## 1 Introduction  
Measurements of muscle torque taken in isometric and isokinetic conditions have often been used for sports training [1; 2; 3; 4; 5]. Coaches use biomechanical measurement tools to analyse the sports skill level of athletes, improve movement techniques, or adjust tactics against the opponent [6; 7]. Biomechanical analysis provides a fast and reliable evaluation of torque values, helps detect muscle strength imbalance, and screens for lower extremity injury [8; 9]. Numerous studies have focused on the evaluation of the value of muscle torque in relation to lower limbs, which are particularly involved during sports movements. Appropriate force and proportion between antagonistic muscle groups are essential for optimal or maximum performance of various movements, which is also true in team sport games [10; 11; 12; 13; 14]. The dependence of force on the transverse cross-sectional area of muscles is known, but it should be noted that force is also affected by other factors related to the efficiency of the nervous system (that controls muscle function) and the properties of the muscles themselves [15]. Soccer is a sport in which the requirements for effective play are multi-factorial. The intervals and repetitive nature of the efforts during the match mean that the competitors should demonstrate adequate speed, endurance, strength, and coordination levels. In general, the players do not reach the highest levels of all these motor abilities. However, they must demonstrate a sufficiently high level of preparation in all aspects of motor abilities, with the dominance of some of them (depending on their playing position). Interindividual differences can also be observed in the anthropometric characteristics of soccer players [16]. In soccer, the lower limbs are particularly involved when kicking the ball, striking at a goal, and running at different velocities and with directional changes [17; 18; 19; 20]. Soccer training is aimed, among other things, at increasing muscle mass and, consequently, muscle force. The adequate level of force of the knee extensors and flexors allows the player to achieve stronger strikes, jump higher, and sprint faster over short distances [21; 22; 23]. In addition to the absolute values of the generated torque, the correct ratio of the torque of extensors to that of flexors is also important. The commonly used conventional hamstring-to-quadriceps ratio (H/Q ratio) represents the ratio of concentric hamstring peak torque during lower limb flexion to concentric quadriceps peak torque during lower limb extension [24]. The functional hamstring-to-quadriceps ratio, in contrast, is a measure of the isokinetic eccentric peak torque of the hamstrings relative to the isokinetic concentric peak torque of the quadriceps during lower limb extension at equivalent angular velocities [25]. An adequately high value of these indexes is likely to effectively prevent injuries of the lower limbs (including those that occur without contact) due to effective eccentric activity to slow down or stop the movement [26]. Measurements of muscle torque under isometric conditions allow for the determination of the maximum values of force generated by a given muscle group to evaluate the potential of the player, the training programme, and muscle imbalance. It should also be noted that the amount of force generated depends on many factors, including physiological and biochemical factors. The aspect of morphological determinants is also important. Previous studies have investigated the relationships of muscle torque with body mass, body mass composition, and somatotype [27; 28; 29; 30; 31]. However, the results of such studies have been inconclusive. [PERSON] and [PERSON] [31] demonstrated positive relationships between muscle torque in the knee joint and body mass, fat-free mass, and body fat. Similar results were presented by [PERSON] et al. [27]. [PERSON] et al.