On foam and plates (in running shoes)

On foam and plates

If you're just here for the stats, scroll down to "Results" 

 

(Post still a bit unpolished, but at least it's here)

Getting a surprise

I'd been geeking out over lightweight running shoes, finding and buying racing flats like "New Balance Hanzo s V2" (170 g) and "Saucony type a8" (167 g) on eBay, as they are no longer available from shops. These are both very minimal shoes, with firm cushioning, and c. 10 mm of foam and rubber between you and the ground, these feel incredibly light, and thus fast on your feet (though both are desperately narrow for my feet).

After doing few short runs in these, feeling i put in quite the effort, my partner bought a pair of Puma deviate nitro. That shoe has a nylon plate, and Puma's "super foam". I thought I'd borrow them for a run. They felt super weird, all squishy and I could feel the plate in the shoe, but at the end of the run I'd run really fast...

What to do? I set up a spreadsheet and used meters per heartbeat as a proxy (inspired by fellrnr) for running efficiency. Guess what, my partner's shoes where better than my racing flats - better than any of my shoes...!

Method

I decided on a local loop of 4,5 km with c. 30 m of elevation and ran that route almost religiously every second day until I had a minimum of 5 runs per shoe. The shoe choice was random but biased towards shoes with fewer runs, ensuring I got even number of runs in each shoe, but that the specific order shouldn't be a bias.

The intensity was high for all runs, near threshold, with an extra set of 4 runs at a set heart rate to at least have a single set at equal heart rate. I only used heart rate data from after the first 5 min, to only have steady state in the data.

I further adjusted for my fitness changing (improving) over time, by fitting a 16 day smoothing to the m/beat curve (16 days chosen as this minimised the residuals of the model).

The "score" of the shoe on a given run was the excess m/beat compared to the expected, thus, at least partially, correcting for changes in fitness over time.

As a side note I used my "heart rate reserve" (activity heart rate - resting heart rate) as the heart rate for the activity. This further served to compensate for gains in fitness as my resting heart rate dropped somewhat during the "experiment".

Results

The mean "fitness adjusted m/beat" for the shoes were:

Saucony type a8:         1.98

Scott speed rc:            1.98

Altra escalante 3:        2.01

Puma deviate nitro 2:  2.04

or in charts:

As relative efficiency:

 

And trying my hand at some simple stats in google sheets:

Probability two shoes are equal in in efficiency, two-tailed test, unequal variance. Green indicates <5 % probability.

Shoe Summry

(Useful review of foams)

Saucony type a8

Light classic racing flat with tight fit and firm foam (EVA type, possible with added bubbles). No stability features or rigid structures. The shoe is practically zero drop. This shoe was new during these runs. c. 167 g per shoe.

Scott speed rc

Scotts full supershoe, with high stack height, carbon plate and Scott's fanciest foam (olifin EVA mix) which is very firm. The shoe has slight drop but a very pronounced "rocker" that literally makes you fall/lean forward and want to speed up. This shoe was new. c. 240 g per shoe.

Altra escalante

My normal running shoe. Mid stack height, but zero drop, with roomy foot, that actually is shaped like a normal foot. The foam is TPU based, and is much springier than EVA foam, even after the >500 km I have put into them. c. 260 g per shoe.

Puma deviate Nitro 2

A speedy shoe for short to mid distance, with low drop. The midsole is Puma's "nitro" a TPE material which is very squishy. The shoe has a nylon plate. the shoe was new when I started this. c. 216 g per shoe.

What did i learn?

• Meters per heart beat is quite constant over a range of paces.
• The presence of a carbon/nylon plate makes no difference to my running efficiency.
• More and softer foam is better for running economy (i.e. not EVA).
• A small weight gain (e.g. from 170 g to 260 g) is not significant.
• One can measure small differences, here 3 %, with a simple setup.

A 3 % efficiency might mean:

4:30/km becomes 4:22/km

4:00/km becomes 3:53/km

3:45/km becomes 3:38/km

3:30/km becomes 3:24/km

It's just that racing flats are much more fun...!

Making your lungs last longer - Viking style!

As I've moved to Ireland, this post will be in English (Irish might have been more fitting, but I'm not quite ready for that).
[The introduction is rater long, so skip to "Now starts the magic" if you just want to see the pretty pictures]

Last New Year I was in Norway with a group of alumni sports students from the university I attended in Denmark. Being from Denmark, having ventured all the way to "Rondetunet" (930 m, sat image here), we thought ourselves at quite an altitude. Well into New Years Eve, also here celebrated with some amount of alcohol indulgence, the inevitable happens as we start reminiscing over past mountain experiences - someone has a great idea!
"I wonder if one can counteract the effects of altitude by simply holding ones breath and compressing the lung cavity before exhaling, thus mimicking the pressure found at lower altitudes...?" As it was one of the blokes who came upon this inspired thinking, the question was accompanied with a considerate amount of chin scratching (all danish males have beards, for extra chin scratching effect).

Being scientists, and tipsy, we decided to fashion an experiment to find out just how much (over) pressure one can generate in the lung cavity. The one challenge was to find out how to measure said pressure in the middle of the night, in the middle of nowhere, on a cold Norwegian New Years night.
Que empty box-wine bags. Someone had remembered a bit of physics mentioning something about pressure being equal to force times area. So with an air container at hand, all we needed was a way to measure the force over a know area. Luckily wine box volumes are slightly smaller than the volume of the bag they contain. After cutting out the end of a box (every one has knives this far north) you end up with a box, with one end made up by the wine bag, and a surface are constricted by the wine box. We then agreed that we could measure force by multiplying the readout we could generate on a bathroom scales with the local gravitational constant (9.82 N/kg in Norway).

Now starts the magic.
Having wedged the wine box between a table and the scales so that all force from expanding the wine bag would be directed down through the cut-out bottom of the wine box onto the scales, all the force generated by blowing into the wine bag, should be transferred onto the scales. Because we knew the area of the cut-out and could read the resulting kg off the scales we could figure out the pressure in the bag. Now it was time to blow! Considering the amount of enthusiasm involved when designing the setup, only 4 brave people were ready to blow into the bag.

Figure 1. Pressure exerted as a percentage of sea level pressure compared to the body weight of the blower. Shapes are individuals, they grey zone indicates a rough 95 % confidence interval of the willing population. 

The four! repetitions showed that we could generate 8.9 % of surface pressure (101300 Pa), or 9060 Pa of over pressure (sometimes called gauge pressure). While this is all wildly exiting, it's more fun to know how far up Everest you can go with our newly found technique!
So here we go! The most confusing graph you'll see today:

Figure 2. Partial pressure of oxygen versus altitude. The blue line is the equivalent partial pressure when breathing normally. The red line is the partial pressure equivalent when holding and compressing breath before exhaling .No, I'm not taking into account that earth is an ellipsoid.

In the figure I've added some lines, representing the partial pressure of oxygen at notable height references. "Rondetunet" is the site of idea conception, and while not being very high up, it is a stunning location! "La Rinconada" is a village in Peru, that sits very close the the "Highest Livable Altitude", where one can live a normal (but permanently exhausted) life, with working digestion etc. At 8000 meters is the "Death Zone", over which you simply just start to die...
Here is the interesting part - look at the graph! The red curve doesn't reach the "Death Zone" limit before 10,000 meters! We can all climb Everest without oxygen!

But why don't we then...?

Turns out that while you theoretically can increase the partial pressure enough to survive, you run into a problem of lung size. Because the air you breathe in is not compressed, at 8000 meters you only breathe in 35 % of the molecules you would at sea level. The pressure of that air is roughly 35600 Pa, when you add you squeezing power of 9060 Pa, you not only increase the pressure, you also decrease the volume by 25 %. Of the top of my head the vital capacity for humans is something like 3.5 L, so this compression ratio should not be a problem. What is a problem however, is the aforementioned lack of air-molecules on the intake. Using our "pulmar compression technique" (soon to be patented) you can increase the saturation of you red blood cells slightly, but you cannot take in more air! In other words, the available oxygen per breath at 8000 meters is still 65 % lower than at sea level, no matter how hard you squeeze.
So yes, while you probably could lie still and just breathe quite high up, as soon as you start moving, and you need to ventilate, you'd want to head downhill fast!

There could be a whole section here dealing with falling CO2 concentration and hemoglobin cooperativity, but if you're that into it, go find a university, or have a look on youtube!

Thanks for reading about one of the most fun science experiments I've participated in (there's more of them elsewhere in this blog!)

On the Pettyness of a Big Irish Newspaper

On my way to work this morning I heard something like:
"In todays newspaper we will show you how much more money the 2016 budget means for your pocket!"

This struck me as being the least interesting and petty subject for a newspaper to waste space on.

Before I go on I'll make an assumption:
"The great majority of people are not going to feel any significant difference with the new budget"

In other words I don't think they'd know the cash wasn't there if they hadn't been told...

If the most important thing to think about after a new budget is out is how much difference it makes on your wallet, then frankly, you should go play on the motorway blindfolded (and please don't vote).
The budget is our chance to prioritise what we think is important in the country, by the nature of a national budget it is our money being put to use, and our interest is that it gets put to the best possible use!
Wanting more cash for yourself is fine with me, but if a change to the budget means 100€ extra in your wallet and 460,000,000€ less in the state's pocket (4.6m people in ROI), then I'd rather see what the state can do with that money.

• Teachers are paid 30,000-60,000€ (source), so we could hire 7,500-15,000 new teachers to lift the education. A good investment in the future...?
• Gardai are paind 25,000-45,000€ (source), equating 10,000-18,400 more gardai (not counting cars and kit, but you get the picture).
• Get 4600GWh ~ 850,000 households worth of solar electricity (based on 5,300kWh per year per household, source). this can only be achieved with centralised solar plants, as the price per kWh is higher for small installations (source).

The median Irish buying power in 2012 was 20,000€ (source). This figure is after tax, and is regulated for VAT. I'm using the median value here, as the mean value is likely to be skewed and not representative due to a few high earners.

So what I'm saying is that I think the least interesting thing about the budget is what it means to my wallet. I'll not go hungry, cold or wet because of those changes, but my kids might, if we don't budget wisely, and focus on petty cash

So dear major Irish newspaper, please print some meaningful news, about real issues...!

0 % Unemployment - The Danish Model

None of the knives in this blog post are owned by me (otherwise I could be jailed for writing this).

Denmark has just made its total population criminals. This effectively means that unemployment is over, as we should legally all turn ourselves in. Once we're all imprisoned (for refusing to pay the fine, or owning more than one folding knife), the few people left out can work keeping us in the (very full) prisons...

Suppose you own a knife like this one:

This is the knife "Pingu" from Ansø knives - a lovely knife that is made specifically to be legal to carry everywhere in Europe (according to the general guidelines for cabin luggage in planes, this knife is OK - link here). The blade is non-locking, almost impossible to open with one hand only and measures under 6 cm. from tip to the fulcrum.

But it is now illegal in Denmark - because I can do this:

That knife might be a bit of special knife, but maybe you own one of these (I don't ):

Yup, the wine-opener is a folding knife - and with practice it can be wielded one-handedly as well - making it illegal.

So despair not unemployed people - big mother Denmark will find a way!

To finish this short blog on how to avoid unemployment, I should add that as long as I don't bring it out clubbing, the following knife is perfectly legal (broken phone for scale - blade 35 cm):

Killer whales are not always whale killers...

I was in Iceland in the summer of 2014, and went on a whale cruise with Laki Tours, based out from Snæfellsnes peninsula. They'd had a couple of quiet days, so expectations weren't super high (this is off cause a lie from my side - expectations are always high!) So wrapped in lots of clothes we went out...

Filled with joy over being out, not really caring that we didn't see any whales we started pretending we were there for the birds (this was no act for my girlfriend). We did get to see two puffins and lots of fulmars, but other than that, it was pretty quiet for the first three hours.

Fulmar, a type of gull common to the harsher coasts of north west Europe.

And the best shot I got of a puffin.

Then came the whales

Our man in the sky (a ladder on the mast) shouted that a group of white-beaked dolphins were being hunted by orcas! The only problem was, sometimes the dolphins were following the orcas - not your typical escape strategy. A couple of still pictures to follow...

I could not get the action in pictures so I tried to film it. But only having my old camera with me, quality is wanting (better quality here >200Mb).

As can be seen in the video, the dolphins don't seem afraid of the orcas, They seem to be mingling. Our best guess was that the orcas were a resident pod, specialising in capturing fish, and not interested in marine mammals. I had never heard of orcas working with other whales before, and my excitement was reinforced when the crew on the ship was equally surprised - they'd never seen it before!

Turns out it's not that rare, see here, here and here(.pdf). 

But it's nevertheless very fascinating, mostly on the part of the smaller dolphins. They count on being able to tell the difference between fish- and mammal-eating orcas. So why do this? My guess would be that it increases catch rates for both species. Both pods were small, and could have trouble surrounding or "herding" a school of fish by themselves, but together it would be easier to manage the fish. Especially the nimbler white beaked dolphins could help the orcas with smaller fish. Maybe the tail fluke shock-wave, produced by some orcas, stunning fish, could be the "what's in it" for the dolphins.

One thing is for sure - every time you venture outside you see something new (and every time you venture inside you see what you expect).

Organic farming, why and why not!?

I recently overheard a professor in the Danish radio stating that nutrient load on the environment from organic and conventional farming is equivalent when one takes into account the lower productivity/area in organic farming. This statement provoked me to dig deeper, as I'm an avid pro ecologist. Could I be wrong...?

Nutrients

Plants form the basis for all food production. Some grow wild, and we use animals to convert them into meat/milk that we can consume. Other plants we keep, and eat either directly or feed to animals we then eat. As most of us don't shit where we eat, we encounter a problem with nutrients, especially minerals.

The plants take up minerals (I'll stick to nitrogen, phosphor and potassium here), and store them in their tissue. This bound N, P and K is transported far and wide to be consumed elsewhere, and thus deposited in a concentrated way, often at waste water treatment plants in cities, far from where they are needed by the new crops we need to eat. The Nitrogen we get rid of by de-gassing waste water (denitification), and can be absorbed by certain plants and bacteria on the fields later on. The phosphor is either accumulated in phosphate accumulating organisms, or by chemically treating the water to bind the phosphor in salts. None of these processes bind all the phosphor (5-40 % is removed according to a producer of removal equipment), and much phosphor is released into the waterways and ultimately the sea. The accumulated phosphor can either be used as fertiliser, or be dumped at landfills. 

The problem with especially phosphor is that it's applied to the fields, but doesn't end up there in the end again, it ends up polluting our water. To keep plants growing on the fields we have to get new phosphor in. This phosphor usually comes from mines (especially in USA and China), and is a finite resource. This is a problem for both types of farming.

The organic farmer is not allowed to use a non-biological phosphor source, and has to rely on manure to boost phosphor content of his soil. The manure production however has the same problem as all farmers, they have to get phosphor from somewhere too - suggestions have been made to use phosphor rich seaweed to help close the loop.

Also the organic farmer can leave non-edible parts of the plant (stem, roots) to rot on the field, only removing the phosphor bound in the grains from the field, making the phosphor deficit smaller.

Because of transfer of disease the use of human faeces is often not a good solution to this problem, even though it would close the loop...

What about the carbon?

Carbon, a bit like nitrogen, transfers from us back to the crops as CO2, and is not really a concern in the discussion between conventional and organic farming. Carbon is mostly relevant as a measure of how much energy is used in the production of a given amount of food. Organic farming usually scores better here (lower carbon/food unit), mostly due to the high energy cost of producing artificial fertilisers. Otherwise the tractor of the organic farmer runs the same way the any other tractor does, and can be run on fossil or renewable fuels accordingly.

Yield.

Gross yield is higher for conventional farming. This is true for all industrial scale farming. But what's really interesting is net yield, a kind of input-output balance for farming, and that's when it gets interesting (and relevant).
I've found two long term studies, one from USA and one from Switzerland. The one from the states has run over 25 years and still going. They have equal or better yields from organic fields, with organic plots outperforming conventional during stress, e.g. drought, plant disease. Taking into account the lower cost of production (less purchased fertiliser, less pesticides and less fuel), the organic production is 20 % more profitable (when priced at the same price as conventional produce!).
The Swiss study (21 years) found that their organic plots yielded an average of 84 % of the conventional plots. But the conventional plots received 66 % more fertiliser (NH4NO3 equivs.) and used 40 % more fuel than the organic plots. This mean that the net output from the organic plots were higher than conventional plots - I'll attempt a calculation of how much by converting production and energy use into joules/ha (all numbers from Swiss report).

Conventional plots

 Yield:
5.6 t/ha assuming 90 % carbohydrates, 10 % protein
2828 kJ/mole at 162.14g/mole for cellulose & 17 kJ/g for protein
5600 kg * 90 %                       = 5040 kg
5040 kg / 0.16214 kg/mole     = 31084 moles
31084 moles * 2828 kJ/mole  = 87,906 MJ (from carbohydrates, cellulose)
5600 kg * 10 %                       = 560 kg
5600 kg * 17000 kJ/kg           = 9,520 MJ (from protein)

Total gross yield: 87906 + 9520 = 97426 MJ/ha

Energy use:
360 kg fertiliser at 28 GJ/t (source) = 10,080 MJ
570 L diesel-equiv at 35.9 MJ/L      = 20,463 MJ
And some pesticide that I deem insignificant in the energy budget.

Total energy use: 10,080 + 20,463 = 30,543 MJ/ha

Net Yield:
97,426 MJ/ha - 30,543 MJ/ha  = 66,883 MJ/ha

Organic plots

Yield:
4.7 t/ha assuming 90 % carbohydrates, 10 % protein
2,828 kJ/mole at 162.14g/mole for cellulose & 17 kJ/g for protein
4,700 kg * 90 %                        = 4230 kg
4,230 kg / 0.16214 kg/mole      = 26089 moles
26,089 moles * 2,828 kJ/mole  = 73,778 MJ (from carbohydrates, cellulose)
4,700 kg * 10 %                        = 470 kg
470 kg * 17000 kJ/kg                = 7,990 MJ (from protein)

Total gross yield: 73,778 + 7,990 = 81,768 MJ/ha

Energy use:
122 kg fertiliser at 28 GJ/t (source) = 3,416 MJ -> 0 MJ  (comment on this below)
340 L diesel-equiv at 35.9 MJ/L      = 12,206 MJ
No pesticides, and all organic fertiliser (manure), meaning no costly ammonia-production.

Total energy use: 0 + 12,206 = 12,206 MJ/ha

Net Yield:
81,768 MJ/ha - 12,206 MJ/ha  = 69,562 MJ/ha

So with no pesticides, the net yield from the organic plots were 4 % better in the Swiss study.
I will admit that prior to me doing this calculation, I thought organic would win by more, but this just goes to show that one can easily be confused by percentages.

According to these two studies organic farming clearly comes out as the most profitable.
I know some people who would argue that I cannot simply use net joule output, as we cannot eat "diesel joules", and spending fossil fuel to create "food joules" is a net gain. This is true, but using less fuel means it'll last longer, and we don't have to replace our old tractors with new electric ones as soon, if we spend less fuel. The fossil fuels will run out.

Health

With regards to the health side of things there's a lot of mixed messages out there.
A few hard facts though are:

• Limits for residues are often based on what we can detect, and not on whether or not it's harmful to ingest.
• Even though most conventional produce is well within the above mentioned levels, sometimes this is not the case.
• Limits for residues are set per compound and often not as a total residues value, this means that if three pesticides are present in your food, and each one is under the limit, it is approved. But studies show that pesticides can show additive effect, meaning that 1mg of "A", "B" and "C", has the same adverse effect as 3mg of either "A", "B" or "C". (suppose a limit of 2mg).
• Organic produce does not contain pesticides (other than what the wind has carried).
• Residues of pesticides severely damage ecosystems and humans - read the wiki entry on this.
• Check out this video!

Sources:

• www2.mst.dk/Udgiv/publikationer/2004/87-7614-284-1/html/helepubl.htm (Danish)
• http://www.inra.fr/en/Scientists-Students/Food-and-nutrition/All-reports/Cocktail-effects-of-toxic-substances/The-cocktail-effect-of-pesticides (Cocktail-effects)
• http://infohub.ifoam.bio/sites/default/files/page/files/misconceptions_compiled.pdf (General info)
• http://www.theguardian.com/world/2014/apr/29/french-children-farms-vineyards-exposed-dangerous-cocktail-pesticides (non-food contamination)

I might update this post as I learn more, or if I'm corrected.

As always, please leave a comment.

Racism

This might be dangerous territory - but so much more important because of it.
(Please comment on this post)

I'm from Denmark, and although I'm not proud of the way politics have turned in the past decade (very xenophobic), I'm still inclined to think that we are a kind and tolerant people.

The other day this was challenged by and Irishman, who in particular did not like our use of the word "indianer" (similar to the English "indian", but with a slightly different meaning).

The discussion lead to these two questions:

1. Is it racism if you use a common (non derogatory) word to talk to others about a non-present ethnic group who finds the word derogatory?
2. Or do you become a racist if you use words that are non-derogatory to you, used in a non-derogatory way, but perceived to be so by a third person?  

In both these cases I think the answer is no.

Some further thoughts on this:

In Danish the word "indianer" means: 

"Person belonging to an ethnic group that together with inuits and aleuts are the indigenous people of the North and South America". (picture)

In English, this is what an American-Indian is:

"A member of any of the aboriginal peoples of the western hemisphere except often the Eskimos; especially :  an American Indian of North America and especially the United States".

(Merriam-Webster)

So the definitions don't line up completely; the English definition does not include Eskimos, and is emphasising the native Americans of north America to a higher degree. An Indian is thus only a person from India.

The discussion was mainly about whether or not it was racist to use the (Danish) word "indianer" when talking about the indigenous people of South America.

My own opinion on the matter lies very close to the following (taken from the introduction to ethnic slur on wikipedia):

"For instance, many of the terms listed below (such as "Gringo", "Yank", etc.) are used by large numbers of human beings in many parts of the world as part of their ordinary speech or thinking without any intention of causing offence, and with little or no evidence that such usage does in fact cause much or indeed any offence, while the implicit or explicit labeling of such large numbers of people as racists (or similar terms such as prejudiced, bigoted, ethnophobic, xenophobic, etc.), simply because they use some words on the list below, can itself be deeply unfair and insensitive and can thus cause deep offence".

So among Danes there's no issue here, but when you mix it up a little and add a Swede and an Irish to the company things get more interesting. They will now perceive the Danes as being insensitive and racist - who's right here? Can all Danes be deemed racists just because the same word has a different meaning abroad? 

There are words of cause, where even I know not to use the Danish word outside conversation with ethnic Danes. E.g. it's safe to use the Danish equivalent of Negro in Denmark, it's spelled "neger" and just means that your ancestors lived within 20-30 degrees of the equator. This is backed by multiple court rulings, and not my just my opinion.

Racism by naming/labelling 

It was pointed out that maybe it has to do with who comes up with the name. If you don't yourself come up with the name given to you, it is racist to call you by it, if you have your own name for yourself. A little reading on etymology reveals that almost no ethnic group carries a name they chose for themselves. This makes sense as names for ethnic groups are usually needed to talk about the group, which is a thing most often done by people not in that group (if you're in the group "us" suffices). 

I certainly don't think of myself as a racist, and surely you're only a racist if your actions (or words) causes harm? - with or without intention.

Please leave comments