جستجوی مقالات مرتبط با کلیدواژه « force » در نشریات گروه « پزشکی »

The successful performance of block skills is crucial for volleyball players, requiring efficient techniques that optimize time, movement, and vertical jump. The purpose of the present investigation was to compare the kinetic temporal phasic differences between middle and side blockers among elite volleyball players during block jump. 

Seventeen junior male volleyball players, consisting of eight middle blockers and nine side blockers, participated in this research. The evaluated skill was the block jump ability. Data collection involved calibrating a force plate (Kistler® 1000 Hz). An independent t-test was used to compare mean values between the two groups during jumping (p<0.05). 

The results indicated no significant differences between middle and side blockers in terms of time and force during the amortization phase. 

These findings provide valuable insights into monitoring time and force variables among middle and lateral blockers. Trainers can utilize these results to tailor task-specific training programs that optimize performance outcomes.

 shoulder muscle fatigue in exercise is very common among bodybuilders. Fatigue can lowers the performance quality and seriously damage athletes’ shoulder joints. This study aimed to determine the effect of fatigue on the force of flexor, extensor, elevator, depressor, retractor, and abductor shoulder muscles in young bodybuilders after a session of debilitating fatigue. 

 In this quasi-experimental study with a pre-test and post-test design, 25 active athletes in the field of bodybuilding (age: 26.12±2.78 years, height: 1.82±0.035 m, weight: 78.92±4.23 kg, BMI: 23.71±1.40 kg / m2, and sport history: 2.96±0.97 years) were selected. Before and after the fatigue, the force of flexor, extensor, elevator, depressor, retractor, and abductor muscles of shoulder was evaluated using a portable tensile-compression tachometer. To analyze the statistical part, the paired samples t-test was used to compare the fatigue protocol. 

 The results of the study showed a reprise of debilitating fatigue reduced the force of flexor (P=0.001), extensor (P=0.001), elevator (P=0.001), depressor (P=0.001), retractor (P=0.001), and abductor (P=0.001) of shoulder muscles. 

 In general, the results of the present study showed the effect of fatigue on the reduction of flexor, extensor, elevator, depressor, retractor and abductor muscles of the shoulder, and this force decrease can be a factor for reducing performance quality in fatigue conditions and probably increasing the risk of injury in athletes.

Using minimally invasive neurosurgical robots is one of the most desirable ablation methods and resection of brain tumors. In this study, forward kinematics and Jacobian matrix calculated for two single-port robots for comparing the effectiveness of two types of single port minimal invasive surgical robots to ablation and resection of brain tumor

The motion analysis of robots type 1 and 2 has compared to each other. Ablation manipulator in robot type 1 has five degrees of freedom, but in robot type 2, three revolute degrees of freedom of this manipulator has replaced with a revolute joint perpendicular to the previous three revolute joints.

Results showed that for resection surgery, in the same conditions, robot type 2 damaged 58.9 mm3 more of cerebral cortex tissue than robot type 1 to resect the brain tumors. To establish a static balance, robot type 2 needs to tolerate at least 41% more internal loading than robot type 1. The maximum velocity for robot type 1 in the contact location between the end-effector and the tumor is 1.7 times more than robot type 2. The maximum end-effector force of robot type 1 to apply the tumor for ablation surgery is more than 1.8 times in robot type 2, but the maximum moment and power for ablation surgery and resection of these two robots were the same less than 1% difference.

Despite the more straightforward mechanism, a minimum number of joints, and better kinematics range of robot type 2, robot types 1 has the possibility for transformation, establishes the static balancing, and does a better ablation surgery with less damage to the brain.

Muscle fascicle length and pennation angle are two muscle structural parameters which can be non-invasively measured using methods like ultrasonography. The aim of the present literature review was to introduce fascicle length and pennation angle for the estimation of the force of an individual skeletal muscle using ultrasonography.

Methods and Materials:

 The data for the current review study was obtained from Pubmed, Science Direct, Scopous, Google Scholar, Sprinter Link Database, and other authoritative references available on the Internet and in libraries between the years 1995-2015. A total number of 113 articles were obtained. In sum, 45 articles were collected and reviewed. Keywords such as muscle, fascicle, length, angle, force, and ultrasonography were searched to fulfill the purpose of the study.

Detailed information on the pennation angle and fascicle length is essential to predict the force of an individual muscle. It has been suggested that changes in muscle fascicle angle and length correlated variably with the muscles force production.

Real-time ultrasonography has been introduced as a valuable measurement tool for estimation of the force individual muscle via measuring the muscle architecture parameters, such as pennation angle and fascicle length. However, factors like physiological, anatomical, and biomechanical properties have to be considered when predicting the force of an individual skeletal muscle.