Showing 7 results for Shirzad
Dr Elham Shirzad, Dr Ali Asghar Ravasi, Mojtaba Eshrestaghi,
Volume 13, Issue 9 (4-2015)
Abstract
Stiffness is an index for determination of elastic properties of body and its optimum range is different in various
motion patterns. The Spring-mass model is used for calculating stiffness. In this method, the whole leg is modeled
with a linear simple spring. The aim of this study is determination of lower body stiffness and evaluation of its
correlation with agility, as dominant motion pattern in racket sports. 12 national-level male racket-players (age:
25±4 years & weight: 80±7 kg) participated voluntarily in this study. Leg and vertical stiffness were measured
during running on treadmill and hopping test. Pearson’s correlation coefficients were used to examine the
relationships between stiffness and agility test records. Statistical significance was set at P< 0.05. There wasn’t
significant correlation with agility in this study. The reason could be of the contrast influence of knee and ankle
stiffness on performance. This problem requires separate evaluation of joint stiffness.
Mr Mojtaba Ashrostaghi, Dr Elham Shirzad,
Volume 13, Issue 10 (10-2015)
Abstract
Take-off is the critical phase of the long jump event. The aim of this study was to explore the relationships
between different variables and success in take-off. 37 trials performed by 8 long jumper, participants in
fourth indoor Asian senior athletics championships held in Tehran, with personal best average of 7.68±0.28
meter were recorded at 300 Hz. Five speed-related, five technical and four strength-related variables as well
as an anthropometric variable were measured using motion analysis software. More gain in vertical velocity
and less loss of horizontal velocity are considered as two criteria of take-off success and their relationships
with other variables were determined through correlation and regression analysis. Significant level of 0.05
was set. Some variables of all four groups were significantly correlated with success criteria. These variables
along with some others were entered in regression equations. The results emphasized on dominant role of
the technique and approach velocity and represented the effect of anthropometric characteristics on success
in takeoff. Furthermore eccentric strength of knee extensors was shown as the main strength factor in this
performance.
N Shaterkazemi, Sh Zandi, E Shirzad,
Volume 18, Issue 19 (7-2020)
Abstract
Regarding the effects of the kinematics of the movement on athletic performance and the Importance of promoting athlete’s performance on the sport fields, there is limited knowledge about the mechanism of the effect of different variables of volleyball spike. Therefore, the aim of this study was the prediction of jump performance in elite female volleyball players with selected kinematic variables. Thirty elite female volleyball players with mean age of 21.44±3.42 have volunteered for this study. Lower limbs kinematics have been recorded using 16 reflexive markers with Vicon motion analysis system during volleyball spike jump performance. Jump height and time of concentric phase of jump have been predicted by center of mas velocity during step, final step length and ranges of the motion of hip, knee and ankle with stepwise regression (α≤0.05). The results showed that knee range of motion center of mass velocity and step length could be the predictors for time of jump and center of mass velocity and hip range of motion could be the predictors for the jump height as well. Considering these results and the goal and situation of the volleyball match, the players should focus on different phases and affecting variables of the spike jump.
, , Elham Shirzad,
Volume 19, Issue 21 (9-2021)
Abstract
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.
Ghazal Mohammad Gholipour Aghdam, Dr Mohammad Hossein Alizadeh, Dr Hooman Minoonejad, Dr Elham Shirzad,
Volume 20, Issue 24 (3-2023)
Abstract
Neurocognitive motor tasks have been shown to have an effective relationship with athletic performance and musculoskeletal injuries. Cognitive changes following anterior cruciate ligament reconstruction surgery may lead to adverse knee biomechanical changes and an increased risk of secondary injury. This study aimed to compare the kinetics of athletes with a history of ACL reconstruction and those without injuries. A total of 30 professional male soccer players, comprising 15 anterior cruciate ligament reconstruction athletes who had returned to the performance and 15 healthy athletes, participated in this study. The subjects performed at least 5 drop landings with cognitive intervention to decide the landing point on the force plate. The maximum ground reaction force, time to stability and center of pressure with length of path index were calculated at the moment of landing. The Mann-Whitney U test was used to compare the variables. The results indicated a significant difference in four variables: the maximum mean vertical ground reaction force in all landings (p = 0.04), the maximum mean vertical ground reaction force in the best landings (p = 0.01), the maximum average vertical ground reaction force in all landings (p = 0.01), and the maximum mean mediolateral ground reaction force in the best landings (p = 0.03). However, no statistical significance was observed in the variable of maximum time to stability in all landing classes (p > 0.05).The study findings suggest that impaired decision-making with cognitive interference during the flight phase may increase the risk of re-injury in individuals with anterior cruciate ligament reconstruction.
Mr Masoud Sebyani, Dr Hooman Minoonejad, Dr Elham Shirzad, Dr Mohammadhossein Alizadeh,
Volume 21, Issue 25 (9-2023)
Abstract
The Prone Hip Extension test (PHE) is used to evaluate the quality of motor control in the lumbopelvic region. Because of the similarity of this test to the walking and running pattern, it seems that muscle interaction in this test is important in hamstring injury. Therefore, this study aimed to investigate the effect of changing the activation patterns of muscles in prone hip extension on kinematical variables affecting hamstring injury. 28 male soccer players participated in this study. The prone hip extension test was used to evaluate and classify subjects, and based on the activation pattern, they were divided into two groups: normal pattern (N=14) and altered pattern (N=14). We used the Myon electromyography device to evaluate the prone hip extension test muscles activation pattern. Also, the kinematic evaluation of running was done on a treadmill at a speed of 20 km/h. Two-dimensional and three-dimensional video analyses were used to extract kinematic data (pelvic tilt, trunk lateral flexion, and trunk flexion). The range of motion in a running cycle and the amount of each variable at the moment of initial foot contact were used. An Independent t-test was used to analyze the data. The results of this research showed that there is a significant difference in the amount of trunk lateral flexion (p= 0/002), and trunk flexion (p= 0/024) at the moment of the initial foot contact and the range of motion of trunk lateral flexion (p=0/019), and trunk flexion (p=0/035) and pelvic tilt (p=0/008) in a running cycle between the changed pattern group and the normal group. The results of this research showed that changing the pattern of muscle activation in the prone hip extension test can increase the risk of a hamstring injury.
Fatima Riyahi, Heydar Sadeghi, Elham Shirzad,
Volume 22, Issue 27 (8-2024)
Abstract
The fencing lunge is one of the most common and fundamental attacking moves in fencing. The aim of this study was to provide kinematical compare of upper extremity among elite female and male senior fencers when performing a lunge. Four female and four male members of Iran National Team were selected as research sample. The participants were filmed when performing a complete lunge with a camera of 300 Hz sampling rate to evaluate kinematical parameters. The student's-t test revealed that elite male fencers had significantly shorter reaction and movement time comparing with elite female fencers. No major differences in other kinematic parameters indicate that elite male and female fencers performed lunge in similar way. The final conclusion of this study is that the existing differences in time of lunge technique may suggest the need for alternative training strategies to prepare fencing athletes.The examination of the kinematic analysis of the upper body in male and female elite fencers demonstrated that the dissimilarity in the execution speed of the lunge technique between the two genders cannot be accounted for by kinematic changes in joint movements. The differences highlighted in this study can serve as a basis for formulating distinct training and coaching strategies, with the aim of better preparing athletes for decision making and quick movements.
