Observing Propulsion

Observing Propulsion

Post by Donal Fag » Thu, 14 Sep 2000 04:00:00


Quote:

>At the time his "Swimming Even Faster" book was written,
>Maglischo (and many other coaches) were still
>believers/advocates  in the "lift" theory of propulsion,
>popularized by "Doc" Counsilman.

Actually, Maglischo discusses five theories of propulsion:
Propulsive Drag - Push-Straight-Back-To-Go-Forward (Counsilman)
Propulsive Drag - Weaving Back Theory (Counsilman)
Lift - Bernoulli's Theorem (Counsilman)
Vortex - Foil Propulsion (Colwin)
Vortex - Fling-Ring (Colwin)
and grants that several are worthy of consideration, but closes
with a cautious acceptance of Propulsive Lift, in which Newtonian
reactions to diagonal sculling strokes, rather than Bernoulli
forces, play the primary role.  This is a partial repudiation of
Counsilman's Lift Theory.

Quote:
>Today, however, there are few believers in the lift theory, ...
>So Maglischo's point about "two phase insweep/outsweep" swimmers
>is no longer an adequate description of the separation between
>what I have termed kayakers and hitchers.

I'd be interested in hearing what propulsion theories people *do*
believe.  But, whether or not one agrees with Maglischo's
conclusions, I don't think one can dismiss his observations so
easily.  He is clearly trying to resolve various theories with
these observations, not tailoring his observations to fit a pet
theory.

I trust Larry's observations as far as recovery, reach and maybe
even the catch, but I just don't believe he can see enough of
what happens beneath a swimmer from poolside, not to mention from
the grandstand, to speak with real certainty about propulsion.  
Perhaps he can find a more recent "controlled study" in which
there are clear observations of propulsive motion that
complement his above-pool observations.

 
 
 

Observing Propulsion

Post by Isiaf » Fri, 15 Sep 2000 09:23:37

Quote:
>I'd be interested in hearing what propulsion theories people *do*
>believe.

Well, just to add some real world experience.  It might be worthy to note that
in flat water sprint kayaking a winded or cupped paddle is uses and the stroke
is outward from the board rather than backward.

Of course, a propeller boat works better than a paddle wheel board apparently
based up boat design over the years.

On my longboard surfboard, I find that an outward scull action like the kayak
stroke mentioned above, feels much faster for paddling out.

Sling Skate

 
 
 

Observing Propulsion

Post by STP » Fri, 15 Sep 2000 04:00:00


Quote:

> I'd be interested in hearing what propulsion theories people *do*
> believe.  But, whether or not one agrees with Maglischo's
> conclusions, I don't think one can dismiss his observations so
> easily.  He is clearly trying to resolve various theories with
> these observations, not tailoring his observations to fit a pet
> theory.

What's this?  Someone is actually interested in what makes a swimmer move?
I thought there was a prohibition on raising such basic issues on this
board. ;)

I have to go with one of the "propulsive drag" theories.  The hand connects
to the water and is used as an anchor to apply force to propel the swimmer
forward.  [While "lift" can be a source of propulsion in a fluid (I assume
this means the effect caused by differing pressures like in an air foil or
propellor) my gut reaction is that a human can not genrate enough force to
produce this effect in any meaningful quantity.  I don't know what a
"vortex" is but it sounds too scary to be useful. ]

Actually, when you look at it this way, swimming is pretty easy to
understand for all but the most serious competetors.  I'll have to say that
after a month or so of reading this board, I think you guys are making this
WAY too complicated but I understand that you all love the sport and are
just having fun debating.

Quote:
> I trust Larry's observations as far as recovery, reach and maybe
> even the catch, but I just don't believe he can see enough of
> what happens beneath a swimmer from poolside, not to mention from
> the grandstand, to speak with real certainty about propulsion.
> Perhaps he can find a more recent "controlled study" in which
> there are clear observations of propulsive motion that
> complement his above-pool observations.

I agree but I do not mean to agree to any implied criticism of Larry because
he seems to be up front about the limits of his observations.  Even if you
can accurately observe the stroke mechanics of swimmers from the deck (which
is very difficult if not impossible), 2 swimmers may go through exactly the
same range of motion but be generating different force levels at different
points along the stroke.  IMHO, merely observing the path of the hand and
arm (and feet) through the water can not tell the whole story about what is
actually propelling a particular swimmer through the water.

STP

 
 
 

Observing Propulsion

Post by RunnSw » Fri, 15 Sep 2000 04:00:00

Let me more clearly explain my observations concerning insweeps.

I've been very interested in this for many years, because, when I resumed
regular swimming in 1981, I thought it would be good to get some professional
swimming lessons, because I thought a lot had changed since the mid-60s, when I
quit the sport (I've since attended many stroke clinics and received lessons
from various teachers, both for myself and for other family members).

Anyway, the first teacher explained Counsilman's Bernoulli's lift theories and
said that most coaches were (at the time) teaching S curves, but he thought
that a very sharp, fast insweep to a point past the midline was optimum,
followed by an outsweep and strong push back to finish the stroke.  So I swam
this way for many years, until reading (somewhere along the way) that straight
back "drag propulsion" swimming was better.

So what I have always looked for is the inward versus backward movement of the
leading hand.  I think that one doesn't need underwater views to gauge
this...just stand at the end of the lane and watch the incoming swimmers to see
if there is a distinct inward movement to the leading hand or if there is no
distinct inward movement.

What I've observed in non-elite age group and *** swimmers is that many of
them do have a pronounced insweep, often crossing the the midline by a large
amount.  This tends to be more pronounced on the non-breathing side and is
often accompanied by a dropped elbow (harder to judge above water, but, with
lots of experience, I think I've gotten pretty good at it).

But, at the elite level, I don't remember seeing anyone who comes anywhere near
crossing the midline.  It's anchor and the hand doesn't really move much inward
at all.  I think that the elite swimmers are pretty much all "drag" swimmers,
who don't do prominent diagonal insweeps as described by Maglischo.

The above should be pretty easy to confirm or refute.

I read somewhere else that the velocity required to achieve a true "lift"
cannot be obtained by a swimmer.  Perhaps kayaking is different.  But is the
kayak paddle curved to provide "lift," or just to avoid spilling water?  I'm
asking a question; I don't know anything about kayaking at all - unlike what I
do know about gymnastic injuries :)

- Larry Weisenthal

 
 
 

Observing Propulsion

Post by STP » Fri, 15 Sep 2000 04:00:00


Quote:

> What I've observed in non-elite age group and *** swimmers is that many
of
> them do have a pronounced insweep, often crossing the the midline by a
large
> amount.  This tends to be more pronounced on the non-breathing side and is
> often accompanied by a dropped elbow (harder to judge above water, but,
with
> lots of experience, I think I've gotten pretty good at it).

> But, at the elite level, I don't remember seeing anyone who comes anywhere
near
> crossing the midline.  It's anchor and the hand doesn't really move much
inward
> at all.  I think that the elite swimmers are pretty much all "drag"
swimmers,
> who don't do prominent diagonal insweeps as described by Maglischo.

Here's a theory (or two) on insweeps/outsweeps or "sculling."  First, I do
not think the movement directly produce forward propulsion but relates to
creating biomechanical advantage by certain individual swimmers.  As the
stroke progresses, the hand is moved outward or inward to a position where,
at that point in the stroke, more force can be generated by the swimmer.
Some swimmers need to do this some don't.  Conversely, in weaker swimmers, a
"sculling" motion may result from the swimmer intentionally getting out of a
position where he/she can not apply sufficient force to maintain speed.  (It
's one thing to learn proper technique, its another to be strong enough to
use it).  I believe this is why you see this action much more often in
weaker swimmers.  They are "bailing out" of the stroke to some degree
because the do not have the ability to complete a "perfect" stroke.  (I
vividly remember as a kid being told to "improve" my stroke and
understanding exactly what my coach wanted me to do but being too weak to
keep my arm/hand in a "proper" position all the way through the stroke.  As
I got stronger, I could improve my stroke and I went faster).

Second, I've heard the theory advanced that as the stroke progresses, a
column of water can be put in motion by the force of the hand which results
in a loss of efficiency and that an advantage is gained by "searching" for
and finding still water, hence a "sculling" motion in the stroke.
Personally, I've never noticed this effect while swimming but when paddling
a canoe hard, it seems to really happen.

STP

 
 
 

Observing Propulsion

Post by STP » Fri, 15 Sep 2000 04:00:00


Quote:

> What I've observed in non-elite age group and *** swimmers is that many
of
> them do have a pronounced insweep, often crossing the the midline by a
large
> amount.  This tends to be more pronounced on the non-breathing side and is
> often accompanied by a dropped elbow (harder to judge above water, but,
with
> lots of experience, I think I've gotten pretty good at it).

> But, at the elite level, I don't remember seeing anyone who comes anywhere
near
> crossing the midline.  It's anchor and the hand doesn't really move much
inward
> at all.  I think that the elite swimmers are pretty much all "drag"
swimmers,
> who don't do prominent diagonal insweeps as described by Maglischo.

Do you think that one factor in this difference might be related to a
relative lack of shoulder flexibility in the ***/ non elite swimmers?  As
I try to picture this while sitting at my desk, I think that as the body
rolls the arm must flex more at the shoulder for the hand to maintain the
same relative position to the midline of the body.

STP