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View Full Version : Min strokes per length != max efficiency?



LindsayNB
February 25th, 2010, 12:50 PM
Swim smooth has an interesting pair of videos that makes the argument that minimizing strokes per length isn't the same thing as maximizing efficiency. Janet Evans and Laure Manaudou are cited as examples of swimmers with high strokes per length and a faster turnover. Elite triathletes with shorter strokes are also cited. The idea is not to advocate everyone use a shorter stroke but just to say that if a shorter stroke works for you don't throw that away in pursuit of lower strokes per length.

I wonder if swimming with a shorter stroke and higher turnover is analogous to using a lower gear when cycling (spinning versus grinding). People generally acknowledge that the optimal gear to use will vary from individual to individual. Extrapolating from that line of reasoning, perhaps elite swimmers using longer strokes do so because they have greater strength/more power that allows them to use a longer stroke/higher gear rather than because they worked on lengthening their strokes (although the two are clearly related).

YouTube- Swim Smooth: What Is An Efficient Freestyle Stroke? Part 1

YouTube- Swim Smooth: What Is An Efficient Freestyle Stroke? Part 2

tomtopo
February 25th, 2010, 01:20 PM
The efficiency of a swimming stroke is dependent upon many variables but some of the biggest variables are these:

1. Body size, height, weight, strength. The height of the person dictates the number of strokes they need to take to attain the same speed of someone taller (everything else being equal). The weight in proportion to the height takes on the same consequence (more rotund = more strokes).

2. Efficiency of the stroke itself. If the stroke pattern is efficient less strokes are needed to maintain the same speed (everything else being equal) and vice versa.


3. I do agree that some swimmers need to take more strokes to make up for other deficiencies. When everything is equal stroke efficiency is the trump card differentiating the best in the world from the rest of the world.

LindsayNB
February 25th, 2010, 02:06 PM
I guess that the interesting point for me was that, as you say, a more efficient stroke will result in fewer strokes per length but at the same time fewer strokes per length is not necessarily more efficient in terms of effort.

I wonder if some people are physiologically better able to use a stroke with a higher turnover in the same way that I would expect that a lower gear would work better for one person where someone else would do better one gear up in cycling.

Leonard Jansen
February 25th, 2010, 03:20 PM
Efficiency is the least amount of energy expended for a given speed over a given distance. The idea that there is a one-size-fits-all technique for all people for all distances and efforts is a bizarre notion that swimming just can't seem to shake. Even racewalking left that idea behind almost 40 years ago. The laws of physics are the same for everyone; the optimal application of same is different for everyone.

-LBJ

thewookiee
February 25th, 2010, 03:38 PM
. The idea that there is a one-size-fits-all technique for all people for all distances and efforts is a bizarre notion that swimming just can't seem to shake. Even racewalking left that idea behind almost 40 years ago. .

-LBJ

One of the most sensible things I have read on this forum.

fritznh
February 25th, 2010, 10:33 PM
One of the most sensible things I have read on this forum.

I agree that each person will have their own optimal stroke count. We're all built differently and will have somewhat different mechanics. Physiologically different people might also be able to sustain a higher turnover or higher power output than average.

I'd maintain that the basic mechanical motions will still be the same, though, and that the key ideas are minimize drag, maximize propulsion. Stroke length will differ, some people have shorter arms and may be able to sustain a higher turnover without increasing drag, but a nearly optimal basic swimming stroke will be similar with most people.

Jazz Hands
February 26th, 2010, 01:47 AM
Kicking seems to be a big part of it. Manaudou and Evans both used light two-beat kicks. Swimmers who appear to glide more are actually coasting on a powerful kick. Ian Thorpe is a good example.

thewookiee
February 26th, 2010, 08:14 AM
Kicking seems to be a big part of it. Manaudou and Evans both used light two-beat kicks. Swimmers who appear to glide more are actually coasting on a powerful kick. Ian Thorpe is a good example.

And very few people are able to develop a kick like thorpe, hackett, biedermann. The rest of us probably shouldn't focus on trying to glide the way those guys do.

mj_mcgrath
February 26th, 2010, 09:14 AM
So how does one measure efficiency? Fewest strokes, fastest time for a given distance-- like swim golf? It it 1. or 2. below?

1. If it takes me 80 seconds and 50 strokes to swim 100 yards, it is more efficient if I take 48 strokes and still maintain that 80 second pace?

2. Or is it more efficient if I take 50 strokes and improve my time to 78 seconds for 100 yards?

I always thought it was 2 and I don't have any basis for that other than an old post by Paul Smith wherein he described how he descends 25 yards while maintaing the same SPL:

So after all the endless discussions on this topic....and the challenge in trying to "coach" in writing I actually found myself helping out a local pro triathlete last week with just this thing.

As is the case on this forum and other times I've attempted to explain; catch, rotation, lengthening of stroke, maintaining stroke while accelerating, etc. I found again that some folks have a "natural" sense of feel for this stuff....its VERY hard to coach feel.

So.....I spent yesterday breaking down my stroke wit assistance from Jane Scott (Boulder Coach) and trying to better explain what it is I do unconsciously that others have to think about...some observations:

- In a series of 25's (all from a push) I tasked myself with keeping 11 strokes per lap and to descend each 25 till I added a stroke.....my goal to see what changed.

- First observation....I can literally slip my hand/forearm/arm thru the water without feeling any sense of "pressure" and take 11 strokes as slow as 25 seconds.....I can accelerate and descend down to 12+ keeping the same 11 strokes....faster than that my kick "kicks in" and I add another stroke and get to the low 11 range.

- What was different? First thing I noticed is that although it seems my hand track stayed the same on each 25 there was an ever increasing sense of "pressure" I could feel as I got faster. I would equate the sensation change as dramatic as moving my hand thru air on the easiest 25 to literally feeling the sensation I would feel pushing on the wall to climb out of the pool.

- So what happened? First I was able to discern a "tensioning" of my arm...but further examining this with Janes help it became apparent that this "coiling like a spring" as she described it was coming from my core....very interesting to really focus on this and realize how much that changed everything.....from there it extended to my catch....and ultimately the entire stroke movement thru the water.

- What next? We asked a few other swimmers to work on this as well and t change their focus to their core and it was amazing that all of them said the same thing....they could not feel anything in that area...when we asked to try and tense it resulted in other parts of the stroke falling apart...

- Thoughts for now; I really do think that to change these things takes an incredible amount of breaking down the stroke via drill work as has been discussed over and over here...the difference is really taking the time to think specifically how these drills translate to actually swimming...so many people I see do drills without a real sense of their purpose.

I think the key drills for me at this stage continue to be variations of sculling, the "arrow" drill shown on a link in an earlier thread that U of A uses and head up swimming (tarzan).

swimcat
February 26th, 2010, 10:07 AM
If i take 14 strokes, i am super slow. I am usually at about 16. if going fast wow, 18. I am not a freestyler. for breasstroke- super slow (like practice 8). realistically more if pushing it.
I always heard, less strokes, more efficient but the people faster than me in practice take 20 or more. go figure.
worst stroke- back for me, is like 19 eek

rtodd
February 26th, 2010, 11:35 AM
Here is how you minimize strokes per length and maximize efficiency.

http://www.floswimming.org/videos/swimming_race/play/7422-

Jazz Hands
February 26th, 2010, 02:14 PM
So how does one measure efficiency? Fewest strokes, fastest time for a given distance-- like swim golf? It it 1. or 2. below?

1. If it takes me 80 seconds and 50 strokes to swim 100 yards, it is more efficient if I take 48 strokes and still maintain that 80 second pace?

2. Or is it more efficient if I take 50 strokes and improve my time to 78 seconds for 100 yards?

We're talking about whether increased SPL with all other factors equal necessarily means more efficiency. There is a possibility that few swimmers or coaches ever consider: neither #1 nor #2 which you listed is right.

In both cases, you could be getting less efficient. In an absolute sense, #2 is definitely a decrease in efficiency, since faster swimming is almost always less efficient due to drag. Especially if you get to this point by trying to stretch your stroke, or by kicking harder. Relative to speed, you might be increasing your efficiency in scenario #1 or #2, but the whole point of this thread is that SPL can increase via methods other than efficiency.

Leonard Jansen
February 26th, 2010, 02:25 PM
So how does one measure efficiency? Fewest strokes, fastest time for a given distance-- like swim golf? It it 1. or 2. below?

1. If it takes me 80 seconds and 50 strokes to swim 100 yards, it is more efficient if I take 48 strokes and still maintain that 80 second pace?

2. Or is it more efficient if I take 50 strokes and improve my time to 78 seconds for 100 yards?



Neither. The only way to measure true efficiency is via testing oxygen/energy usage at a given speed for a given distance.

Examples (non-exhaustive) of why each of the above can be misleading:
1. I can swim 25 yards in 14 strokes pretty readily for most paces. I could also do that 25 yards with 11 strokes at most of those speeds if I really concentrate. However, it takes me more energy/effort to do so. Therefore, I am
less efficient at 11 strokes since it took me the same amount of time but more energy/effort.
2. You may be able to hold the same stroke count and drop time by maintaining the same effort with the arms, but adding a stronger kick. (I can't - my kick is worthless.) The energy used for the arms is the same, but you've also added energy with a more vigorous kick and so calling it more efficient is misleading.

My own rule-of-thumb for efficiency is that if I can cover a given distance at a given pace with less fatigue than I have previously, then I have become either biomechanically or biochemically more "efficient."

-LBJ

makesense
February 26th, 2010, 02:31 PM
one can get technical

efficiency = useful power output divided by total power input

ie, what are you getting for what you are putting in

question is, what's your measure.....strokes per length, distance per stroke, or speed or time to the finish?

hard to pin down things that are changing, particularly regarding input power/energy

perhaps time to get to finish with an all out swim may be the most meaningful estimate of efficiency

(power = work divided by time)

(work = force times distance traveled)

LindsayNB
February 26th, 2010, 03:39 PM
one can get technical

efficiency = useful power output divided by total power input

ie, what are you getting for what you are putting in

question is, what's your measure.....strokes per length, distance per stroke, or speed or time to the finish?

hard to pin down things that are changing, particularly regarding input power/energy

perhaps time to get to finish with an all out swim may be the most meaningful estimate of efficiency

(power = work divided by time)

(work = force times distance traveled)

I think the point here is that, as you say, efficiency is measured in terms of energy expended, and none of strokes per length, distance per stroke, or time for distance measure energy expended directly.

The problem is that it is hard to measure energy output directly. I think your assumption is that in two all out swim of a given distance by a single person the total energy expended by an individual will be the same so the faster time will indicate greater efficiency. This would imply that instead of counting strokes in an effort to get more efficient that we should track our interval times instead.

Alternately one could test the duration for which one could maintain a given pace using two stroke variations, and the greater the duration the more efficient that stroke variation must be.

That brings up the question of the relative advantages of stroke counting versus monitoring speed or duration...

Jazz Hands
February 26th, 2010, 03:59 PM
My own rule-of-thumb for efficiency is that if I can cover a given distance at a given pace with less fatigue than I have previously, then I have become either biomechanically or biochemically more "efficient."

I like this. It follows that the ultimate measure of efficiency is race speed. If you have made a technique change that might be more efficient, test it by going all out for time. Since, with more efficiency, a given pace takes less out of you, you'll go faster at the limit of fatigue.

makesense
February 26th, 2010, 07:19 PM
LindsayNB and Jazz Hands....

righto

SolarEnergy
February 27th, 2010, 12:35 PM
Neither. The only way to measure true efficiency is via testing oxygen/energy usage at a given speed for a given distance. I know what you mean here. I have to agree to a very large extent here.

However, there's an other very simple and logical way to assess improvement in Swimming Efficiency for beginners to intermediate swimmers. Any drastic improvement in times, that are not attributable to drastic improvement in fitness can be considered as an improvement in swimming Efficiency.

I'm currently helping a bunch of intermediate level triathletes to improve over 1500. Most sets are designed to improve technique/pure speed. Most candidates have improved by more than 2min so far. Most report being able to swim much faster with less efforts. That is improvement in Swimming Efficiency. No need for lab testing here. Lab testing would only be required to Quantify this improvement.
- - - -

That said, in order to better assess your improvement in Swimming Efficiency, you have to count your strokes. How many of you can claim being aware all the time, no matter the set duration and intensity and complexity, including racing situations, how many can claim being aware of the stroke count?

Then once you are used to be aware of your stroke count (at any time in any situation), you have to evaluate the change in DPS by assessing the duration of the glides prior turns. Then you're set. You're in a position to find your DPS/Stroke Rate optimal balance.
- - - - -

Lindsay, yes this paradox can be compared with Cycling Gear/Ratio. However, we have to bare in mind that swimming is a Glide based cyclic activity. We (like speed skater, or skiers) benefit a lot from overgearing whilst training (that is, swimming most slowish volume on a stroke count diet).

Performing base mileage on a severe stroke count diet remains the best way to develop race pace specific muscle attributes whilst booking lower intensity mileage. I don't think that this approach is an option for cyclist or runners (these guys don't glide).

Karl_S
February 27th, 2010, 12:56 PM
The videos are fascinating. Thanks to the OP for posting.
I am suspicious that hand size, or more correctly the
cross-sectional area of the hands and forearms is closely
related to stroke count; smaller hands => more strokes.
To support this hypothesis, I note that with hand paddles
stroke count often goes down. If you have small hands
you simply have to condition yourself to be able to
maintain a higher stroke count if you want to swim fast.

mj_mcgrath
February 27th, 2010, 01:23 PM
Any drastic improvement in times, that are not attributable to drastic improvement in fitness can be considered as an improvement in swimming Efficiency.

SolarEnergy may be right. However, the 1500 time improvements by the triathletes may be a result of an increase in BOTH efficiency and conditioning. How would you possibly separate the two?

The point brought up by LindsayNB and the videos is a good one--min. strokes per length does not necessarily mean max efficiency or produce max speed. The Swim Smooth videos and SolarEnergy suggest that everyone has an optimum and unique stroke rate/distance per stroke. Stroke counting helps find it.

I would suggest that it's not a static number but subject to change due to better swim technique and/or better conditioning.

SolarEnergy
February 27th, 2010, 01:28 PM
The videos are fascinating. Thanks to the OP for posting. Paul Newsome is one of the top coach in the world for teaching/training triathletes. He founded and operate SwimSmooth. He is, among other thing, responsible for this great technological breakthrough which he called: Mr.Smooth. He developed this concept in collaboration with an extremely talented engineer called Adam Young.

ref. Swimsmooth's website: www.swimsmooth.com
ref. Mr.Smooth: http://www.swimsmooth.com/console.php
ref. Wetronome: http://www.swimsmooth.com/wetronome.html

Besides, Paul is extremely kind, and pretty affordable too.