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Isometric torque of arm abduction and adduction muscles in men

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Dulawski G., Bober T., Czamara A., Zaleski A.

2008

vol. 16

issue 2

13-18

Przedmiotem pracy były pomiary statycznych momentów sił grup mięśni odwodzących i przywodzących ramię (w płasz-czyźnie czołowej). Badania wykonano na urządzeniu Biodex Medical System Pro 3 u 15 mężczyzn praworęcznych. Pomiary maksymalnych momentów sił w 5 wybranych pozycjach kątowych pomiędzy 0° (ramię wzdłuż tułowia) a 120° (dla obu kierunków) pozwoliły przebiegi moment-kąt opisać wielomianami drugiego stopnia. Przebieg momentu siły mięśni odwodzących ramię w funkcji kąta ma kształt hiperboli z maksimum przy kącie 0°, a dla mięśni przywodzących przyjmuje kształt paraboli z maksimum przy kącie 45°. Grupa mięśni odwodzących wyzwala większy moment siły od przywodzacych przy kącie 0° i 120°. W pozostałych, pośrednich, pozycjach kątowych jest niewielka przewaga mięśni przywodzą-cych nad odwodzącymi.

The aim of work was to present the results of maximal (isometric) torque produced by muscles acting as arm abductors and adductors (frontal plane). The Biodex Medical System was applied to test the group of 15, right handed, young men. Torque was measured at 5 different angular positions between 0° (arm along the trunk) and 120° in both directions. The torque-angle curves were approximated with polynomial of the second order. The abduction torque-angle curve has a shape of hyperbola with maximum at 0° and adduction torque has a form of parabola with maximum at 45°. Abduction muscle group is stronger than adduction muscle group in the position of 0° and 120°. In the remaining positions the adduction muscle group is stronger than abduction muscle group.

The Kinematics of Trunk and Upper Extremities in One-Handed and Two-Handed Backhand Stroke

100%

Stępień A., Bober T., Zawadzki J.

Journal of Human Kinetics

2011

vol. 30

37-47

The aim of this study was to present kinematics of trunk and upper extremities in tennis players who perform one-handed and two-handed backhand strokes. The study aimed to address the question of whether one of those techniques has some important advantage over the other. If so, what makes it superior?The study included 10 tennis coaches with average coaching experience of 9 years. The coaches were asked to hit 15 one-handed and two-handed backhands. The tests were carried out in a laboratory. A sponge ball was used in order to protect the measurement equipment. Video motion analysis was carried out using BTS SMART system; images were recorded with 6 cameras with a rate of 120 frames per second. The analysis of both backhand strokes focused on the second phase of the stroke (acceleration).The use of an eight-element model of human body for description of upper body motion in both techniques revealed kinematic differences in how both backhands are performed. The two-handed backhand was performed in closed kinetic chain with 8 degrees of freedom, whereas the one-handed backhand involved an open kinetic chain with 7 degrees of freedom. Higher rigidity of upper extremities which are connected with trunk in the two-handed backhand, contributes to an elevated trunk effect in this stroke. This is confirmed by higher component velocities for racket handle, which result from trunk rotation in the two-handed backhand and a negative separation angle in the two-handed backhand at the moment of contact of the racket with the ball.The study does not provide a clear-cut answer to the question of advantages of one technique over the other; however, it reveals dissimilar patterns of driving the racket in both techniques, which suggests the need for extending the analysis of techniques of both backhands with additional kinematics of tennis racket in consideration of measurements of ball velocities.

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Isometric torque of arm abduction and adduction muscles in men

The Kinematics of Trunk and Upper Extremities in One-Handed and Two-Handed Backhand Stroke