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    Blocking movements in throwing events
    #1
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    Hi,

    I have no track and field experience but I am a retired medical/surgical doctor interested in bio-mechanics.

    In some events I believe "blocking" or "halting" movements are part of proper technique.

    I can understand that a javelin thrower will firmly put down his/her left foot just before the throw. I assume that will create a forward rotation of the body, giving a "firm push" for the throw.

    But I also believe this "blocking" is present in other events. When I read about discus throwing, I see that the thrower should forcefully push his left elbow backwards just before the release of the discus.

    In discus throwing this seems counter-productive to me. Pushing back the left elbow will decrease the rotation speed that has been build up. It would therefore make the throw shorter and less efficient.

    My question is about this blocking movement. Why does the discus thrower perform this movement? Is blocking used in other events too?

    I am completely new here, so please give any directions necessary. Have I chosen the right forum for this question?

    Thank you.
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    #2
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    Thinking in terms of a right handed thrower. A thrower wants to, for the majority of a throw, keep the left non throwing side arm (the blocking side) long and away from the torso to slow down rotation of the upper body. This helps to create greater separation/torque between the lower body/hips and the torso. At the exact moment of the "delivery" of the implement that is the point to accelerate the upper body and by shortening that left arm aggressively you then speed up the rotation while right after stopping/blocking that left side creating the hinged moment. When you accelerate the left side it also accelerates the right side. With a good block as soon as you have increased the speed of the rotation you try to immediately after that stop it. Increase the speed of rotation by shortening the left arm then suddenly stop the left side from further rotation though eventually the torso is forced to keep turning after delivery. If there is no attempt at all to stop the left side then no block will occur. The majority of the active work in a throw again for a right handed thrower is done by the right side. On the left side the leg is mostly straight or a lot of force will dissipate into the block side and not go into the throwing side. Figure skaters speed up when they bring their arms in close.

    Blocking occurs in jumps too-HJ for one. I believe in PV the vault is also a blocking action.

    Hinged moment: think about a door without a hinge. You push one side very hard and while it might move more than the other side it's probably just going to fall over. Put the door on a hinge, push it very hard on the same side and you can slam the door easily as the other side is fixed, immobilized.
    Last edited by cladthin; 08-15-2016 at 07:36 AM.
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    #3
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    Quote Originally Posted by cladthin View Post
    Thinking in terms of a right handed thrower. A thrower wants to, for the majority of a throw, keep the left non throwing side arm (the blocking side) long and away from the torso to slow down rotation of the upper body. This helps to create greater separation/torque between the lower body/hips and the torso. At the exact moment of the "delivery" of the implement that is the point to accelerate the upper body and by shortening that left arm aggressively you then speed up the rotation while right after stopping/blocking that left side creating the hinged moment. When you accelerate the left side it also accelerates the right side. With a good block as soon as you have increased the speed of the rotation you try to immediately after that stop it. Increase the speed of rotation by shortening the left arm then suddenly stop the left side from further rotation though eventually the torso is forced to keep turning after delivery. If there is no attempt at all to stop the left side then no block will occur. The majority of the active work in a throw again for a right handed thrower is done by the right side. On the left side the leg is mostly straight or a lot of force will dissipate into the block side and not go into the throwing side. Figure skaters speed up when they bring their arms in close.

    Blocking occurs in jumps too-HJ for one. I believe in PV the vault is also a blocking action.

    Hinged moment: think about a door without a hinge. You push one side very hard and while it might move more than the other side it's probably just going to fall over. Put the door on a hinge, push it very hard on the same side and you can slam the door easily as the other side is fixed, immobilized.
    Thank you for your reply and the analogy with the figure skater. That part I can understand. A figure skater making a pirouette/spin will rotate faster if the arms are moved inwards. (To maintain rotational inertia the angular velocity must increase, the work of pulling in the arms will also add energy to the movement.)

    But is there more to this movement of the left arm than just pulling it in. Since I do not have experience of this event I may have understood wrongly. But there also seems to be a movement of the left arm backwards?

    (I also assume that a high jumper will plant his foot firmly in front of him/her, in order to convert horizontal speed to vertical speed.)
    Last edited by ycc; 08-15-2016 at 08:32 AM.
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    #4
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    Quote Originally Posted by ycc View Post
    Thank you for your reply and the analogy with the figure skater. That part I can understand. A figure skater making a pirouette/spin will rotate faster if the arms are moved inwards. (To maintain rotational inertia the angular velocity must increase, the work of pulling in the arms will also add energy to the movement.)

    But is there more to this movement of the left arm than just pulling it in. Since I do not have experience of this event I may have understood wrongly. But there also seems to be a movement of the left arm backwards?
    I've coached throws going back a number of years though I'm not an every day throws coach so that might a question for someone else.

    It's a matter of pulling it in aggressively to speed up (due to the shortening of the lever-long levers are slow levers) then stop the left side which helps to speed up the right side. It is a movement backwards but also in close to the torso. For a very brief moment the thrower attempts to square their shoulders up in the direction of the throw-ideally towards the center of the sector but can only hold this for a very short time. The arm does move backwards but beyond the action of blocking the body is still rotating counter clock wise (still with the right handed thrower example) so the body keeps turning and with it the left arm. If you go on youtube, too, you will see the blocking arm is used differently depending upon which throw it is-shot, discus or javelin because of the weight differences and variation in delivery positions of each throw. There is also a block in the hammer and weight throw yet it does not involve an arm in the way the others are used-more about just firming, straightening up the left side.
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    Quote Originally Posted by cladthin View Post
    I've coached throws going back a number of years though I'm not an every day throws coach so that might a question for someone else.

    It's a matter of pulling it in aggressively to speed up (due to the shortening of the lever-long levers are slow levers) then stop the left side which helps to speed up the right side. It is a movement backwards but also in close to the torso. For a very brief moment the thrower attempts to square their shoulders up in the direction of the throw-ideally towards the center of the sector but can only hold this for a very short time. The arm does move backwards but beyond the action of blocking the body is still rotating counter clock wise (still with the right handed thrower example) so the body keeps turning and with it the left arm. If you go on youtube, too, you will see the blocking arm is used differently depending upon which throw it is-shot, discus or javelin because of the weight differences and variation in delivery positions of each throw. There is also a block in the hammer and weight throw yet it does not involve an arm in the way the others are used-more about just firming, straightening up the left side.
    Here is a youtube
    https://www.youtube.com/watch?v=flQnM4rCnjw
    blocking is discussed, starting at 4'30"

    Maybe the pulling back of the left elbow in discus is more related to how the body functions and less to physics (which I first thought)? As I understand this coach, moving the left arm backwards will stretch the muscles on the front side of the thorax and give the muscles on the right side a stronger "anchoring" for powering release. (I would guess the pectoralis major is heavily involved, among other muscles.) Getting the left side out of the way may be needed to give room for the release?

    The reason I ask is that I like to compare with golf, which I know more about. One classical tip in golf is "hit (the arms/shoulders) against a firm left side", do not "spin out" the hips completely. But on the other hand, I think I sometimes see strong power hitters in golf rotate the hips and shoulders very forcefully through impact when they go for maximum distance.
    Last edited by ycc; 08-15-2016 at 09:10 AM.
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