Winter is on its way, bringing inclement weather and plummeting temperatures. But don’t despair: this doesn’t mean you’re destined for months of treadmill boredom. With the right clothing, worn in the right way, you’ll stay warm, wicked and waterproof when you run outside.
The key to maximising your seasonal efforts is to understand that conditions change. Not only the outdoor environment but also the microclimates between you and your kit.
Modern performance fabrics go some way to solving the problem of regulating temperature and the opposing demands that your body creates. But before you begin stocking your wardrobe, you have to learn how your body regulates its temperature and the ways you can lose or gain heat.
You also need to appreciate the effects of different climatic conditions like rain, wind, and fluctuating temperatures and humidity. These all combine to create a distinct environment that demands a knowledgeable kit outlook.
In dry conditions your body generates enough heat during moderate-intense exercise to tolerate external temperatures as low as -30ºC without the need for excessive clothing. However, if you stop, or if other climatic conditions are thrown into the mix, it becomes a different story.
When your body gets cold your core temperature drops below 37ºC and several things happen. Hairs all over your body rise, blood is directed away from your extremities (hands and feet) and you start to shiver. Your muscles don’t function well at lower temperatures either because they can’t contract as quickly, increasing the risk of injury. Therefore your clothing not only protects you from discomfort and reduced performance but also potential injury.
There are four ways you can lose heat:
1 Conduction Contact between two surfaces.
2 Convection The direction of airflow replaces warm air with cold.
3 Radiation Electromagnetic heat transfer, similar to that given off by the sun.
4 Evaporation Fluid (sweat) is vaporised off your skin or through respiration (expired air is saturated with moisture). This is your body’s best defence against overheating.
So what should you look for when choosing your run clothing? What do windproof, waterproof, wicking and breathable mean, and how do they relate to the weather?
Well, if you want to keep warm, you need insulation. Insulation is simply the heating of trapped air to create a warm barrier between the external environment and whatever’s behind the barrier – in this case, you. Your body naturally insulates itself by standing
its hairs on end.
Animal furs were traditionally used by people in very cold environments for their insulating properties. These days, modern materials allow similar or improved performance at a fraction of the weight and overall thickness, as well as offering improved flexibility. For example, synthetic hollow-core fibres are often used to maximise the trapped air.
When you select an insulating garment, look at the thickness relative to density of the material because this indicates its ability to trap air. Two good examples are Polartec and Thinsulate. Generally speaking, though, two thin layers provide greater insulation than a single thick one.
Striking a balance
But beware: while insulation reduces the effects of the cold, once your muscles warm up and your body starts to generate heat, your skin and core temperatures will rise and you’ll start to sweat.
In this situation you have several options: you can reduce the insulation; you can replace the trapped warm air with cooler air; you can choose an insulating material that deals with sweat; or you can find a balance between all of these options.
The first of these solutions refers to layering but we’ll come onto that later. The second solution – replacing warm air with cooler air – involves convection currents, which can help or hinder your performance.
Baggy clothing, for example, will act like bellows and flap about as you run. The warm air that would normally sit in the fabric is forced out and replaced by cooler air entering your clothing via openings. This is normally undesirable as it wastes the fabric’s insulation benefits, not to mention any aerodynamic properties.
Positive convection cooling is found in devices such as ‘pit-zips’. Such devices allow you to ‘dump’ excessive warm air when necessary through various openings and then close them to recreate the internal microclimate. Look for garments that have a good seal around the neck and cuffs, with mesh pockets to allow air to move freely.
Most fabrics become increasingly susceptible to convection cooling in cold, windy environments where the cool air forces itself into the warm spaces. This is where windproof fabrics like Gore Windstopper come into their own. They employ a combination of fine denier fibres, high-density membranes and knit structures that reduce the garment’s permeability to air. This often allows you to wear thinner, lighter clothing as it’s generally the wind chill that causes most discomfort during winter.
The third point – the handling of sweat – is the most important thing to consider. Sweating is your body’s natural defence against overheating and relies upon fluid evaporating from the skin. This cools your body’s surface and, through conduction, the blood and muscles beneath.
If you don’t deal with the sweat, your clothes get wet and you become uncomfortable as they cling to your body. This reduces your insulation as protective air gaps are filled by sweat. You’ll then get cold as heat is conducted from your skin to the outside environment via the wet fabric, and once your body temperature starts to drop, it keeps dropping.
The main method of sweat removal is called ‘wicking’. High-wicking fabrics transport moisture away from your skin to the outer surfaces of the fabric. Fibres such as polyester, which are mostly hydrophobic, can be treated with a hydrophilic finish to draw moisture towards the outer surface. Similarly, you can create fibres with channelled cross-sections that also control the direction of moisture flow along the fibres using capillary forces. This is the major advantage synthetic fibres have over
Breathability vs waterproofing
Breathable fabrics permit moisture vapour to pass directly into the atmosphere but this becomes problematic when it rains. The waterproofing used to prevent water entry can cancel out the benefits that high-wicking, lightweight fabrics provide.
However, there are some excellent waterproof fabrics that also offer a degree of breathability, Gore-Tex for one. They prevent water penetrating the fabric by repelling it at the surface, and use laminated membranes on the internal surfaces, so smaller, evaporated sweat molecules can pass through. It’s a compromise though, because a totally waterproof fabric can’t cope with high sweat production rates. You need to prioritise either breathability or waterproofing.
So what’s wrong with natural fibres? Well, the primary issue is moisture retention – wool and cotton are naturally hydrophilic materials, meaning they hold on to your sweat. Wool does have excellent wicking properties but the same performance can be achieved with lighter, quicker-drying, synthetic materials.
Layering is key
To optimise your kit selection you must ‘layer’ effectively. Layering involves taking a systematic approach to your clothing. The only problem is that if you prepare for all eventualities, you’ll be carrying a lot of kit. The trick is to check the climatic conditions before you leave the house and take one layer that you can add or remove during your run.
The best way of layering is to use high-wicking synthetic materials next to your skin, then multiple thin layers to provide insulation. A breathable, waterproof outer shell can go on top to keep the rain off.
You must also consider fit. Good-fitting kit reduces undesirable convection cooling. It also reduces drag (loose-fitting clothing increases drag by 5%), and it helps you avoid friction that leads to chafing.
Look out for sensible seam locations or even seamless garments, as each seam presents the potential for discomfort and impeded movement. You should also consider wearing a hat as, although your head represents only 10% of your body’s surface area, it’s responsible for 30-40% of your body’s heat loss. A woollen hat will suffice, though you might want to consider a synthetic solution which will be thinner, lighter and quicker drying. Your hands and feet should also be treated independently. If your hands or feet become wet in very low temperatures, you may be susceptible to frostbite. This isn’t so much of an issue in this country but the use of high-wicking synthetic materials and waterproof shoes will help prevent discomfort.
In terms of these choices, you get what you pay for – the more technical features at a microscopic level, the more expensive the fabric. This is a problem to the purchaser because under normal visual inspection the different qualities of fabric are undetectable. We suggest you dig deep or buy in the sales and carefully read the labels with your new knowledge to hand. Alternatively, companies such as NikWax (www.nikwax.co.uk) can provide hydrophobic and hydrophilic coatings that can be applied to any garment.
The perfect clothing system insulates you from the cold and repels any rain or snow, while remaining fully breathable to enable evaporated sweat to escape without causing uncomfortable wetness. The best advice is to invest in functionally different, quality layers and mix and match these to suit the prevailing conditions you’ll be facing.
Dr Tom Waller is an Ironman competitor and has been working in Sports Technology research for the past nine years
Run jacket A waterproof jacket with a breathable laminate membrane will prevent instant overheating and ensure that your mid-layers stay dry.