The Isotonic Trap

 Osmosis “is a process by which molecules of a solvent tend to pass through a semi-permeable membrane from a less concentrated solution into a more concentrated one”. It is distinct from diffusion, which is movement from a region of a high concentration to regions with a lower concentration.

What has this got to do with survival, self-defence or any of the other topics this blog has been known to cover? Keep reading and all will become clear.

Suppose you have an orange. You peel the orange and drop it into a vase of water. What happens? After a while the orange begins to swell up as it absorbs water. This is osmosis. The interior of the orange is relatively concentrated with lots of sugars and other molecules. Proportionally its interior is rather low in water compared to the liquid it is floating in. The orange skin is a semi-permeable membrane in that it will let water across but not the larger molecules.

Suppose we take a big bag of salt or sugar and empty it into the water in the vase. If we add enough we may see the orange begin to shrivel. The solutes in the solution surrounding the orange are more concentrated than the orange’s interior so water is being drawn out.

This is a very important mechanism in nature and biology. To give you another example. A freshwater fish is more concentrated than the water it swims in. Its body is therefore constantly absorbing water and the freshwater fish must constantly pee to maintain an equilibrium. The sea fish, however, is surrounded by fluid that is saltier than its body fluids. Water is constantly being drawn from the sea fish and it must constantly drink to avoid “dehydration”.

Some of you may have realized that the concentration of the fluids in the glass could be adjusted so that it matched that inside the orange. There would be no net water gain or loss. Such a condition is called “isotonic”. If an environment is more concentrated than another it is termed “hypertonic” and its less concentrated compliment “hypotonic”.

Isotonic is a word you will have encountered. Many sports drinks are described as isotonic. Very often the marketing of these involves misrepresented facts and sometimes outright “snake oil”.

Sports drinks fall into two categories. The first are “power drinks”, which are effectively liquid food. They are intended to replace energy and salts (aka electrolytes) consumed during heavy exercise. They contain lots of carbohydrate, usually in the form of sugars. There will also be a smidgen of salts and other stuff. Because they contain so many solutes power drinks tend to be hypertonic.

The second category of sports drink are designed to rehydrate the body and replace salts lost from sweating. Some of these drinks are hypotonic. Many promote the fact that they are isotonic. The blurb often says something like “by being in balance with your bodily fluids drink XXX rehydrates you better than plain old water”.

Sound logical? Think back to our orange in a glass. Imagine the orange is the lumen of your gut and the liquid it is floating in is the rest of your body. When the two were isotonic there was no net movement of water! If we wanted water to leave the orange the interior of the orange needed to be hypotonic.

So, are these drinks more efficient than water? There is a grain of truth here but it is often misrepresented. I will need to sketch a crude picture of how the body moves water out of the gut. In essence what the body does is create a very high, localized concentration gradient across the gut wall. It “pumps” sodium ions across the gut wall. This is an active process that requires energy. The energy comes from ATP, which is generally generated from sugars in the gut.. This osmotic gradient created pulls water across the gut wall. Moving small quantities of sodium allows the movement of large quantities of water. It’s a bit like moving a herd of donkeys with a single carrot.

So yes, a little bit of sugar and salt will aid water uptake. But that sugar and salt don’t need to be ingested with the water. Except under extreme circumstances the body generally has sufficient reserves and humanity has managed to rehydrate drinking just pure water for millennia. Carry some raisins or boiled sweets. The replenishment of water and supply of sugars can help offset fatigue.

Taste is another factor. Because they are sweet and/or acidic it is easier for some people to drink larger volumes of sports drink than they would of water, so actual intake of water is higher. There is an interesting experiment that you can try. Take two glasses of water and add just a dash of lemon juice to one. Try each.

It should be obvious that for rehydration you need to drink something that is hypotonic, although a pinch of salt and a little sugar won’t hurt. Drinks with high carbohydrate concentrations will be poor for rehydration, despite some manufacturer’s claims.

Many sports drinks may be isotonic when they are in the can, but is this still true when they reach the gut? Isotonic saline is 0.9%. Incidentally it is useful for soaking bloodstains out of laundry. You can make some isotonic saline by dissolving 4.5 gms of salt in half a litre of water. Taste it. You will find it is way too salty to make a pleasant sports drink. Whilst sports drinks do contain some salt they mainly use sugars to make them isotonic. A body that has been exercising wants sugars and sugars are needed for water uptake, so this seems logical. An isotonic glucose solution is 5% and isotonic sucrose solution is about 9.75%. 47.25 gms per half litre! Yes, that is a lot.

Another factor to consider is that sugars and other complex carbohydrates are mainly digested in the small intestine. They are broken down into monosaccharides such as glucose and fructose and most of them will be absorbed in the small intestine. The majority of water absorption does not take place until later in the large intestine. By the time your sports drink reaches here it will have lost most of its sugars and no longer be isotonic.

Let me return to the topic of power drinks. Most people do not need to ingest calories in this manner. That includes most athletes. You are being subjected to marketing to make you think you are not really trying, not a true athlete, unless you use drink XXX. Taking in lots of calories in liquid from is a bad idea. The lack of solids means that you never feel sated. This is why we have an obesity crisis. People are drinking vast quantities of sugar as soda or fruit juice and never feeling full. It seems likely that even isotonic drinks have way more sugar than they need. You may be drinking more calories than you exercise off!

If you do need a sports drink dilute some cordial and add just a pinch of salt. A friend of mine and myself discovered that “fruit squash” is much more refreshing if you make it very dilute.

I am a qualified biologist who used to try to teach medical students science and physiology. But as always, don’t take my word for it. Do some research of your own, but be wary of advice that is actually just a rehash of marketing. Start by reading the links below.

https://www.theatlantic.com/health/archive/2012/07/the-controversial-science-of-sports-drinks/260124/

http://www2.warwick.ac.uk/fac/sci/moac/degrees/csw/ch934/sports_drinks.pdf

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Cross Stepping Post: Part Two.

Some time ago I started what was intended to be a series of posts on the “Cross Stepping Post”. Part One introduced two of the movements and the intention was to let the reader try these out for a couple of weeks before covering the thing as a whole. As with most of my plans, real life intervened and a year has gone by! Here is part two, the full sequence. (or rather, one side of it!) 

For part two we will only consider the footwork, which is the essence of the thing. There are some hand movements that can be added but it is better to concentrate on your footwork, balance and co-ordination for now.

Begin with your right foot slightly advanced and your left foot angled out. Your spine should be straight, your belly and bum pulled in. Your knees are slightly bent, your shoulders are relaxed and your arms hang down by your sides. Try not to look down at your feet. If you have some familiarity with Tai Chi or other soft or internal martial arts these conditions will be familiar. If you are not familiar with this body condition consult the Tai Chi section of my book or other good works on the subject.

Still with your feet in the starting position it should be possible to lift your right foot from the ground without noticeably shifting your weight. If you are new to this you probably cannot do this. This is one of the objectives you will aim for.

For the second step you raise your right foot and place it behind your left. Your calves should brush or touch. The right foot is raised “flat”, without the heel or toes lifting first. It is placed flat behind the left. This will take practice, so persevere.

For the third stage the left foot is raised and the heel passes down along the inside of the right foot. As the left heel passes the right heel the left foot straightens up. The left foot is brought forwards in a sort of sweeping action and is placed on the ground. The final foot position is a mirror of the start position. You should have maintained your balance throughout this sequence. The chances are you did not, but this will improve with practice.

For the fourth part the left foot is raised and placed down ahead of the right. The lead leg will touch the rear knee. Note that for the previous steps the forward foot has been used. The right/ forward foot is stepped back. The left foot is now the forward foot and is moved in the next two steps.

The next step involves the rear foot, which in this case is the right.

The rear/ right foot makes a semi-circular step forward. Again, lift the entire sole rather than the toes or heel. Place the entire sole down. This move returns you to the start position with your right foot advanced, although you may have changed location slightly.

The next step is the “transition” step. This will take you from a right forward stance to a left forward stance. The action is the same as the fourth step, but in this instance the right foot steps before the left. The rear foot steps forward so that you are back in the starting position, but this time with the left foot forward. You now repeat the sequence on the other side. You left foot steps behind the right. The right then withdraws and advances etc.

Here is the sequence as a single image you can print or load onto your phone.

The Books

 

Hearing Water Temperature!

As regular readers may have noticed, recently I have been perusing several World War Two British manuals. Both the official and the commercially published manuals for the army and home guard place a considerable emphasis on fieldcraft. One aspect of fieldcraft was training the soldier to use his ears more effectively. Langdon-Davies describes a number of demonstrations and exercises a squad may conduct for this purpose.

For the individual he suggests listening to music and trying to follow individual instruments. He also suggests that troops must become familiar with the normal everyday noises of an environment. The noise of sheep cropping grass, the singing of telegraph wires, the noise of cooling stones and so on. By doing this the soldier will better distinguish noises that are out of place, such as a buckle tapping a rifle stock, a branch slapping a steel helmet or a spade biting into dirt.

Aspects of using and training the hearing may be the subject of a future blog. Today I am going to pass on a video sent to me by a regular reader. It is an excellent demonstration of how your hearing may already be giving you far more information than you realised!

 

The Books

 

Facial Camouflage.

Recently I have read books by Tom Wintringham, Bert Levy and John Langdon-Davies. A topic common to all three of these is the visibility of the human face.

If a soldier hears an aircraft overhead it is understandable that he might look up at it. An uncamouflaged human face is visible from a considerable distance so a pilot may observe his observer. Now imagine a company of infantrymen all looking up at an aircraft. Effectively this would be a sudden white flash saying “here we are!”

I recently read that “the secret to invisibility is to freeze like a lizard on a rock”. If an aircraft or other potential threat appears one should take cover if there is any nearby, freeze if there is not. Keep your eyes down on the ground. Only one or two men should observe the aircraft, and then only with adequate face camouflage. In a previous blog post I described a simple framework that could be worn on the back or the pack. These were used by the NVA and Viet Cong when on the march. Any time an aircraft appeared overhead they would drop to the ground and become bushes. Incidentally this also illustrates that marching formations should be irregular.

The following image was scanned from Langdon-Davies’ book.

Langdon-Davies notes that eyes are very distinctive and that many animals have colour schemes that make their eyes less noticeable. Often this takes the form of a line, stripe or blob that runs across the eye. Logically, he advocates that a human soldier’s camouflage should do the same. The human nose is another prominent feature so this needs to be shaded to compensate for this. The scheme he proposes was using a single colour of camouflage, such a burnt cork. It was sufficient to disrupt the palest skinned face. Nowadays multi-coloured camouflage kits are common.

Camouflage creams may have advanced a bit but I have to question if the principles Langdon-Davies had described are being observed. It is not sufficient simply to get the face dirty or paint stripes across it. Prominent features such as the eyes and nose must be disrupted. Features that catch the light must be darkened and areas that are shaded must be lightened.

 

Langdon-Davies was writing for a primarily Caucasian audience but his comments also apply to other skin tones. Human skin can be reflective so needs dulling down. Blue eyes can be distinctive. Shade from suitable headwear can help.

While painting the face can be effective there may be situations where you will need to rapidly remove any facial camouflage. Face painting can be combined with other measures, of course.

A tight-fitting face-net can be distinctive, defeating the purpose of the item. Face-nets or similar devices should be relatively amorphous. In a previous post we saw a face-veil used by German troops. While this was effective it was apparently impossible to run with this fitted. Such factors need to be considered if you have a mobile role. At night a net across the eyes may hinder vision to an unacceptable level.

One of the simplest ways to conceal the face is a scarf or bandana across the nose and mouth. Folds in the material help disrupt the shape. Since the face area may be shaded by headgear I’d go for a relatively light coloured material with contrasting disruptive blobs. As I have suggested in previous posts, children’s clothing or cheap t-shirts can be an economical source of camouflage material.

Even if you have correctly painted your face a cloth across the nose and mouth has other advantages. Facial recognition software has become commonplace in the last few years and we will undoubtable see applications of it more lethal than the camera in your phone. A cloth across the nose and mouth also softens the sound of your breathing, which was one of the reasons the ninja favoured this. A ninja’s disguise might be a simple bandana and scarf. The bandana is folded diagonally and  worn over the hair. The scarf is pulled across the face and tucked up under the bandana. When not worn there would be nothing particularly suspicious about these items.

Make a web search of “ninja hood t-shirt” and you will find numerous sites and illustrations of how to make a ninja hood using a t-shirt or sweatshirt. Many of these are tongue in cheek but it should be apparent to the reader that if you use a shirt with a suitable camouflage pattern you may have the beginnings of something quite practical. Add some scraps of scrim and hessian to further disrupt the shape.

         If you have enjoyed this article or it has been helpful to you please feel free to show your appreciation. Thank you.
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