Re: [Paddlewise] A new way to teach the forward stroke?

On 28/04/2011 12:12 PM, Niels Blaauw wrote:
> MATT MARINER BROZE wrote:
>
>  > Off the cuff, it seems to me that there IS potential energy stored
> by lifting
>  > the arms but I don't see any advantage to doing that since the
> paddle is
>  > nowhere near 100% efficient in transferring that energy into
> forward motion.
> I'm not so sure about that. The mechanics are complicated, but let's
> simply ask: If the energy doesn't transfer to the force and movement
> of the paddle-blade, then where does it go? The movement of the arms
> is nearly frictionless. Nothing heats up, so no energy is lost.
> I think almost 100% of the energy transfers to the paddleblade - but
> from there, I have no idea of the efficiency of a blade pushing
> against the water.

I would disagree that "nothing heats up, so no energy is lost". 
Exercise does create heat in the muscles, else there would be no need 
for profuse sweating to cool the body down during strenuous exercise.

But I suspect the amount of energy referred to is small. I doubt you 
could get a kayak to move forward by just using the potential energy 
stored by the effort of lifting the paddle up. Even on a completely 
calm day.

In fact, I suspect this line of reasoning might be accused of counting 
the number of angels to dance on the head of a pin.

My point of view is something like this: the muscles in your shoulders 
(used for lifting the paddle) are weaker than the core muscles used to 
power a forward stroke using rotation. Therefore, one should reduce 
the work done by the shoulders (and arm) muscles to as great an extent 
as possible, and rely instead on the core muscles to do the work of 
moving the boat forward.

You might gain some small advantage by lifting the paddle to a 
slightly greater extent, but I suspect this to be of relatively short 
duration and the advantage would reduce as the shoulder and arm 
muscles tired. During a longer paddle, the gain would be so small as 
to be non-existent.

But I am open to arguments proving me wrong. Lord knows, at my age, I 
can use all the advantages I can get to keep up with my younger 
paddling friends.

-- 
   Darryl


>
>  > Therefore, the more work you put into lifting the paddle the more
> energy you
>  > waste because of the lack of paddling efficiency gained in return
> for your
>  > efforts against gravity. If I'm correct about that, then other
> things being
>  > equal the less you work against gravity during your strokes the
> more efficient
>  > you should be.
> It is indeed possible that a horizontal stroke is more efficient than
> a vertical stroke. The mechanics and physiology are too difficult to
> put in a simple model. The main reason I consider the vertical stroke
> the best, is that it's been taught by most kayak-instructors and used
> by most paddlers. Once they master that stroke, they're able to keep
> it up for hours and stay with the group, so I think there must be
> something good about it.
>
>  > This is probably one of the reasons why a bent shaft canoe
>  > stroke is more efficient than a kayak paddle stroke, less energy
> wasted
>  > lifting the second paddle blade, hand, and arm against gravity and
> more of
>  > ones effort going to propelling the kayak horizontally through the
> water.
> Efficiency is one thing; being able to keep it up is another. I tried
> it for myself: I can (in my home, with a paddle out of the water)
> longer keep up a forward-stroke motion than a static position. There
> might be a placebo-effect there: I _want_ to be able to keep it up
> longer.
>
> I don't know if moving an arm uses more energy than keeping an arm
> steady against a force. To a steel crane, it certainly would be, but
> muscles work differently. They're comparable to a car-engine working
> against the clutch, with the car on the handbrake. Lots of energy are
> generated, but none is transferred to forward motion.
> There might be a trade-off somewhere: If you move half of the time and
> rest the other half, you might be more efficient than when you keep
> the arm steady, constantly bearing the weight. I don't know.
>
> Perhaps I step too lightly over what the best stroke is. I could
> change it to: "If you teach a vertical stroke, than THIS should be
> your justification".
>
> Thanks for joining the discussion, Matt. I highly value your expertise.
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