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

On 28/04/2011 4:34 PM, Niels Blaauw wrote:
> Darryl Johnson wrote:
>
>> 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.
>
> We were specifically talking about the energy that's lost while
> _relaxing_ the muscles and letting the paddle drop. While your point
> is valid for exercise, it's not for this specific case of rest.
>>
>> 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.
>
> You must have missed my calculations. In my own stroke, analyzed in my
> own video, I put close to 30 watts into lifting the paddle, while 30
> watts drive a kayak at a speed of 2 kts.
> There will be losses, but still: 30 watts is a significant amount of
> power.

I am not a physicist, and, yes, I did skim over your calculations, so 
I may have missed an important point. But from empirical observation, 
I can't believe that you gain enough energy to move a kayak simply by 
letting the weight of arms and paddle fall. In my own test -- sitting 
on a stool and going through the paddling motion, I'd estimate that 
most of the motion of the paddle blade is downward, with only a small 
amount going back as my shoulder joint forces the arm backward as it 
nears the bottom of the "fall".
>
>> 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.
>
> I addressed this in my video. WHY use big muscles when small muscles
> can do the job? In almost every other activity, we learn to turn to
> the _smaller_ muscles that can do the job, so why not here?

I don't buy your argument from the video. Yes, we use small muscles to 
scratch our heads. They have the more delicate control needed to hit 
the itchy spot. But scratching doesn't require much force. If more 
force was needed, we'd use larger muscles. If force and endurance are 
needed, your fingers, or even your arms, aren't going to make the grade.

If you carve a chicken or turkey for Sunday dinner, you will note 
there is so-called "white meat" and "dark meat". The white meat is on 
the breast: these are the muscles that power the wings for flying (in 
pre-domestication days). The dark meat is the muscles that are used 
for shorted spurts. Your arms are dark meat. They're fine for shorter 
bursts of energy, but they tire after a while. Your core muscles (not 
just the back muscles, by the way) are more like the white meat. 
They're designed for continuous use over longer periods -- like a 
day's paddle.

>>
>> 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.
>
> If you look at my stroke in the video, you'll notice that I have a
> pretty average forward stroke. (It's at 7.50 minutes, and for your
> convenience, here's the link once again:
> http://www.youtube.com/watch?v=-aB0rdn4UnQ ) I'm not promoting a new
> stroke; I'm not urging you to raise the paddle higher. I'm just
> asking: Why DO we raise the paddle that high?
>>
>> 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.
>>
> Why not try? Paddle your boat into the dock, see if you can find the
> vertical rest, and see if you can put it to use.
>
I may certainly do that, once I get my boat back on the water. Again, 
as others have said, it's an interesting point of discussion.

-- 
   Darryl

> Niels
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