Bonus Knowledge

Everything here is from my own research, experience and opinion. Others may have different experiences and opinions. All text and photographs Copyright Marc Walton.

Vasoconstriction and Vasodilation

Cold body = cold feet

Vasoconstriction is when your core body temperature drops, and your body constricts the blood flow to your arms, legs, feet and hands. It does this for a very good reason, it does this to preserve the function of your core organs at the expense of your extremities, hands and feet. It is keeping the nice warm blood close to your key organs so you can still function. So, if you are out and you start to feel your hands or feet start to get colder, then it could be because your core is not warm enough. You could throw on another top/jacket or even just a hat may do it, if you don’t have one on.

Now, for this to work you do have to be dressed for the conditions. If you are out in January wearing sandals on the beach and your feet are cold, it is because you are wearing sandals on the beach in January, you would have put on a lot of clothes to keep your feet warm. So, consider this when dressed for the conditions. “If your feet are cold, wear a hat” – Gerry Cunningham.

Cold feet = cold body

I learnt on a first aid course that blood flows to your feet/hands on the inside and then flows back to your heart on the outside. Basically, blood flows down to the extremities and comes back again. So, whatever you have on at the extremities can have an effect on your body temperature.

For example, I once went to the beach in a brand-new pair of rubber boots in winter. On top I wore a jacket that also keeps be warm, no problem. During this brief trip I have never felt so cold on a walk before. I felt cold from the inside, it was horrible. My conclusion was that these boots had 1) come straight from being shipped and stored in cool/cold conditions and held that coldness until warmed up. 2) The boots being rubber had no insulation what’s so ever. My feet were really cold, and so was my body.

Warm feet = Warm body.

I heard another story were a person was out walking in freezing conditions for 3 days. In this time, he had to cross rivers were his boots and feet got wet. However, in his boots he had very good insulation even when wet and his feet stayed warm although they were wet, during this time he also lost his hat and his hair froze. However, he was never cold, and he survived to tell the tale.

Vasodilation

This happens when your body starts to get too warm. When your body gets too warm it increases the amount of blood to the extremities and to the skin surface to help cool off a little. So if you find that you have really hot feet or hands then you could be too warm and you need to cool down a bit. I have experienced this on walks in winter. Once I wore a jacket on a days walk that I kind of new it might be too warm for the day. The temperature was about 5 – 6 degrees C.

Everything here is from my own research, experience and opinion. Others may have different experiences and opinions. All text and photographs Copyright Marc Walton.

What cools our bodies?

Convection, Conduction, Evaporation and Breathing.

When it is cold outside these are our friends, but how can we use them to help cool ourselves down in a hot climate or while we are outdoors during a heatwave?

First, lets understand how these cool our bodies.

1) Convection - This is heat loss by the wind hitting the skin on our bodies. Also by air moving around inside our clothing.

2) Conduction - We can lose heat by transferring our energy to a cold surface, perhaps when sitting on the cold ground, leaning against a cold wall or holding cold items, such as walking poles or ice axes. Even our layers when wet will help us loss heat by conduction.

3) Evaporation - We loss heat from evaporation of sweat or water off our skin. Sweat and water can cool you 24 times quicker than air. Evaporation can be our Friend and Foe, when it hot it is our friend!

4) Breath - We can lose heat from our breath, so just breathing helps us cool down.

I have recently observed Blackbirds in my garden during a heatwave. This mature Blackbird had his beak wide open, I was told that the Blackbird does this to help him cool down. So there you go, during the next heatwave perhaps walk around with your mouth wide open! Join me in the next article that discusses ‘How to prevent flies from going into your mouth during a heatwave’.

So how can we use this information to help us cool down?

1) Convection - If there is a breeze or a wind, expose as much skin as legally possible. The air blowing against you skin will remove warmth from your body. Wearing shorts and t-shirts (keep in mind sun protection), pulling up long sleeves and venting by opening up zips.

Another way is to wear baggy clothes. With baggy clothes you find (A) The larger mass of air in the clothing will not get as warm, as if you had tighter fitting clothes. (B) Being baggy, air in the clothing will move around. You will find the warm air will exit the clothing and cooler air will enter, helping to regulate your temperature.

2) Conduction - If you are stationary you maybe able to find a cooler surface to lay, sit or lean on. If you are moving, it is a little more difficult. Although it is includes evaporation you can use damp clothing. start small like a damp scarf, damp socks (at night), damp hat or if you are really hot a damp/wet shirt.

3) Evaporation - Basically sweat or water on our skin will cool you when evaporation occurs. During evaporation liquid turns into water vapour. When moisture on our skin evaporates, the change that takes place creates a cooling effect on our skin. So assisting evaporation by keeping our skin damp will help. Selecting base layers that will not wick your sweat away is oneway, instead select base layers that aid in keeping your skin damp by pushing sweat back towards your skin. The other option is to use water and dampen or ‘wet out’ your clothes, depending on how hot it is.

4) Breath - Simply walk around with your mouth wide open and prey you don’t get too many flies going in. Seriously though, breathing through your mouth rather than your nose may help you cool down. To be honest this is something I need to be more aware of and try in the next heatwave. I do know that when riding the bike the odd fly does get in!

Clothing to help.

1) Convection - Linen clothing and cotton polo shirts are good ways to get air to the skin because of the fine holes in the material. However, these aren’t considered to be performance outdoor clothing but when you are dealing with much warmer temperatures then they can be good choices. The problem though is that they are not very good or even dangerous if the temperature drops, so they need to be used when the temperature is consistently high.

The other down side is that they could be a problem with sun protection or lack of it. Due to the open structure of the material, sun protection will be an issue. Also, bugs can get through the open material as well.

Another way to get protection from bugs, the sun and also cool down is by using clothing made with a weave rather than a knit. Clothing made with a poly-cotton material such as a shirt, or a windproof made with a weaved nylon can be effective when worn next to the skin. The stiffer material allows air to move around more freely than knitted material, keeping you cooler. Tighter knitted material will trap air and keep air still so it can warm up and in most cases wick the moisture away preventing evaporation, so it won’t help in cooling you.

2) Conduction - Perhaps by wearing lighter weight clothing that are thinner or by removing certain clothing, you may benefit from convection. This way you will make better contact with cooler air and surfaces.

3) Evaporation - The function of outdoor clothing has to be completely flipped upside down when going from cooler conditions to warmer conditions. Instead of removing moisture in cooler conditions it needs to push the moisture back to the skin in warmer conditions. It is down to the individual user to decide when it is the right time or really the right conditions to flip his or her clothing’s function. Having a flexible clothing system that can flip between the two functions of preventing or helping evaporation can be very helpful.

On a days walking adventure you may start in a valley with high temperatures such as in the high 20’s or 30’s C. However, when you reach the summit of the days mountain it might be 10 C and then when you are back down in the valley you are back into the high 20’s or 30’s C again.

The common wicking base layer that wicks moisture away from your body which is vital in cooler conditions will prevent evaporation occurring in warmer conditions.

Some base layers can be worn in such away that they draw moisture back to the skin. This way evaporation can occur and cool you down, these base layers will probably be a technical knitted polyester.