. The results of this study showed that it is possible to identify landmarks using the second derivative method with appropriate accuracy. The results of the reliability survey also showed acceptable and high values ​​for the studied angles. Thus, it can be said that the use of this method has a good introverted reliability and can be a good alternative to radiography in continuous evaluations.

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

Knowledge of the relationship between performance and range of motion, helping to design training programs, comply of individual with the needs of children is, therefore, The aim of research the relationship between some of the lower extremity range of motion and biomechanical parameters of the boys was performed. Hundred students in this study were randomly selected. After measuring the range of motion of lower extremity, test speed, power, balance and agility of the subjects were recorded. By descriptive statistics to determine the mean and standard deviation of the method of multiple correlations to assess the relationship between the selected range of motion and biomechanical parameters of subjects were used. Hip flexion by speed, hip abduction and knee flexion by balance and hip flexion, hyper adduction and ankle dorsi flexion significant positive correlation by the agility, the rate of hip and knee flexion by power a significant negative correlation and with other lower extremity range motion parameters showed a significant positive association. According to the research findings, seem to be characteristics of the children lower extremity range of motion and identify performance indicators for various athletic field, can be used.

Determining the intensity of exercise in childrenchr('39')s sports programs has always been very important. The aim of this study was to investigate the rope skipping exercise with three different intensities on the acute response of salivary chromogranin A and alpha-amylase in girl students. 45 fourth grade students were divided into three groups (low, moderate and high intensity). They performed one session of rope skipping with three intensities of 50, 65, and 75% reserve heart rate, according to the metronome rhythm. The reserve heart rate was calculated by the Karvonen method. Samples of salivary immunoglobulin A and cortisol were collected before and immediately after the exercise and measured by the ELISA method. T-test and analysis of variance were used to evaluate the data. Alpha-amylase and chromogranin A increased significantly after all three intensities. It was Also shown that there is no significant difference between intensities in the amount of chromogranin A, While the amount of alpha-amylase in the group with an intensity of 75% of the reserve heart rate was more than 50%. Although more research is needed in this area, according to the present results, it can be said that probably a session of rope skipping with 50% of reserve heart rate has a less increasing effect on salivary alpha-amylase of girl students.

The purpose of this study was to investigate the effect of different hip joint postures on electromyographic activity of selected lower limb muscles during squatchr('39')s movement. Electromyographic activity of selected lower limb muscles of 15 healthy male students was recorded while performing a squat with neutral, 15°, 30°, 45° external and internal rotation of the hip. Friedmanchr('39')s nonparametric test was used to compare muscle activation at different angles of the hip rotation and the Wilcoxon test was used to determine within-group differences. The results of this study showed no significant difference in the activity of Vastus medialis (p = 0.052), Vastus lateralis (p = 0.102) and tensor fasciae lata (p = 0.193) in squat between different hip joint angles, but Significant differences were observed in gluteus medius muscle activation (p = 0.001) and biceps femoris (p = 0.015) in squat between different hip joint angles. Also, the results of this study showed that gluteus medius to tensor fascia lata activation ratio was significant in squat between different hip joint angles. squat with the external hip angles can be considered as an effective method to increase gluteus medius activation and gluteus medius to the tensor fasciae latae activation ratio. On the other hand, 45 ° external and 30 ° internal hip angles can be considered as an effective method to increase the biceps femoris activation.

although it is documented that the spine and hip alignments alter in scoliosis subjects, but the effect of these changes on the lower extremities’ biomechanics have not been well understood yet. So, the aim of this study was to compare hip, knee and ankle joint’s power generation and absorption during gait in patients with adolescent idiopathic scoliosis (AIS) and healthy controls.  

Using motion analysis system with 4 Vicon-460 cameras and two Kistler force plates, the kinematics and kinetics of gait was assessed in twenty girls with AIS and 20 matched healthy controls, then the power of the right and left hip, knee and ankle joints in sagittal plane was calculated. Data was analyzed using ANOVA statistical method with significance level of α<0.05.

Results showed that in scoliosis group, the peak power absorption of the right knee was significantly 12.5% smaller than that in control group (p=0.01). But, peak power generation and absorption of the hip and ankle joints in both right and left limbs were not statistically differed between the two groups (p>0.05).

scoliosis is associated with the smaller power absorption of the knee joint at convex side. This might be linked with unilateral alterations of the jointschr('39') moment, joint forces, and the related muscle activity which might impose asymmetrical force to the hip and cause curve progression.

The purpose of this article is to biomechanically simulate athletechr('39')s leg and compression garment to measure the pressure on a young athletechr('39')s leg in order to apply more optimal and uniform pressure distribution while providing a greater sense of comfort when wearing. The body condition and body shape of the athlete are measured by anthropometric method. Although Using a CT scan of the athletechr('39')s body (athletechr('39')s limb) and the mechanical properties of the pressure garment (leggings) that made of elastane spacer fabric was simulated by finite element technique. The results of measuring the real pressure on the young athletechr('39')s foot were measured and compared by a kikuhime device. The values of pressure applied by the leg in the real state and simulation indicate a maximum error of 14/44 percent (Cross section below the knee and the point behind the leg), a minimum error of 8 percent (Cross section of the ankle and the front point of the leg). Despite the assumptions and sources of error in this simulation, the results show that measured pressure values in the simulation mode with the real mode with incredible accuracy

The aim of this study was to investigate the effect of 8-weeks of resistance training and vitamin D supplementation on some indicators of renal function in male rats with renal failure. Methods In this experimental study, 16 male rats (7-8 weeks and mean weight: 350 to 370 gr) were divided into four groups (n = 4): training, supplement, training and supplement and control group. After induction of kidney damage through NX 5.6 surgical method and two weeks later, resistance training was performed for 8 weeks. Simultaneously, 1000 unit of vitamin D per week intramuscularly was injected. Finally, glomerular purification (using urea and creatinine levels) and serum levels of vitamin D, calcium and phosphorus were measured. Descriptive statistics, one-way ANOVA test and Tukey post hoc test were used to analyze the data. The results showed that glomerular filtration and vitamin D in the training and supplementation groups showed a significant increase compared to the control and training groups (P<0.05). However, Urea and creatinine and serum calcium and phosphorus significantly was decreased (P<0.05). It seems that the simultaneous use of resistance training and vitamin D supplementation can affect glomerular filtration rate.