96% in the RFS with respect to RTS ( p < 0.05 ). Similarly, the linear momentum��s vertical component of the upper limbs (py ul ) was increased by 25.69% ( p < 0.05 ) in favour of the RFS. Also, the horizontal component (px ul ) was increased by 31.01% in the RTS with respect to RFS ( p < 0.05 ) and the linear momentum��s vertical Sorafenib Tosylate chemical structure component of the trunk (py tc ) was significantly increased by 88.29% in the same condition ( p < 0.05 ) ( Table 2 ). Interestingly, the linear momentum��s vertical component of the lower limbs (py ll ) and the linear momentum��s horizontal component of the trunk (px tc ) did not differ between both conditions. With regards to the kinematic data, the take-off angle (�� t ) was decreased in the RFS series with respect to RTS: (�� = �C 12.07% with p < 0.05 ).
Moreover, the shoulder joint��s angle at the take-off (�� s ) was increased by 35.48% ( p < 0.05 ) and the hip joint��s angular displacement (�� h ) was increased by 30.23% ( p < 0.05 ). The hip joint��s angle at the take-off (�� h ) was increased in RTS series with respect to RFS: (�� = 19.88% with p < 0.05 ). Likewise, the angular velocity of the hip joint (�� h ): (�� = 21.93% with p < 0.05 ) and the horizontal displacement of the COM (dx): (�� = 8.39% with p < 0.05 ) were all increased. Moreover, the vertical displacement of the COM (dy) was decreased in RTS with respect to RFS: (�� = 37.09% with p < 0.05 ) and the same was observed for the vertical velocity (vy): (�� = 20.62% with p < 0.05 ). The angular velocity of the shoulder joint (�� s ) and the knee joint (�� k ) did not vary during the different backswings connection series.
In the same way, the knee joint��s angle (�� k ), the angular displacement at the shoulder joint (�� s ) and the knee joint (�� k ) remained almost identical during the take-off. Finally, the horizontal velocity of the COM (vx) was approximately equal ( Table 1 ). Discussion Two crucial biomechanical criteria are considered when assessing the technical performance of backswing connection in back acrobatic series: vertical velocity at the take-off and vertical elevation of the gymnast��s centre of mass during the aerial phase of the somersault. With a better velocity and elevation of the COM, the stability of landing is much more secured, particularly when combined with longitudinal rotations (twists).
This study is focused on the variables that could affect take-off phases by comparing them between two different acrobatic series. The different backswing connection did not affect the direct kinetic data at the take-off during the stretched back somersault. The vertical force and the maximal rate of force development remained almost identical. Moreover, the indirect Entinostat kinetic data showed a significant difference ( p < 0.05 ). The RTS connection allowed a larger linear momentum of the trunk on the vertical axis and the upper limbs on the horizontal axis ( Figure 2a and 2b ).