Effectiveness of the Involvement Of Selected Muscles During the Pre-Jump and Wind-Up Phase During the Execution of a Spike In U16 – U18 Female Beach Volleyball Players

Background: „Laterality in beach volleyball is mainly manifested in the attacking activities of an individual (serving, spiking). Functional asymmetry affects the player’s movement expression in all movement situations, and laterality is also important for the specialization of individual players.Objective: The study aims to assess the lateral involvement of selected muscles (deltoideus, biceps femoris semitendinosus) and their efficiency in the phases before the spike jump and in the wind-up phase of the spike.Materials and Methods: The research group consisted of 12 female players with an average age 16.17 (SD= 1.5). The main method used for data collection was measurement by Noraxon surface electromyography. We entered the transformed data into Microsoft Excel 365 for Mac. To evaluate the data, we used descriptive (frequency, percentage) and inferential (Shapiro-Wilk test, T-test, Man Whitney U test and correlation) statistical methods. Results: The conclusion of the study is that there is no difference between the right and left sides in the evaluated muscle groups (deltoideus= 0.206; biceps femoris=0.569; semitendinosus=0.792). An interesting finding of the study is the strong correlation between the left deltoideus and the right biceps is interesting (0.812). The efficiency is higher in the wind-up phase of all the assessed muscles. The highest difference in efficiency is in the biceps femoris on the left leg, where the difference in efficiency of engagement in individual phases is over 25%. Conversely, the lowest difference is for the left semitendinosus (5.5%).Conclusions: The study confirms that the effectiveness of muscle activity is more efficient in the wind-up phase, at the same time we add that in this phase the muscles work more symmetrically.