A Little Knowledge ...

... can be dangerous, but equally a little of the right knowledge can save your life.

I hope you're finding this blog useful as well as entertaining. In each post I attempt to impart enough useful information to provide you with the knowledge required to understand why we do the things we do in a survival situation. This way, we can make informed decisions as well as use time and resources efficiently. I also attempt to provide information at multiple levels to satisfy those with a more scientific bent. I'm happy to receive comments on posts; not only about their content but also style and detail.

Though survival situations themselves present in multiple and largely unpredictable forms where the nature, environment and resources are varied, the general principals I present cover the overarching concepts which should apply in most scenarios. Sometimes, however, posts will be quite specific. I have recently given some Sea Survival training to the RNLI lifeboat team I crew with, so there is post about that on the horizon.

So, what would you like me to write about? I'm open to suggestions. Please add them in to the comments on this post.

Don't forget, knowledge is only one portion of your training. It's important to get hands on experience in order to get the skills you need to put understanding into action, regular practice is also important so skills are not lost. There are many other Survival and Bushcraft courses available, but do watch out, the quality of some can be shocking. Also, don't always assume that those with a military background are better informed, or better teachers. I was told on one that the rule about drinking urine is that you can drink your own. I didn't even know where to start telling him how wrong they were.

Slow, slow, quick, quick, slow

Whilst researching my most recent post, All Things Being Inequal, I found an interesting set of formulae and some data which had me reaching for a pencil and paper to play with the figures which turned out to have quite interesting results.

Let's start with a question: If you have to go and get something, should you walk slowly or walk quickly? The aim of the game is to minimise calorie loss. Let's assume you've got plenty of water and there would be no additional risks with any of the strategies.

Let's first determine the amount of calories that we burn walking in general. This largely depends on your weight (or more strictly mass), gait and conditions and of course, some combination of speed, distance and time. As your mass, gait and conditions will be the same for each case for this question, we can ignore them.

Within normal parameters of ability (ie. not dawdling or speed walking), it has been shown that  it doesn't really matter how hard you work, the calorie burn is associated with the distance you travel, rather than the actual speed. Put more simply, walk for twice as long at the same speed, you'll burn twice the number of calories. Walk twice as fast for the same time, you'll cover twice the distance and you'll burn twice the calories. Walk twice as fast for half the time, you'll cover the same distance and you'll burn the same number or calories.

Here's the  paper, The mass-specific energy cost of human walking is set by stature.

So, it would seem that it doesn't matter how fast you walk, you'll burn the same calories. However, in a genuine survival situation, one might consider advantages and disadvantages to either strategy. Walk slowly, and you're more likely to spot exciting foodstuffs and useful resources, however, you'll be away from camp for longer, which keeps you away from camp longer, which might include your signals. It's all well and good finding a patch of chanterelle, but if that means you can't light your signal fire when the chopper goes over, then that's a bit of a pain. Maybe consider additional signals on your normal walking routes? Maybe consider moving camp closer to regular resources?

A corollary to this are the considerations about walking up and down hill. If you're walking up hill, it takes more calories, if you're walking down hill, it takes less. This is because you're working against or helped by gravity respectively. Scrambling notwithstanding, it takes the same amount  of extra calories to walk up hill as the amount you save walking down. That is, assuming you are the same mass for each portion of the journey. So, if you're going to go and collect, say, wood, or water, then given no other choice, make sure you walk up hill to fetch it and down hill to get it back. Generally speaking, people will consider water as something they should walk down hill to find, but if you can walk up hill to get it as an alternative, then all the better. Something I've advised people to do on courses whilst collecting wood is to walk up hill to find it and roll it down hill back to camp.

Something that is quite interesting about the research, as the title suggests, is that it shows that calorie expenditure depends not only on mass and distance, but stride length. The longer your (normal) stride length, the less calories you expend over the same distance. This makes sense if you think about how much walking is associated with muscles and how much is associated with pivoting, but this leads to an interesting set of questions about who should go and get the water. Would it be the tall skinny guy, the short fat guy, the short skinny guy, the athlete, the older guy or the child? Well, so long as it's not me, I don't really mind.

All Things Being Inequal

I'm sat here watching Hugh's Three Hungry Boys, which is a slightly disappointing incarnation of a "get from A to B without any money" challenge where, at least in my expectation, there should be a lot more foraging and a lot less scavenging and working in exchange food. However, working for your food itself brought to mind an important concept in survival; that of the inequality.

In mathematics, an inequality describes the relationship between two quantities, stating that one is either less then or greater than the other. So simple is this concept, that we use it every day. If the temperature is less than is comfortable, we turn the heating up. If the amount of money in your pocket is less than the bus fare, tough luck. These are luxuries we might not have in a genuine survival situation, but there is one day to day inequality from the human biology which is extremely important in survival:

calories taken in compared to calories expended

If calories in is greater than calories out, then we put on weight, if less, then we lose weight. From a dieting perspective, the latter makes sense meaning we either eat less to reduce calories in or work harder, increasing calories out. Either way, we're trying to tip the inequality the other way, thus losing weight. In addition, the greater the difference between these two quantities, the greater the rate of weight loss or gain.

In survival situation, it would be unusual for us to find ourself concerned with weight gain, more likely weight loss and more concerningly, rate of weight loss. Loss can be mitigated by reducing calorie expenditure by doing less work, keeping warm and generally sleeping as well as eating more, but here in lies another inequality dressed in a question.

At what cost is in calories is my food coming?

That is to say, are the calories I gain from the food I eat greater than the calories expended getting it? If it costs you more in calories to get the food than you gain from it, then that's a net loss, which is a bad thing. I remember Bear Grylls climbing a huge tree to get a single egg, which is not only a massive risk of injury, but a net loss in calories, which didn't help his cause. An example from the show is that the three chaps did fifteen hours of weeding in exchange for five pounds of vegetable. Was it worth it? Let's see.

Weeding costs about 300 to 350 calories an hour, depending on how much you weigh and how hard you work. The chaps worked pretty hard, so they probably expended about 5000 calories each over the 15 hour period.

I seem to remember the box containing, leeks, turnips, chard, spinach, potatoes and beetroot amongst other, so an average of, say, 50 calories per 100g. That's about 1200 calories in total which doesn't seem to offset the work. The boys were in luck, however, as they were subsequently given a kilo of honeycomb. Whilst standard, jarred honey is around 30 calories per 100g, honeycomb is more like 400. So that's 4000 calories for the kilo. Giving us a total of 5200. Hurrah, we might think, until we realise they had to share it between the three of them, making about 1400 calories each. Damn! Back to a loss.

But, you might argue, they would have used a certain amount of calories anyway. This is true. Each of the  chaps would have burned around 80 calories per hour just sitting around. So, assuming that's not been taken off of the weeding rate already, that's about 1200 calories. How are we doing so far?

calories in = 1400
extra calories out  = 5000 - 1200 = 3800 

so far

calories in are less than extra calories out

For those who saw the show, you might remember that they said one of the advantages of weeding is that you can collect wild food on the way. The really observant amongst you will have noticed one of them with a stalk of chickweed. They also had some stable in the van. So, if we want to flip the equation around, we'd need another 2400 calories in wild food, rice and spuds, which about the amount that an average male needs per day.

In summary, even with the honey and some wild food, they would have been better off, calorie-wise, just sitting on their arses.

This might seem like a contrived, TV example, as is the case with the egg up the tree, but it illustrates an important point about calorie expenditure in a survival situation. It's important to ensure that we waste as little of our calories as possible, by making sure we're always on the look out for foragable food whilst, for instance, combining gathering food with getting water and checking traps. We might consider placing our camp nearer to such daily resources as water, wood and food, in order that we expend less calories walking, which takes up about three times as much as sitting.

In cold weather, we should ensure we make small, efficient fires we can sit close to and reflect the heat in, rather than huge fires we have to constantly go searching for wood for. There's another inequality there. Are the calories I'm wasting keeping myself warm internally greater or less than those I'd expend gathering wood for a fire? If you're walking around all day getting wood for a fire you're not sat next to, you're collecting wood for nothing and wasting even more calories.

This same concept can be applied to water in a low water environment. We use water all the time, but sometimes more than others. Rather than sweat a litre of water in the mid day sun collecting from a small drying stream, it would be better to wait until it's cooler. Is it worth using the water you have to cook rice, or is it better to just drink it, staving off dehydration rather than hunger? Another inequality:

if water in is less than water used then you will dehydrate

The greater the difference, the faster you'll dehydrate and the quicker you'll die.

There's no need for a calculator and calorie counter in a genuine survival situation, just use your head. Limit and combine activities, work efficiently and think. Consciously applying this simple concept of comparing benefit an loss to your actions might save your life.

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