## 4 Discussion  
Overall, the analysis showed that the training sessions were equally effective. Only in terms of power during the knee flexion, unilateral training contributed to improvement, whereas bilateral training did not. However, the effect size was larger after unilateral training in each variable tested (Tables 5 and 6). Comprehensive training requirements resulting from the specificity of a given discipline require proper periodization of resistance training. Therefore, the present study investigated the effects of a periodized training mesocycle using step load progression during unilateral and bilateral training on the level of peak torque and power of lower limb extensors and flexors. The results of the experiment showed that the UNI mesocycle was more effective in developing peak torque and power of lower limb extensors and flexors. Appropriate modeling of resistance training, depending on its purpose, induces various types of morphological and neural adaptations, which are a direct consequence of this process [43; 44; 45; 46]. Our mesocycle consisted of four training microcyles, which were conditioned by the team's preseason which consisted of five mesocycles. The first 10-day microcycle included two resistance training sessions for neuromuscular adaptations and four 7-day microcyles (two training sessions per microcycle) with the use of a 3:1 step load distribution in order to achieve neuromuscular supercompensation before the start of the competitions. Both the UNI and BIL groups performed exercises mainly for the lower part of the body, which results from the specificity of the discipline, and several exercises for the upper body. The step load was selected based on a modified non-linear or \"undulating\" periodization model (Figure 1) [47]. The main training variables were pace and time under tension, which are part of the training volume according to [PERSON] et al. [6]. However, the entire intensity of the mesocycle was constant and was determined during each training session using  
Figure 3: (**a**) Inter-individual responses to the unilateral (unfilled circle) and bilateral (filled circle) training intervention in the knee flexion symmetry index in relation to relative peak torque. (**b**) Inter-individual responses to the unilateral (unfilled circle) and bilateral (filled circle) training intervention in the knee flexion symmetry index in relation to relative peak power. Velocity Based Training (VBT) corresponding to (1-0.75 m/s), which is equal to 50-60% of 1 RM (Table 1) [48]. Because using an athlete's previous maximum capacity to determine training loads may be problematic if the athlete's 1 RM changes as a result of training adaptations, the prescribed load may not match the % of 1 RM intended for a given training session. Additionally, each player may react differently to the main soccer training sessions, especially in the preseason, which may result in variable loads (kg) at which the players will generate appropriate power (1-0.75 m/s). Another fact is that the number of repetitions that can be performed at a given % of 1 RM varies among athletes; therefore, assigning all athletes the same number of sets and repetitions may result in different levels of effort and fatigue [48]. In our research, athletes during the 4-week UNI and BIL mesocycle were equally effective even though the load from VBT corresponds to 50-60% of 1 RM (Tables 2 and 3). This is contrary to the research of [PERSON] et al. [49] where it was shown that trained non-athletes during resistance training effectively develop maximum strength with a mean training intensity of 80% of 1 RM, 2 days per week, and a mean volume of four sets. This work also showed that for untrained people, maximum strength gains are achieved at an average training intensity of 60% 1 RM), 3 days per week, and an average training volume of four sets per muscle group. For athletes, maximal strength gains are elicited at a mean training intensity of 85% of 1 RM, 2 days per week, and with a mean training volume of eight sets per muscle group.