Introduction: An important variable in investigation of agility during puberty is the age of reaching peak high velocity, which like other agility indicators is under the effect of different factors such as physical condition and type. The purpose of present research was to examine relationship between somatotype and peak high velocity (PHV) among Iranian 7-10 years old boys.Methods: Participants were 313 7-10 year-old members of Basij talent identification centers in all Iran's provinces. Somatotype data were calculated using Heath-Cartr instruction and PHV was measured using Mirwald formula and were analyzed using Pearson correlation and multiple regressions.Results: Results of pearson correlation showed that PHV had a positive correlation with ectomorphy and negative correlation with endomrphy and mesomorphy. Total correlation between PHV and somatotype was 0.50 which explained 25% of PHV variance. Results of regression analysis showed ectomrphy and endomorphy were significant predictors of PHV but msomrphy was not a significant predictor of PHV.Conclusion: Endomorphy had a smaller part in predicting the PHV age, but mesomorphy was not a strong predictor, Moreover, ectomorphy following endomrophy had a strong predicting power. Studies in this area suggest that those who have greater ectomorphic characteristics are less agile and the physiologic requisites for their puberty develop later in their bodies. Therefore poor sport performance of ectomorphic children may result from their distance to PHV age so coaches and instructors should consider this measurement and somatotype.

Background: Left atrial appendage contraction velocity (LAAV) is used frequently as a surrogate for global left atrial function, but the validity of this parameter for the prediction of left ventricular systolic and diastolic function has not been evaluated extensively. The objective of this study was to assess the relationship between LAA contraction flow velocity and left ventricular systolic and diastolic function parameters.Methods: This study was performed on 142 patients-62 male (43.5%) and 80 female (56.5%)- who were referred for an evaluation of the source of emboli. Exclusion criteria were significant valvular abnormality, prosthetic valve replacement and congenital-heart disease. Results: The correlation between LAA contraction velocity and systolic ventricular function was significant (p value=0.05). There was an inverse. relation between LAA contraction velocity and LV contraction: in 78 patients with LVEF<50%, mean LAAV was about 29cm/s, while in 64 patients with LVEF>50%, mean LAAV was about 50cm/s. Regarding diastolic flow parameters and pulmonic vein flow, patients were classified into four groups as follows: 1) 76 cases with normal patterns, 2) 38 cases with impaired LV relaxation, 3) 16 cases with pseudo normalization and 4) 12 cases with restrictive patterns. Statistical analysis did not show significant correlation between LAAV and diastolic function (p=0.236). Correlation between diastolic function parameters and LAA contraction velocity revealed a significant relation between LAAV and A wave velocity of mitral inflow (p=0.02) and no significant relation between LAAV and other diastolic parameters including E wave velocity, DT and IVRT (p=0.66, p=0.73, p=0.79). ECG showed 98 cases with normal sinus rhythm (NSR), 9 with complete atrioventricular block (CAVB) and 35 with atrial fibrillation (AF). There was a significant reduction in LAAV in AF rhythm compared to NSR. Conclusion: LAA contraction velocity has a close relation with LV systolic function, but not diastolic function. Therefore, LAA contraction velocity should be considered a surrogate for left ventricular systolic function.

Purpose: Unique activation strategy of eccentric contraction predisposes the muscle to damage. Type II muscle fibers are more susceptible to muscle damage, therefore, it seems that velocity interferes in mechanical stress and muscle damage. The purpose of this study was to investigate the effect of contraction velocity of eccentric exercise-induced muscle damage of dominant knee extensor on running economy in trained young females. Methods: Sixteen trained young females randomly assigned into two groups: high velocity (240° . s-1) and low velocity (60° . s-1). In order to induce muscle damage, subjects in high and low velocity groups performed 20 and 5 sets of 15 eccentric contractions respectively, with a load equal to 150٪ of the maximal voluntary isometric torque (MVIT) of dominant knee extensors. Muscle damage indices (MVC, perceived pain, thigh circumference) were recorded before, 1 and 48 hours and running economy were recorded 24 h before and 48 h after eccentric exercise. Statistical analysis was performed with SPSS16, using the between-subject repeated-measures ANOVA, independent t-test and Mann-Whitney U test. Results: All muscle damage indicators significantly changed one and 48 hours after damage in both groups (p<0. 05) in a way suggestive of muscle damage. There were no significant differences for any of the muscle damage indicators (except perceived pain) and running economy at different running intensity between groups. Conclusion: With regard to the same tension time in muscle, contraction velocity (Four-fold difference) of eccentric exercise-induced muscle damage of dominant knee extensor was not a determining factor of changes in running economy in trained young females.

Pedaling is recognized as one of the most widely used therapies in rehabilitation. Which is influenced by various factors. Studying the effect of saddle position and saddle height (horizontal and vertical distance of saddle from pedal, respectively) changes in the pedaling feasible places range (saddle height range: 49-80% of leg length) on the leg joints range of motion and muscles contraction velocity are the purposes of this study. The pedaling conditions with ergometer are obtained in the model (crank arm length and pedaling rate are 17. 5 cm and 80 rpm, respectively). Results indicate that ankle, knee and hip joints range of motion are 11. 08-37. 54 (SD: 0. 03-1. 86), 69. 61-80. 58 (SD: 4. 02-9. 76) and 42. 89-46. 13 (SD: 0. 07-2. 89), respectively. The effect of saddle height changes on ankle>knee>hip and the effect of saddle position changes on knee>hip>ankle range of motion. By increasing the saddle height, ankle and knee joints range of motion increase significantly. The positive correlation between ankle-knee, ankle-hip and knee-hip joints, show the coordination and the cooperation of joints during cycling. The saddle place changes affect the contraction velocity of lower limb muscles. In particular, by changing the saddle place in the feasible places, the contraction velocity of ankle, knee and biarticular muscle groups change in a wide range.

Background & Objective: Eccentric muscle action is mechanically more efficient but employs a unique activation strategy which predisposes the muscle to damage. Type II muscle fibers are more susceptible than type I fibers to muscle damage; hence, velocity probably interferes with mechanical stress and thus may modulate muscle damage. The purpose of this review study was to investigate the effect of contraction velocity on selected muscle damage indices following acute eccentric exercise-induced muscle damage.Material & Method: Looking up related articles published in valid scientific databases such as PubMed, Springer, Elsevier, Science Direct, and SID with standard keywords and according to the research criteria, 16 studies (1980 to 2015) were selected.Results: Ten studies showed that high velocity eccentric exercise induced greater muscle damage. Five studies showed no differences between velocities, and a single study indicated a greater magnitude of muscle damage following slow eccentric exercise.Conclusion: Thus, greater magnitude of damage is induced by contractions performed at a higher velocity. However, considering differences during tension in the majority of studies, focusing on elbow flexor muscles and muscle damage profile variety in various muscle groups, and more animal and human studies in other muscular groups are necessary to confirm how the velocity of acute eccentric exercise would affect the muscle damage.

In the present study a method for investigation of possibility of detonation in high speed flows based on available experimental data have been described. For this purpose, different kind of important parameters that were needed for possibility of detonation were evaluated. These parameters are included, detonability limit of the mixture and effect of neutral additives, kind of confinement, geometry and dimensions, type of initiation including direct and DDT initiation and special properties of the mixture like, pressure, temperature and velocity. The information and how to use these parameters for analysis of problem was presented. This method is specifically used in discharging of a supersonic jet containing hydrogen in three different modes of operation. the results show the limit area of danger is located 2 to 8 meters in area outlet. On the other hand, considering of experimental data was demonstrated that the presence of water vapor can decrease the possibility of detonation and The maximum permitted percentage of water vapor has been determined about 30% for detonability of the mixture. With considering high percentage of water wapor in the area of danger it is determined that this region is not detonable.

The purpose of velocity analysis is to extract the normal moveout velocity as a function of the zero-offset travel time at selected CDP locations along the seismic line. Since results of velocity analysis depend on coherency estimator, an estimator that provides a high velocity resolution is essential. Even though the conventional semblance method which is the most popular coherency estimator (Tanner and Kohler, 1969) provides a robust velocity spectrum, the tendency to smear the velocity peaks as the time increases makes the estimation of accurate velocity difficult. This estimator, however, has some resolution limits that cause problems in some cases. It fails to distinguish interfering events in a short time window and in cases of thin bedding (Lerner and Cellis, 2007).We propose here two new coherency estimators that resolve these limitations at a minor extra-cost. The estimators are based on a differential semblance (DS) coefficient (Symes and Carazzone, 1991) that is weighted by the semblance estimator. High-resolution is introduced by sorting the traces in the data in a way that highlights the time shifts between adjacent traces within a time gate. The new estimators exploit the redundancy of seismic data in the common mid-point (CMP) to bootstrap the seismic traces in a manner that nicely brings time shifts between adjacent traces to discriminate time gates built using parameters that are close to the true stacking parameters. Bootstrapping is a statistical technique used to infer estimates of standard errors and confidence interval from data samples for which the statistical properties are unattainable via simple means. The first proposed estimator is deterministic bootstrapped differential semblance (BDS) that is based on a deterministic sorting of original offset traces by alternating near and far offsets to achieve maximized time shifts between adjacent traces. Deterministic sorting that alternates near- and far-offset traces in the time window has higher resolution than does simple bootstrapping applied to the data traces. The second was the product of several BDS terms, with the first term being the deterministic BDS defined above. The other terms were generated by random sorting of traces that alternated between near and far offsets in an unpredictable manner. The proposed estimators help in discriminating several trial parameters which produce a good guess of the flattening parameters and have direct implications in retrieving velocity information from time gathers. The suggested estimators are tested on synthetic and real data examples to show the gain in resolution they yield when applied, and they are compared with coefficient semblance. Results show that deterministic BDS coefficient provides an increased resolution with no extra computing effort compared to the BDS coefficient. Further resolution can be achieved by involving several controlled bootstrapping outcomes in the estimator, but this comes at a computing cost nearly proportional to the number of terms in the high resolution estimator.The high-resolution BDS proves to be an efficient tool in building velocity spectra for time-domain velocity analysis and it provides more resolution with respect to conventional semblance estimator. The proposed estimators could be a good substitute for the semblance coefficient, and an economic alternative to other high resolution estimators such as eigenvalue methods that are expensive for the dense parameter tracking in high fold data sets.

Velocity analysis is one of the most important stages of seismic processing. The most conventional method for velocity analysis is to calculate the semblance coefficients. Traditional semblance has some shortcomings, for instance, low resolution in time and velocity direction, high computational cost, and having trouble in presence of amplitude variation-with-offset (AVO) phenomenon. In order to compensate for the latest shortcoming, AB semblance has been proposed. However, this method has approximately twice the lower resolution than traditional semblance. On the other hand, due to effects of the source wavelet, seismic events have band-limited nature, which leads to a decrease in temporal resolution. Recently, the deconvolutive Radon transform has been introduced to overcome the latest problem. In this paper, we have developed the deconvolutive hyperbolic Radon transform for AVO preserved velocity analysis. We have also used the log-polar domain in order to reduce computational cost. We tested this method on both synthetic and real field data sets to show resolution improvement in the proposed method. ...

The conventional velocity analysis sums the amplitudes of events along hyperbolic trajectories and converges the energy in the corresponding intercept time and slowness or velocity. This makes the velocity analysis as one of the most time consuming seismic data processing steps. On the other hand, this algorithm suffers from low resolution due to several reasons. In this paper, we use the Butterfly algorithm to calculate the forward and adjoint operators of the hyperbolic Radon transform in a much faster way, compared to the conventional integration in the time domain. Moreover, by applying it to fast iterative shrinkage-thresholding algorithm (FISTA), a high-resolution velocity panel is obtained.