## 4 Discussion
Faster neural adaptations during eccentric contractions involve an inverse motor unit activation pattern. [PERSON] [58] highlighted a greater cross-transfer of strength with an eccentric phase (47%)versus concentric phase (28%) loading group. One of the possible reasons for the greater effect of eccentric loading was a larger increase in corticospinal excitability, which has been proposed as the mechanism underlying this effect [59]. All exercises used in the experiment were based on the SSC (stretch-shortening cycle). During concentric contractions (CON), the force that muscles generate is always lower than the maximum voluntary isometric contraction, because the load that the muscles must overcome decreases and the speed of contraction increases. This process depends on the moment at which the muscles reach their maximum contraction velocity, (V\({}_{\text{max}}\)). When the speed of contraction is negative (the muscle lengthens), the muscles contract eccentrically. For eccentric contractions (ECC) of a muscle, the force-velocity relationship is significantly different from the CON contraction. Supramaximal muscle strength can be generated at both slow and fast contraction speeds. This creates a method of training with high loads at high speeds, which is impossible to achieve with CON contractions according to the force-velocity relationship. During active stretching, human muscle fibers produce 1.4 to 2.1 times the tension (force produced per cross-sectional area of the muscle) depending on the type of fiber [60]. A rapid or explosive tempo is typically used to improve maximal power. Despite the small number of studies considering the effects of different TUTs on peak power, it can be pointed out that faster tempos are more effective in developing power. However, the biomechanical demands for particular limbs change with the weight being lifted and depend to some extent on the role that the joint plays in the movement. This process is also influenced by the individual potential of the athlete [10]. This fact changes the concepts of periodization of strength and power training. Therefore, in order to develop power, a fast or explosive TUT of movement is recommended, but to optimize movement at particular joints, a combination of external loads based on different percentages of 1 RM may be recommended. The available data on the effects of different movement tempos on power refer to chronic changes, and only one study considered the acute effects of movement tempo on power. This study found that a faster eccentric tempo (2/0/X/0 - X determines maximum velocity) during the bench press exercise generated greater power levels and higher bar speed in a concentric movement compared to a slower eccentric tempo (6/0/X/0). Therefore, this study shows that the time of eccentric movements has a significant impact on power output and barbell speed of central movements [56; 61]. However, when comparing both forms of the UNI and BIL mesocyte to the obtained results, they were equally effective except for power output during knee flexion, where unilateral training contributed to improvement, whereas bilateral training did not. However, the effect size was larger after unilateral training in each variable tested. It is worth referring to the work of [PERSON] et al. [62], which pointed out that the most appropriate TUT for strength gains is between 2 and 20 s per set, while [PERSON] et al. [63] concluded that RT performed not until failure may induce comparable or even greater improvements in maximal dynamic strength and power output. He pointed out that the completion of a maximum concentric repetition of resistance exercises at a particular load could result in greater improvement of maximum strength and power than a relatively slow repetition at a slower tempo with fewer repetitions [64]. This is contrary to our results because, during the peak accumulation phase, TUT was 50 s for the BIL exercise and 100 s for ones (50 s per limb). However, attention should be paid to the maximum concentric phase in each of our microcycles.