Effect of Eight Weeks Plyometric Training on Some Kinematic Parameters, Hori- zontal Jumping Power, Agility, and Body Composition in Elite Parkour Athletes

* Corresponding Author: Abdolrasoul Daneshjoo, PhD. Address: Department of Sport Biomechanics and Corrective Exercise, East Tehran Branch, Islamic Azad University, Tehran, Iran. Tel: +98 (21) 33585909 E-mail: phdanesh@yahoo.com 1. Department of Sport Biomechanics and Corrective Exercise, East Tehran Branch, Islamic Azad University, Tehran, Iran. 2. Department of Sport Injuries and Corrective Exercise, East Tehran Branch, Islamic Azad University, Tehran, Iran. *Abdolrasoul Daneshjoo1 , Soudabeh Raeisi2


Introduction
arkour is an activity involving movement through obstacles in the fastest possible time using the easiest and simplest method with the least energy consumption from one point to other [1]. These plyomet-P ric exercises enable the muscles to reach their maximum strength in the shortest possible time. They put a lot of pressure on the athlete's neuromuscular system and joints in a short period of time; if these exercises be performed without a proper and accurate program, they can cause severe damage to the joints and muscles [2].
Due to the high extrinsic contraction, which is a major component in plyometrics, Delayed Onset Muscle Sore-ness (DOMS) is experienced steadily, especially in the early stages of pre-adaptation program. However, plyometric exercises have become commonplace and have always been an important element of exercise programs to increase an athlete's strength [2]. Other studies that have used plyometric exercises have also shown improvements in torque [3,4]. The basis of parkour is jumping and running, and due to the ability of plyometric exercises to convert strength into explosive force, these exercises may be effective in parkour performance in [4]. This study aimed to examine the effects of an 8-week plyometric exercise program on kinematic parameters, body composition, agility and horizontal jump of elite parkour athletes in Tehran.

Methods
This is an applied quasi-experimental study using the field and laboratory tests. The study population consists of male parkour athletes in Tehran, Iran aged 19-26 years with at least 4 years of professional experience. Among the eligible volunteers, 20 who did not have any acute or chronic disease were selected as the study samples using G-Power software and were randomly assigned to training and control groups. Prior to the study, all subjects signed the consent form to participate in the tests and then, during a session, the subjects were explained how to perform the tests.
Kinematic parameters of the knee were measured using Navicular Drop Test, Tibial Torsion Test, Q-angle test, an-

Results
According to the normality of data related to horizontal jumping power, agility, body fat percentage, body weight and Body Mass Index (BMI), which was determined by Kolmogorov-Smirnov test, paired t test was used to compare them. For comparing knee kinematic parameters, independent t-test was used. The results are presented in Table 1.

Conclusion
According to the sport of parkour, i.e. jumping through obstacles, the performance in parkour can exponentially be improved by increasing the jumping power. For this reason, the main goal of all exercises is to improve the jumping ability. Horizontal jumping power is measured by standing broad jump test and jumping is one of the main movements of parkour [5].according to Ozbar et al., Ramírez-Campillo et al., and Imani et al., plyometric exercises can increase strength and agility, and Parkour exercise makes horizontal jumping better and more powerful [6][7][8]. Concentric strength and stiffness of the biceps muscles in the back of the hip, which are hip extensor and knee flexor, can increase the rate of concentric contraction during hip extension and knee flexion. This function, combined with the high eccentric power of the knee extensors which prevents excessive flexion and center of mass fall, can increase vertical velocity and decrease horizontal velocity, which is desirable for a successful jump. In our study, the 8-week plyometric exercise program significantly reduced body fat percentage Short limb length causes the pronation of the shortened limb. The difference in apparent length indicates the nonstructural difference between the two sides. One common cause of this discrepancy is the apparent short length of the hip adductor and abductor muscles in one side. The apparent difference in the length of the legs over time is due to the repetitive performance of regular activities. Work or exercise habits make one side of the spine stronger than the other.