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Abstract Details

Abstract Title

Electromyographic activity of Upper Trapezius and Serratus Anterior Muscles in Volleyball Players during the Block

Abstract Theme

Sport nutrition

Type Presentation

Poster

Abstract Authors

Presenter Yanne de Toledo Pinho - Federal University of São Paulo (Human Kinetics Laboratory) - BR
Ricardo Luis Fernandes Guerra - Federal University of São Paulo (Human Moviment Sciences Department) - BR
Helga Tatiana Tucci - Federal University of São Paulo (Department of Human Moviment Science) - BR

Presentation Details

Poster Exhibition Site (Local): Purple - 8        Date: 1 September        Time: 8am to 7pm        Presenter: Yanne Pinho

Abstract Resume

Background: Understanding shoulder muscle activity during fundamentals of volleyball may help to define shoulder protocols for training and rehabilitation, reducing the risk of injury
and increasing sports performance. The objective of the study was to analyze the surface electromyographic activity (SEMG) of upper trapezius (UT) and serratus anterior (SA) muscles in volleyball
players during the block. Block is the technical action that has the greater propensity to cause shoulder injury due to the large impact of upper extremity with the ball. Methods:
Five healthy, right-handed males were recruited. The study had two stages: (1) physical evaluation; (2) UT and SA SEMG data collection during the execution of block. Each athlete performed up to 5
attempts of block, with an interval of 30 seconds. Attempt was considered appropriate when the ball just touched the right hand. Only the corrected first 3 attempts were considered for analysis. The
Block phases "arm elevation"; "touch on the ball" and "arm lowering" were delimited by a trigger for further windowing of the SEMG in each phase. Also, SEMG of muscles were sampled during three
maximal voluntary isometric contractions (CIVMs) collected in the position of muscle function. Signal was sampled with a 16-bit A/D converter board, frequency of 2 kHz per channel and simultaneous
acquisition. Myoelectric signal were sampled by a disposable Ag/AgCl bipolar electrode (20mm inter-electrode distance) connected to a sensor with automatic gain (Miotec©, RS, Brazil). A channel was
used as a trigger. A circular disposable electrode was fixed in the sternum for reducing acquisition noise. SEMG signal were filtered at a frequency bandwidth of 20-500Hz and after windowed in each
phase. Then, raw signal was normalized by the mean value of the 3 MVICs of the respective muscle. Thus, the normalized electromyographic activity was expressed in percentage values. Percentage values
of normalized SEMG were compared between phases. Normalized electromyographic variables were analyzed by the model of analysis of variance with repeated measures and then by the method of multiple
comparisons of Bonferroni. The level of significance was set at α=0.05. Results: UT showed greater active [mean=88.32 (standard deviation=28.78)] in the "touch on the ball" compared
to "arm elevation" [34.20 (11.09)] and "arm lowering" [33.23 (20.02)]. SA showed greater active in the "touch on the ball" [101.26 (44.32)] compared to "arm elevation" phase [27.92 (8.45)] and "arm
lowering" [26.63 (13.16)]. Conclusion: Results suggested that UT muscle showed greater activation when compared to SA muscle in almost all analyzed phases. However, serratus anterior
was the most recruited muscle in the "touch of the ball", phase where subjects executes the greater amount of force among all analyzed phases of block. Results should be viewed with caution, as the
sample is small for accurate conclusions.


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