###### Abstract  
This study aimed to determine the influence of body composition on the muscle fitness of selected judokas. This study was conducted on a sample of 23 judokas (cadets \(n=12\), juniors \(n=11\)), members of the male national team of Serbia. The assessment of body composition was performed using the InBody 720 (Biospace Co., Ltd., Seoul, Republic of Korea) and calipers. Muscle fitness was assessed using \"Optojump\" (Microgate, Bolzano, Italy), Firdodine Premium (Fitronic, Bratislava, Slovakia), and a digital force instrument IMADA ZEH-1100 (Imada Inc., Northbrook, IL, USA). Regression analysis revealed a notable association between muscle mass and measures of explosive strength (countermovement jump (CM)) \(p=0.023\); drop jump (DJ) \(p=0.026\)). Moreover, this study's results showed that back extension (\(p=0.006\); R\({}^{2}=0.61\)) and hand grip (\(p=0.009\); R\({}^{2}=0.52\)) provide a strong positive association with muscle mass. The findings suggest that tailored training and nutritional strategies that improve muscle mass might significantly enhance muscle fitness in young judokas, optimizing their performance. **2024**
competitive success in judo is influenced by various factors such as muscle strength, endurance, anaerobic power, aerobic capacity, flexibility, and the technical efficiency of judokas [9]. However, these studies often lack specific numerical data and detailed analysis of the physiological profiles of elite judokas, particularly how their body composition relates to fitness components such as strength and agility. This study builds upon these findings by focusing on the associations between body composition and muscle fitness parameters among elite judokas. Strength is one of the most dominant fitness parameters in judo. During a fight, judokas activate a significant portion of their muscle mass in both the upper body and lower extremities. Elite senior judokas are known for their high muscle strength and upper-body muscle endurance, which are critical for executing and resisting throws, maintaining grips, and ensuring quick recovery during a match [1]. Previous studies have indicated that the arm and forearm flexor muscles are crucial due to judo's direct physical contact and gripping actions [10]. Therefore, understanding how muscle mass distribution relates to these strength attributes can provide valuable insights for optimizing training and performance. The body composition of athletes depends on several factors: age, gender, health status, genetic factors, diet, and training process [11]. This implies that the training process could be adjusted if the factors affecting sports performance are clearly defined [12]. The training process of judokas can vary depending on the weight category of the competitors, so systems and training methods are chosen to meet the needs of light, medium, and heavy categories. One way to gain an advantage over the competition is to enter a lighter-weight category by adjusting body weight while aiming to maintain muscle mass and lose body fat [13]. In judo, a growing problem is losing body weight before competing in the desired weight category [14]. Therefore, efforts are made to define the optimal body composition. Consequently, the question arises: what association does body composition have with the muscle fitness of top judokas? It is well established that the mesomorphic somatotype, characterized by a large percentage of muscle mass and a low percentage of body fat, is typical for judokas [15]. Elite judokas should maintain a body fat percentage below 10% through a programmed training process and proper diet [1], except in the heavy and super-heavy categories (up to 100 kg and over 100 kg). Research has shown that Olympic and world medalists have less than 10% body fat [2,16]. While the association between body composition and the strength of top judokas is an important area, it has not been sufficiently researched. This study, therefore, might have practical implications for the fields of sports science and marital arts.