Discussion
vastus lateralis stiffness
CONTRACTION
The main aim of this study was to compare the effectiveness of bilateral and unilateral drop jumps as a CA on subsequent CMJ performance and sprinting time, as well as inter-limb asymmetry and vastus lateralis stiffness. The main finding of this study was that only B-CA contributed to a significant increase in CMJ height, and RSImod (via a decrease in contraction time). In turn, none of the studied CAs had a significant effect on the 10m sprint time. There were also no significant changes in inter-limb asymmetry or vastus lateralis stiffness during either condition.To the best of the authors’ knowledge, this is the first study that compared the effects of single-legged and double-legged drop jumps as a CA on subsequent CMJ performance and sprinting time. Although the effectiveness of unilateral exercises in inducing the PAPE effect is well researched, possibly only two studies to date have investigated the use of single-legged drop jumps as a CA. Studies by Dello Iacono et al. [However, both DJs performed by the stronger and weaker lower limbs used in this study had no effect on the subsequent CMJ performance. On the other hand, according to previous findings, bilateral DJ as a CA increased CMJ height and reduced contraction time, resulting in improved RSImod [The study included trained athletes, who should have no trouble alternating various exercises and performing them with the highest quality. However, it seems that the obtained results may also be related to the preservation of movement patterns. This may be confirmed by a significant augmentation of the CMJ height with a lack of effects on the 10m sprint time after B-CA. That’s in line with a study by Dello Iacono et al., [Probably none of the previous studies examined the effect of pure unilateral CA on bilateral movement, including measuring the symmetry between the limbs. If the weaker limb performs the CA, the potential local effect of the PAPE suggested in earlier studies [Several limitations should be taken into account when interpreting the results of this study. First, the protocol of this study did not include a purely unilateral post-CA exercise; therefore, given the similarity of the movement pattern, maybe the applied unilateral DJ would be effective if the post-CA exercise were also purely unilateral. In addition, the CA volume used was the same, even though unilateral CA intensity was significantly greater compared to B-CA, so it is uncertain whether unilateral CA performed at a lower volume would also be ineffective in improving following performance. Moreover, the measurement of stiffness was limited to the measurement of the vastus lateralis only, so it is not known how the other muscle groups, which play a key role in vertical jumping and sprinting, responded. Future studies should consider the use of single-leg DJs of varying volumes, especially a lower number of sets than in this study, and their effect on a purely unilateral post-CA task.