Abstract
Our aim was to conduct a kinematic and electromyographic characterization of the water polo front crawl while leading the ball technique. A high level male water polo player performed an experimental protocol of 3x15m at front crawl while leading the ball (with rest intervals of 2min between repetitions). Each repetition was performed in acceleration. One complete stroke cycle was analyzed for each repetition of 15m using surface electromyography to analyse the biceps femoris, gastrocnemius medialis, tricips brachii, b좥ps brachii, deltoideus posterior and rectus femoris muscles. The protocol was also recorded by 2 surface and 4 underwater cameras in order to assess centre of mass (CM) velocity during the cycle and its fluctuations. EMG signal was digital filtered (35-500Hz), full-wave rectified, calculated the linear envelope, normalized to the maximal isometric voluntary contraction and integrated (iEMG). The fluctuations of CM velocity were assessed though the coefficient of variation of the instantaneous velocity. Results showed that tricips brachii and gastrocnemius medialis were the most active muscles in the beginning of the cycle and that gastrocnemius medialis, deltoideus posterior and tricips brachii displayed the highest values (and b좥ps brachii the lower values) of maximum electric activity and iEMG. It was observed an increase in the velocity of the CM at the beginning of the cycle, decreasing slightly afterwards, implying a reduced coefficient of variation (16.8). It should be evidenced the different involvement of the studied muscles in the cycle of front crawl while leading the ball and the consequent differences in the CM velocity.
Highlights
One of the most important skills in water polo is the front crawl technique, which, from all the swimming volume that is done during a match, occupies 89.5%, being a distance of 280 to 430m performed at maximum or sub-maximum intensity [1]
The water polo player does not move at a constant velocity, existing accelerations and decelerations of the centre of mass (CM), even in a single stroke cycle [2], which are the effect of non-constant resistive and propulsive forces acting upon the athlete’s body
It is visible that gastrocnemius medialis (GM), deltoideus posterior (DP) and tricips brachii (TB) display the highest values of maximum electric activity (TB presents smaller variation’s coefficient relatively to the DP evidencing lower variability in the analyzed cycles)
Summary
One of the most important skills in water polo is the front crawl technique, which, from all the swimming volume that is done during a match, occupies 89.5%, being a distance of 280 to 430m (about 27.9%) performed at maximum or sub-maximum intensity [1]. The water polo player does not move at a constant velocity, existing accelerations and decelerations of the centre of mass (CM), even in a single stroke cycle [2], which are the effect of non-constant resistive and propulsive forces acting upon the athlete’s body. These velocity variations within a stroke cycle are known as intracyclic speed fluctuations (dv) [3], being considered as an indicator of the inverse of swimming efficiency [4]
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