Razi Journal of Medical Sciences

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Background: Most sports require strength and endurance, and maximum strength affects both of these factors. In fact, the rate of recall and the speed of activation of motor units increase with the use of heavier loads and faster contractions (3). This is also true in the sport of karate. Because the speed of implementation of techniques and tactics in the sport of karate is very important and decisive at the professional level and is considered an important step in the success of their struggles. In the meantime, the Giakozuki Chudan technique is the first and simplest hand technique in combat. To score a hit, he must hit the opponent's chest and abdomen with maximum speed (4). In general, improving athletic performance is an issue that athletes have always faced. For this reason, it is common in men to use commercial supplements and do heavy resistance training to increase muscle mass with the goal of improving proper physical appearance, competition success, or gaining strength (6). Nitric oxide is a signaling molecule that contributes to a number of physiological factors, including mitochondrial and biological respiration, muscle glucose uptake, angiogenesis, and cell calcium regulation. Also, increasing plasma nitrite levels through dietary nitrate increases endurance and performance among athletes (8). Nitrate also affects skeletal muscle contraction and mitochondrial efficiency, glucose homeostasis, and respiration (10). Research has shown that nitrate increases lower extremity blood flow during exercise in rats and directs blood flow to type II muscle fibers. Human studies also suggest that nitrate supplementation can increase explosive force production and maximize voluntary force generation in knee blasting (11).
Considering the above and since training causes the comprehensive development of endurance, strength, speed, flexibility and, and considering that in karate the coordination of different body parts and fast and regular movements are very important, the researcher seeks to answer The question is whether the effect of 8 weeks of special strength training with nitrate supplementation has an effect on the speed of Zukki's hand and the strength of Karateka men's hands.
Methods: The present study was a quasi-experimental study with a pretest-posttest design with 3 experimental groups and a control group. To conduct this research, among the karatekas of selected teams in Tehran province in the age range of 22 to 28 years and 3 years of regular karate practice, 40 people were randomly selected and divided into 4 groups: control, strength training, nitrate supplementation and training. And nitrate supplements were divided. Then, 24 hours before the start of the exercises and immediately after the end of the exercises, the desired tests were performed to collect data. The exercises were performed in such a way that first the maximum strength of the subjects was obtained using the 1RM test by McGuigan et al. (1997) in all movements (12). Then, the strength training program was performed in such a way that the subjects practiced their exercises in the evening in 6 movements: chest press, forearm, back arm, leg press, back thigh and front thigh for 8 weeks, 3 sessions per week and Each session performed exercises for 45 to 60 minutes using a dual pyramid method. As the training load increased from 80% to 95% and decreased to 80% again in three sets, the number of repetitions decreased and then increased in proportion to the load (13). Once every two weeks, 1RM test was taken from the subjects and a new program was given to the subjects to observe the principle of overload. In the exercise and nitrate supplement group, in addition to strength training, the subjects consumed one capsule of nitrate at the rate of 5.5 mmol per day with fruit juice (15). The supplement group also used only nitrate supplement. The control group did not exercise and used a placebo. Finally, from the descriptive statistics, Shepherwillek test to check the normality of data distribution and one-way analysis of variance and Tukey post hoc tests using SPSS 21 software at a significance level of 0.05 for data analysis.
Results: The results showed that 8 weeks of strength training with nitrate supplementation on Zouki hand stroke speed (F = 29.896, P = 0.001), hand strength (F = 60.647, P = 0.001), upper body muscle strength (F = 1772.540, P = 0.001) And lower body muscle strength (F = 230.62, P = 0.001) had a significant effect on karateka men. Also, the results of Tukey test showed that there is a significant difference between the control group with the training group, the control group with the training and supplement group, the training group with the supplement group and the supplement group with the training and supplement group, but between the control group and the supplement group. There is no significant difference between the exercise group and the exercise and supplement groups (Tables 1 to 4).
Conclusiom: Regarding the effect of strength training on Zouki's hand speed, it can be said that resistance training is an important part of the training program in most sports by increasing muscle strength, strength, speed, hypertrophy, muscular endurance, motor performance, balance and Coordination plays an important role in improving athletic performance. To achieve these goals in a strength training program, it is necessary to design a proper training program (17). On the other hand, fast performance is one of the salient features of elite karate. Therefore, good performance in karate depends on speed and agility. Due to the nature of karate, the speed of hand movement and the speed of foot movement are the most important factors for good performance (18).
Regarding the effect of strength training on hand strength and upper and lower body muscle strength, it can be said that resistance training usually increases the synthesis of myofibrillar proteins, which leads to increased muscle hypertrophy, especially in type 2 fibers (19). On the other hand, strength is closely related to type 2 fibers and hypertrophy. This may be the reason for the findings of the present study. Regarding the effect of nitrate supplementation on the strength of upper and lower torso muscles, we can mention the mechanism of the effect of nitrate on NO production. Nitrite and nitrate, which are products of NO metabolism; They also act as a NO reservoir (24). On the other hand, studies show the role of NO in regulating neurogenesis in the hippocampus. Neurogenesis is the process by which new nerve cells are produced during fetal development (25). Nitrate may increase the recall of more rapidly contracting muscle units by producing NO and affecting neurogenesis, thereby increasing muscle strength.
Generally in skeletal muscle, high levels of Nnos are present to contract muscle and control blood flow to the area. Skeletal muscles have the micro nitric oxide synthase isoform. NO is produced in contractile muscles and by activating soluble guanylyl cyclase, it dilates the smooth muscles of the vascular wall (26). This makes available enough energy for muscle contraction, which may be the main reason for the present study.
 

Keywords: strength training, nitrate supplementation, zucchini hand speed, hand strength, karate men.

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