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  #61  
Old 07-18-2012
CoachSuzanne CoachSuzanne is offline
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Quote:
Originally Posted by swimust View Post
:) :) :) thanks very much! i just laughed out loud.
seriously, i swear i dont have any intention to play mind games. its all really happening to me. No frontal coach, no sanity...
;) Thank you...you appreciated it in the right light.
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  #62  
Old 07-18-2012
CoachSuzanne CoachSuzanne is offline
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Just want to throw out there that the differences in density between air & water are what allow friction of the stroking arm to move us forward rather than braking us, and that allow the momentum of the recoverying arm to result in the same force applied rearwards against a denser medium via the anchoring arm. So yes, while their is slippage, if one things that to move forward you must slip some...you'll have an entirely different stroke and muscle movement pattern than if one things that to move forward you anchor and spear past.

In the end it comes to re-education of the relationship of muscle groups and movement firing patterns with one another. Everyone has the "strength" to swim well. Swimming faster requires the ability to selectively apply pressure force and (yes) acceleration of the stroking arm without inhibiting the relationships that make the swim posture efficient.
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Suzanne Atkinson, MD
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USA Paralympic Triathlon Coach
Coach of 5 time USA Triathlon Triathlete of the Year, Kirsten Sass
Steel City Endurance, LTD
Fresh Freestyle

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  #63  
Old 07-18-2012
swimust swimust is offline
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Originally Posted by CoachSuzanne View Post
Swimming faster requires the ability to selectively apply pressure force and (yes) acceleration of the stroking arm without inhibiting the relationships that make the swim posture efficient.
Or in a much more scientific language: "feel the water". Please raise the level of your explanations. Next time please try and use a bit of professional vocabulary ;)

btw, I am using the forum spell checker now. I deserve a medal for that, and god help me if you gone really use your professional jargon.
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Last edited by swimust : 07-18-2012 at 10:55 AM.
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  #64  
Old 02-25-2013
yurenhui yurenhui is offline
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In my opinion,the acceleration means the acceleration of the body roll which will result in the acceleration of the pulling arm.And the acceleration force of the body roll comes from the kick of the leg which is in the same side of the pulling arm.
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  #65  
Old 04-20-2013
hydrophobe hydrophobe is offline
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Default terminology questioned

Hello all. I’m a beginner swimmer, having only started to learn front crawl near the end of last year. I’ve read the TI FS book and watched the video and, taken with regular (non TI specific) coaching, I’m improving steadily. I’m impressed by the TI approach, which seems perfectly geared towards those who will not become Olympians, but who want to enjoy swimming on a continuously improving basis and who take responsibility for their own development.

I like that the founder appears to be a true gentleman and that neither he nor those involved in TI try to claim that the system is the Holy Grail of swimming. I also like the open-minded climate on this forum.

I’m working to improve my understanding of the mechanics of swimming and I know I have a lot of work to do. I hesitate to step into a debate where seasoned practitioners and coaches are in disagreement, but if there is one area which seems a little patchy, it is the use of scientific terminology.
My first degree is in Engineering, with a focus on dynamics and fluid mechanics. Most of my career to date has been in a separate field of technology however, so I may be a bit ropey. Nevertheless, I hope the following will be helpful.

1. I don’t believe that ‘acceleration’ is a meaningful property in the context of this thread. Acceleration defines an increase in speed. If a stationary body, floating in water, receives a single push, it accelerates to a maximum speed, and then decelerates back to rest. If a single push moves the body a distance of 3m in water, approximately 1.5m will have been travelled whilst accelerating and 1.5m will have been travelled whilst decelerating. We wouldn’t discount the second half of the distance travelled, just because the body was decelerating.

More useful, is the property that moves a body forward i.e. the resistive force applied by the water in the direction of motion: ‘propulsion’, ‘thrust’ or ‘drive’.

2. The term ‘momentum’ also seems to be misused. Someone already mentioned in this thread that throwing an arm forward in itself cannot possibly result in forward motion. If it does so, then it must be acting in concert with another body movement, e.g. where Terry talks of having “everything firing at once”, from toe flick to rotation to spearing opposite-side fingertips. It’s the combination that counts.

Momentum is mass multiplied by velocity and its conservation is a fundamental principle of modern science. A motionless body has zero momentum. Even if it finds a way of moving part of itself, there will be an equal and opposite reaction on the rest of the body.

As a starting model (simplified)….imagine you are lying motionless in the water with your arm by your side and you violently throw your arm forward (without kicking or making any other movement). If your arm weighs 10kg and you manage to hurl it at 50m/sec (again, a simplified model), then its momentum is 500kg.m/s. By the act of throwing the arm, you must also create the same momentum in the opposite direction, so if the rest of your body weighed 100kg, your body would be inclined to move backwards at 5m/sec. Of course, since your arm is connected to your body, you remain fixed on the spot.

Suzanne mentioned that the key is in the difference in fluid densities… water is denser and requires more effort to displace than the air through which the arm is travelling. Whilst that is true, the force delivered by the floating body, that throws the arm through the air, can only exist if an equal and opposite force is placed on the rest of the body, so again, no axial movement should occur.

Please forgive a rookie swimmer for butting in. My intentions are good and I’m perfectly happy to be challenged on any of this :)

Last edited by hydrophobe : 04-20-2013 at 05:39 PM.
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  #66  
Old 04-20-2013
borate borate is offline
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Quote:
Originally Posted by hydrophobe View Post
I’m working to improve my understanding of the mechanics of swimming and I know I have a lot of work to do <snip> but if there is one area which seems a little patchy, it is the use of scientific terminology.
My first degree is in Engineering, with a focus on dynamics and fluid mechanics.
Considering your background, you may enjoy this (somewhat dated) dissertation.
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  #67  
Old 04-21-2013
hydrophobe hydrophobe is offline
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Many thanks for this post. When you say that it's dated, other than having been written in 2004, what has changed in popular thinking? The paper refers to 'catch-up stroke' used in order to keep more body mass forward of the centre of buoyancy. Would we be more inclined to use the term 'front-quadrant swimming' now?
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  #68  
Old 04-21-2013
CharlesCouturier CharlesCouturier is offline
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Quote:
Originally Posted by hydrophobe View Post
1. I don’t believe that ‘acceleration’ is a meaningful property in the context of this thread.
Acceleration in the context of this thread refers to hand velocity dynamics, not to the body forward velocity.

In this context, not only is it a meaningful property, I'd say that it's one of the most important properties when come to swimming fast.

You get to discover the importance of this property only when starting a quest for gaining more speed.

Last edited by CharlesCouturier : 04-21-2013 at 05:57 PM.
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  #69  
Old 04-21-2013
hydrophobe hydrophobe is offline
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Quote:
Originally Posted by CharlesCouturier View Post
Acceleration in the context of this thread refers to hand velocity dynamics, not to the body forward velocity..

Are you thinking of the 'push' phase of the stroke? If you say that it's important that the hand accelerates during this phase, I guess most would agree...?

Alternatively, if we use the 'anchor' metaphor, then maybe we would say that during the conventionally named 'push' phase, then, because of the increasing force applied to the relatively static hand, the body accelerates past it? :)
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  #70  
Old 04-23-2013
swimust swimust is offline
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I just want to "come clean" about this thread that I started long ago. 9 months ago.

Since posting this thread I changed and tried zillion things in my swim. I actually do not take any responsibility on my posts here!! :)
my apologies.

p.s. - the thread title sounds correct though. Don't use "shoulder drive" to get propulsion.
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Last edited by swimust : 04-23-2013 at 03:42 PM.
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