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Old 03-04-2013, 12:14 PM   #139
julian
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Default Is it only elastic energy?

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Originally Posted by WildVolley View Post
Interesting post. Yandell discusses two things, the extent of the arm bend and which hand is more dominant. He says
1) the Williams sisters hit more bent arm and more open stance, like an off-arm forehand &
2) many of the men hit straighter arm and more closed stance and with more bottom hand dominance.

I just went and played with some shadow swings and find that I can swing from an open stance with a straight left arm (I'm right handed). So I'll need to go on a court and see what problems this creates. Because you have to reach over with the bottom hand, the shoulders can't be as open as on a single handed forehand, but I still seem to be able to generate plenty of racket head speed.

I think it may have more to do with the takeback and balance, but that's just a hypothesis.
Combined effect of elastic energy and myoelectrical potentiation during stretch-shortening cycle exercise

C. BOSCO,
J. T. VIITASALO,
P. V. KOMI,
P. LUHTANEN

Article first published online: 8 DEC 2008

DOI: 10.1111/j.1748-1716.1982.tb07024.x

1982 Scandinavian Physiological Society

Issue
Acta Physiologica Scandinavica
Acta Physiologica Scandinavica

Volume 114, Issue 4, pages 557565, April 1982

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Keywords:

Muscle mechanics;
stretch-shortening cycle;
muscle elasticity;
muscle activation;
myoelectrical potentiation

In addition to the utilization of muscle's elastic energy enhancement of performance in exercise involving stretch-shortening cycle might be also due to simultaneous increase of myoelectrical activity. This hypothesis was tested by examining three athletes during jumping exercise on force-platform. Vertical jumps were performed with and without preliminary counter-movement, and the jumps were called counter-movement jump (CMJ) and squatting jump (SJ), respectively. In both conditions several jumps were performed also with extra loads on the shoulders (15220% of b. wt.). Additional droppingjumps (DJ) were executed from different heights (20100 cm). During jumping exercise myoelectrical activity of selected muscles from the quadriceps femoris was monitored with surface electrodes. The results obtained were similar to those reported in isolated muscle and as expected, the prestretch in CMJ shifted the force-velocity curve of concentric work to the right. In two cases enhancement of performance was attributed primarily to restitution of elastic energy because myoelectrical activity was similar to that observed in SJ. In one subject increased myoelectrical activity was observed during the concentric phase of CMJ. In DJ condition the EMG activity during eccentric phase was much higher than in SJ. Therefore the high performance in this condition was attributed to both elastic energy and reflex potentiation. In eccentric work of CMJ the average force decreased with the increase of stretching speed. This phenomenon was associated with a light increase of EMG activity. The observed results emphasize that both elastic energy and reflex potentiation may operate effectively during stretch-shortening cycle activity.
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