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  #1  
Old 03-05-2014
CoachSuzanne CoachSuzanne is offline
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Default Stroking Efficiency, what can we learn from kayaking?

One of the interesting things to me about human swimming is that despite what we would like to think about our stroke, it's impossible to provide continuous propulsion. If we had at least three arms, but likely more, we could always have one arm providing forward movement, but we only have two. in theory then a windmill stroke where one arm begins it's propulsion the moment the other arm stops it's propulsion would be ideal.

However during the stroke itself, the amount of forward propulsion as a vector of applied force, varies consdierably, so that it's simply not possible to provide continuos force acting to move us forward.

Couple that with the fact that the dynamically stroking human creates varying degrees of drag through out the cycle as well.

Minimizing the drag and optimizing the propulsion is therefore the univeral goal of human swimming ... really you could say that about any locomotion.

But the limitations of arms to power movement in a dense medium demands that we examine carefully the relative timing of each movement, and consider how this timing may or may not change with regard to the frequency of applied force, and the balance of net forward energy throughout the cycle.

Bottom line, it's not a ssimple as saying begin the pull immediately. Here is a very interesting slide presentation about kayaking...another surface swimming sport that uses two alternating propelling surfaces.

Interestingly to me, the maximum forward velocity is not occuring at the same time as the maximal forward force. The reason why isn't clear to me, but it tells me that we need to carefully consider what the NON propelling arm is doing at the time the propelling one is spending energy.

I feel like Andy (in Norway) would enjoy this discussion.

Have a look at this slide show PDF, I find it fascinating

http://www.canoekayak.ca/files/54/63...ov_2009_BW.pdf
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USA Paralympic Triathlon Coach
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Steel City Endurance, LTD
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  #2  
Old 03-05-2014
CoachDavidShen CoachDavidShen is offline
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Quote:
Originally Posted by CoachSuzanne View Post
One of the interesting things to me about human swimming is that despite what we would like to think about our stroke, it's impossible to provide continuous propulsion. If we had at least three arms, but likely more, we could always have one arm providing forward movement, but we only have two. in theory then a windmill stroke where one arm begins it's propulsion the moment the other arm stops it's propulsion would be ideal.

However during the stroke itself, the amount of forward propulsion as a vector of applied force, varies consdierably, so that it's simply not possible to provide continuos force acting to move us forward.

Couple that with the fact that the dynamically stroking human creates varying degrees of drag through out the cycle as well.

Minimizing the drag and optimizing the propulsion is therefore the univeral goal of human swimming ... really you could say that about any locomotion.

But the limitations of arms to power movement in a dense medium demands that we examine carefully the relative timing of each movement, and consider how this timing may or may not change with regard to the frequency of applied force, and the balance of net forward energy throughout the cycle.

Bottom line, it's not a ssimple as saying begin the pull immediately. Here is a very interesting slide presentation about kayaking...another surface swimming sport that uses two alternating propelling surfaces.

Interestingly to me, the maximum forward velocity is not occuring at the same time as the maximal forward force. The reason why isn't clear to me, but it tells me that we need to carefully consider what the NON propelling arm is doing at the time the propelling one is spending energy.

I feel like Andy (in Norway) would enjoy this discussion.

Have a look at this slide show PDF, I find it fascinating

http://www.canoekayak.ca/files/54/63...ov_2009_BW.pdf
hey i quickly read through the pdf - where is the graph on velocity vs. force? i only see acceleration vs. force - which sort of makes sense since at max force exerted, it is also encountering a greater drag from water so acceleration declines. i would guess max velocity is here too.
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  #3  
Old 03-06-2014
CoachSuzanne CoachSuzanne is offline
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Originally Posted by CoachDavidShen View Post
hey i quickly read through the pdf - where is the graph on velocity vs. force? i only see acceleration vs. force - which sort of makes sense since at max force exerted, it is also encountering a greater drag from water so acceleration declines. i would guess max velocity is here too.

Argh...it was 2AM when I read this...so maybe i misread the graph!! I'll take a look again.
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Steel City Endurance, LTD
Fresh Freestyle

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  #4  
Old 03-06-2014
kurb kurb is offline
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I am not a kayaker but will relate what one sea kayaker told me a few years ago.

He said: you don't really pull with your arm during the power stroke but push with the other arm using your core , with your foot planted on the pedal

Kinda like swimming
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  #5  
Old 03-06-2014
machelett machelett is offline
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Quote:
Originally Posted by kurb View Post
I am not a kayaker but will relate what one sea kayaker told me a few years ago.

He said: you don't really pull with your arm during the power stroke but push with the other arm using your core , with your foot planted on the pedal
I know nothing about kayaking but I tried to simulate the movement and it immediately made sense to me.
Not sure if I can ever make any practical use of this information but if it saves my life or some else's life one day, I'll let you know! :)
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  #6  
Old 03-06-2014
Ron Bear Ron Bear is offline
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Maximum velocity happens just as acceleration stops. That is what the red line is supposed to represent.

The PDF doesn’t mention the thing that we are all interested in on this forum. Namely how do you do it efficiently? The PDF lists that as a variable, but doesn’t talk about the lessons learned from kayakers and in fact has several pictures of very inefficient form without calling out that it is inefficient.

The most interesting page of the entire thing is the one titled “paddling efficiency”. Note that the slowest three paddlers all achieved 4.8 M/S and the fastest six paddlers all achieved 5.2 M/S. In other words there are only two different top speeds on the graph. But now look really closely at the 4.8 M/S line. This speed was achieved using torques from 5900 N.S all the way up to 8500 N.S. So the rhetorical question is: “for a speed of 4.8 M/S would you rather apply 5900 or 8500 N.S” The real question is what was different?

Competent kayakers can get their speed up to the Froude Limit. The trick to keeping the boat at the Froude limit is to keep your paddle in the water. The three things one can do to keep the paddle in the water are; 1) rapid switch, 2) lengthen stroke or 3) have your partner keep his/her paddle in the water. Lengthening the stroke has the additional advantage that is more efficient for your muscles. How do you lengthen your stroke? This is where kayaking has a swimming analogy. Inefficient paddlers do something called “arm paddling”. You sit bolt upright and move the paddle with your arms. This feels natural and it is how everybody does it the first time they try a kayak. For a longer stroke you bend forward at the waste and reach as far forward as you can (lengthen your vessel?). Your arms hardly move, and you bring the paddle back by using your core (sound like TI?). You go from leaning forward to leaning back like in crew racing. This has the dual benefit that the core can work longer than the arms and also that the stroke is from the front of the boat to the rear.

None of the pictures in the PDF demonstrate this correct form, but a couple of the pictures clearly show guys arm paddling with ginormous arms. One of those guys looks like the Hulk, and I doubt if I would stand a chance in a race with him for 100 yards. I would stomp him in a two mile race though as my core is much more heavily muscled than his (admittedly gigundus) arms.

The Froude limit is a key to another point about kayak efficiency that directly relates to swim efficiency. Look at the PDF chart labeled “Sprint Starts”. Look at every single tall black hump except the first one. Notice something? Every pull but the first one has the boat decelerating at the end of the application of peak power. I want to say that very carefully. The deceleration is not after termination of application of peak power. It is during the application of peak power, but towards the end of it. (The black line is still uber high, but the green line is negative.) This is over pulling. This is the guy pulling 8500 when we already noted that 5900 achieved the same speed. This is exactly the same as swimming while pulling back fast without achieving a good catch. Terry says pull back patiently. If you pull back harder and don’t go faster you would have been better off pulling less. You can totally feel this both in swimming and in kayaking. When you pull smoothly you go fast. If you pull too fast the paddle (or your hand) hits erratically roiling water. For both swimming and kayaking you need to accelerate at the beginning of the stroke, but can’t (and shouldn’t try to) accelerate all through the stroke. After the initial burst of power you should just use the paddle (or hand) to maintain that speed. The maintenance phase is easier than the acceleration phase and in both paddling and stroking you should relish that easy speed.

So yes CoachSuzanne, I agree that there is a lot analogous here. Further I enjoy and am pretty good at both activities and the feel analogous to me. Especially that long easy pull after that snappy switch from left to right.

Ron
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  #7  
Old 03-07-2014
CoachSuzanne CoachSuzanne is offline
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Awesome Ron, thanks for that great explanation!! I am also a paddler. I like that swimming & kayaking each only have two "paddles", as opposed to a motorboat or paddle boat.

I'll reread with your comments in mind. :)
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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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  #8  
Old 03-08-2014
Zenturtle Zenturtle is offline
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Kayaking, cycling, skating, padling on a surfboard, padling on an inflatable matrass, its all more or less the same.
How much variation in speed you are willing to accept before the movement starts to feel less fluent and efficient?
A 10 % variation in speed will not harm the propulsive efficiency much, but a 50 % speed variation will.
Take skating for an example.
When skating on smooth surface, new wheels and bearings, a tailwind or downhill its natural to take looong strokes and balance on the skate going from one side of the road to the other, barely doing anything.
Its possible to skate in this manner because there is little drag that is slowing you down, so you can glide or rest between strokes without a big decrease in speed.
Nice skating, but hey, there is a biker passing you. Can you keep up with the bike?
You start to make deeper, more powerfull strokes, still gliding from one side of the road to the other, but when speed increases, you will notice that you start to decelerate more between your pushoffs.
The gliding part of your skating doesn’t feel so nice anymore, and the biker moves ahead of you between strokes, while you are decelerating.
A new strategy is called for. You start to sit even deeper to decrease drag, and go from one stroke to the other as fluent as possible, minimizing the time between propulsive phases, but at the same time squeezing every inch out your stroke.
It’s the same with kayaking. Keeping your paddle in the water like Ron said.

Its all about drag and relative speed variation.

What is different in swimming, is that you can influence your drag much more than in a kayak or on a bike.
Balance has a big influence on drag. And here is where a compromise must be found between catchup style at one end, and kayak style at the other end.
Catchup style improves balance, which decreases drag, which allows more time between propulsive phases, but at the same time increases the time between propulsive phases.
In Kayak style, the center of gravity of the arms is at shoulder height, not so good for balance.
At the same time the leading arm is going to catch while the other is at the end of the stroke.
A good and fast hook too catch position is needed, otherwise this arm creates drag when body is at maximum speed.
Luckily the speed variation is a bit less while kayaking, so maybe this negative doesnt count so hard.

Different folks, different strokes.
If your balance is very good, you could gain efficiency going a bit more to the kayak side.
Especially when speed (drag) is going up.
When swimming slower while having sinky legs, keep those arms up front to raise legs and decrease drag.

Popov was king of kayak.
Pieter van de Hoogenband (Hoogie) Also experimented a lot with different degrees of stroke overlap. He was not a strong guy. A very technical swimmer.
In fig 1 and 2 you can see the difference in max force during stroke,and timing, efficiency etc etc when he kept the strokemovement the same, but only varied the time between strokes. Going from an strokeoverlap from 0.08 seconds to a 0.08 time time between strokes increased his max arm force already by 20-25% swimming at the same speed.
They also tried a 0.16 sec time between strokes and shortening his propulsive strokelenght.
Knitting the longest strokes as closely together as possible was the most efficient. Look at his speed graph (yellow 2m/sec). It is almost constant.
http://www.tri-experience.com/upload...ie_theorie.pdf

Last edited by Zenturtle : 03-08-2014 at 11:11 AM.
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  #9  
Old 03-08-2014
CoachSuzanne CoachSuzanne is offline
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Nice post ZenTurtle, well articulated and great analogies
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Level 3 USAT Coach
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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