1. Introduction
In volleyball, athletes change their body position and orientation to interact with the ball. The result of interaction depends on how the player contacts the ball, the speed of the ball (size and direction of contact), and the mechanical properties of volleyball. Collisions occur at low to high velocity during service or after an attack. The ball material may affect the ability of athletes to maintain the ball in these conditions [1]. Different models of sports balls had used during training and competitions. The difference in COR between the balls can affect the amount of force a player must apply to a particular ball. As a result, understanding the mechanical behavior of different volleyballs when colliding may be helpful for coaches and athletes [1].
The mechanical properties of volleyballs may affect the risk of injury. When a volleyball hits an athlete’s body, forces and energies had transferred to anatomical structures, including skin, muscles, tendons, ligaments, and bones. These may lead to sports injury, so the mechanical properties of volleyballs, especially the stiffness of the ball to reduce the forces on the limbs of athletes, can play a role in causing injury [1, 2]. Therefore, this study aimed to compare the impetus of new beta volleyball designed with other volleyballs available to reduce the rate of sports injuries in volleyball athletes.
2. Method
Samples of Mikasa volleyballs model V200W made in Japan, Fox volleyballs model Spain made in France, and old and new BETA volleyballs made in Iran with a weight range of 260 to 270 grams with a circumference of 66 cm had used in the present study. The balls had compared using the Bertek impulse model force plate device. Descriptive and inferential statistics had used to analyze the obtained data using SPSS software version 26 with a significance level of P≥0.05. The normality of data distribution had determined by the Shapiro-Wilk test. One-way analysis of variance and LSD post hoc test was used to see a difference between the groups.
3. Results
Based on Table 1, the results showed: Deformity of all four volleyball samples after leaving the impact test machine had no significant difference between the four groups in terms of deformity (P=0.85).


There was no statistically significant difference between the new BETA volleyball design mutations compared to the samples in the study (P=0.55). In other words,  the deformity and mutation of all four volleyball samples to enter the present research are close according to the tests performed and met the standards set by the Fédération Internationale de Volleyball (FIVB). There was no significant difference in terms of deformity and mutation.
This study showed no statistically significant difference between the impulse of the new beta volleyball sample with the old beta volleyball sample and the Fox and Mikasa volleyballs in the direction of the vertical axis (P=0.053).
In this regard, the post hoc test showed a statistically significant difference between the impulse of the new BETA volleyball design compared to the old BETA volleyball designed in the vertical axis (P=0.014). There is no significant difference between the sample of the new BETA volleyball compared to the sample of Fox volleyball (P=0.102) and Mikasa volleyball (P=0.662) which is used in official competitions.
4. Discussion
Based on the research, few studies had done on material and impulse calculation in sports balls. In 2014, Koizumi et al. examined the impulse force of modern soccer balls designed by Adidas, including the new football balls Jabloni, Kafusa, Tim Gist, and Pilist. An impact robot equipped with a dynamometer had used to measure the momentum during impact. They reported significant differences between the impulses of different types of footballs, which is in line with the present study results. The differences in the balls can be related to the structure and material used in each of the samples [3].
Also, a reason for this discrepancy could be related to the flexibility of the surface material and the structural characteristics of each ball. This study results showed no statistically significant difference between the mutation, deformity, air pressure, and weight of the new volleyball designed with the old Beta volleyball models, Fox and Mikasa. In the third layer of the ball, the use of fabric instead of rubber did not affect the jump, deformity, air pressure, weight of the balls, and other values. In other words, all four volleyballs were the same in terms of mutation, deformation, air pressure, and weight and met the standards set by the Fédération Internationale de Volleyball (FIVB).
In line with the results of this study, in 2018, Lauren et al., in a study using the American-made Bertek model power plate device, measured the forces acting on the plate. They used the contact time between the ball and the force plate for each stroke to estimate the stiffness of the ball. Their research results showed a positive relationship between the stiffness and speed of impact between different types of volleyballs. They considered the forces involved when volleyballs hit the athletes’ limbs to discover the mechanisms of injury and the design of new volleyballs to increase the safety of volleyball athletes [1].
The results of this study are almost consistent with the results of Bilika et al. (2018), who studied the elastic details of a volleyball and its air pressure during research. They hit the volleyballs on the hard surface. Their results show that the distance traveled in the total number of strokes depends more on the internal pressure.
In this study, the ball’s initial velocity was unchanged, and only the internal pressures were the same in all balls. In general, it can be concluded the same initial velocity of the ball can lead to the same air pressure inside the volleyball does not change [4]. The use of the new beta volleyball designed to reduce the rate of sports injuries is recommended to all coaches, referees, athletes, and officials in volleyball.

Ethical Considerations
Compliance with ethical guidelines
All ethical principles are considered in this article. Participants were informed about the research objective and its implementation stages. They were also confident that their information would be confidential and that they could leave the study at any time, and that they would be provided with the results of the research if they wished.

Funding
This research was carried out with the financial support of Mohaghegh Ardabili University and Tanin Peyk Sabalan Company (beta sports balls).

Authors' contributions
Basic idea of the article, statistical analysis of data and writing of the article: Mohsen Barghomadi; Idea, initial writing of the article, laboratory work and submission of the article: Ehsan Fakhri; Preliminary writing of the article and statistical analysis of data: Mr. Safa Siraj Mehdizadeh.

Conflicts of interest
The authors declared no conflict of interest.

Acknowledgements
The new volleyball was designed in collaboration with the R&D unit of Tanin Peyk Sabalan Company (Beta Sports Balls), one of the largest manufacturers of sports balls internationally. Therefore, the cooperation of this company as well as the experts of the Health Center of Mohaghegh Ardabili University, who had the utmost cooperation in the implementation of this research project, is thanked and appreciated.
 

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