Sportswear needs to maintain wearer’s comfort in the outdoors. For this reason, hiking clothing must possess a variety of characteristics and properties that make it reliable, functional, and comfortable. Hence, in order to understand the performance of garments, their characteristics, and properties, it’s necessary to be familiar with the various terms used in the industry.
Professionals and outdoor enthusiasts who are regularly involved in outdoor activities or subjected to extreme conditions are increasingly seeking multifunctional clothing to maintain their comfort in any conditions on and off the trail. Such clothing should keep the wearer dry and comfortable when it’s cold, hot, wet or windy outside. In order to do so effectively, hiking outfit needs to be lightweight, moisture-wicking and quick-drying, water- and wind-resistant, seam-sealed and breathable. Additionally, the garments need to be abrasion-resistant, durable, and to have appropriate thermal insulation properties. All these properties and characteristics of hiking clothing make it functional, reliable and long-lasting – exactly what your apparel needs in order to be able to respond to changing environments.
Essential Terms Related to Hiking Clothing
In order to understand the characteristics of hiking clothing and fibers, it is essential to be familiar with several technical terms:
Absorbency or moisture regain is the ability of a textile to take in moisture, which is the amount of water a dry fiber absorbs from the air when the temperature is 21°C and the relative humidity is 65%. Absorbency is an important property and has a major influence on other properties of textiles. Absorption of moisture causes fibers to swell, changing their size, shape, weight, stiffness, etc. Hydrophilic (i.e. water-loving) fibers absorb a lot of moisture, while hydrophobic (i.e. water-hating) fibers do not absorb moisture at all (or absorb very small quantities relative to their weight). Differences in absorbency lead to differences in functionality.
Table 1: Moisture Regain of Fibers
Source: Materials and Technology for Sportswear*, p.27
There are various features of hydrophilic textiles:
- Hydrophilic fibers such as cotton and wool absorb moisture easily without making the wearer feel uncomfortable. That’s one of the reasons why cotton clothes may be more comfortable in warm weather.
- They accept dyes and finishes more easily than hydrophobic textiles, e.g. hydrophilic textiles can be colored to almost any color, either prior to manufacturing or subsequently.
- They are more easily deformed during processing and use when moist.
- Generate heat while absorbing water. (Do you remember that wool feels warm on the skin when wet?) The heat-generating process stops once the fiber is saturated.
Hydrophobic fibers such as polyester and nylon:
- Have excellent wicking properties. That’s why they’re used for high-performance apparel, in general, and for hiking clothing, in particular.
- Can be less comfortable, though this is compensated by other useful properties such as wicking.
- Resist chemicals and mildew.
- Are stable with respect to properties in wet and dry conditions.
Fibers take water in two different ways. Absorption is when water is drawn into the fiber. Adsorption is when water is held on the surface of the fiber. It’s linked to wicking (though it can also occur if moisture is absorbed within the fiber).
Figure 1: Mechanism of Absorption and Adsorption
Source: Materials and Technology for Sportswear, p.27
Too high absorbency (as is the case with cotton) could lead to negative consequences for the wearer, especially in cold and windy conditions. During relatively intensive physical activities such as hiking and backpacking, the body cools partly by producing perspiration and if the water vapor cannot evaporate to the surrounding atmosphere, it accumulates inside the clothing. The result is that 1) your hiking clothing becomes uncomfortable; and 2) its insulation abilities are reduced, which may lead to hypothermia.
One of the main requirements of hiking clothing is wicking as its function is to ensure optimum microclimate between the skin and clothing. Wicking is the ability of a fabric to transfer moisture along its surface by capillary action. Wicking is typical for both some natural fibers like cotton and for some man-made fibers like polyester and polypropylene.
Wicking of fabrics depends on various characteristics such as structure, construction, density, thickness, finishing treatment, temperature and relative humidity of the atmosphere; though the size of the pores as well as the spaces between fibers related to the capillary channels are probably the major determinants of wicking. For example, synthetic textiles have been made to offer better wicking action than other materials. COOLMAX (a type of polyester fabric) is such a fabric where the capillary action enhances the wicking action.
Let’s outline the wicking process:
- The garment absorbs moisture away from the skin and transports it through the surface.
- The moisture spreads within the fabric structure, absorbs into the outer layer of fibers and is stored there.
- The moisture evaporates from the fabric surface.
Wicking is related to cooling and wear comfort of a particular garment and is one of the most important characteristics of base layers, underwear, liner gloves, and next-to-skin materials. This is explained through the fact that wicking fabrics tend to absorb and spread sweat over a bigger area to facilitate its evaporation and to dry faster. This way, they reduce the discomfort related to wet skin. Moreover, this reduces the continued cooling of sweat on the skin that occurs if moisture remains on or close to the skin.
Proper moisture management is crucial for high-performance activities and it depends on the so-called “breathability“. Breathability is the ability of a fabric to permit the passage of moisture through it (to allow perspiration to escape from the skin to the surrounding environment). If excess body perspiration is not removed from the body, it saturates the clothing. Wet clothing feels clammy and uncomfortable. Moreover, it rubs the skin, which may lead to chafing and blisters.
There are two different ratings that measure the breathability of a fabric:
- Moisture vapor transfer rate (MVTR) is the rate at which a material allows the moisture vapor to pass through. It’s measured by g/m2 per 24 hours. In our post about the types and performance of waterproof breathable clothes, you can see a table with fabric breathability ratings, the breathability levels and suitable activities that correspond to the ratings.
- Resistance to evaporative heat transfer (RET) is another measure of water vapor transmission resistance used for waterproof breathable clothing. Unlike the MVTR, if a company grades breathability using RET scale, a lower value of RET indicates more breathable clothing.
Breathability is measured by determining resistance to evaporative heat transfer (RET); the lower the RET value (starting from zero for a nude person), the higher the fabric’s breathability.
Table 2: Resistance to Evaporative Heat Transfer
Source: Materials and Technology for Sportswear, p.44
The breathability of a fabric depends mainly on the fabric construction and, to a lesser extent, on its properties. As a rule, dense fabrics are less breathable, while less compact textiles are more breathable. Also, fabrics and garments engineered for active use such as softshells and convertible pants are more breathable than garments designed for casual use.
Air permeability is the ability of a fabric to allow passage of air through its surface over a certain period. Ventilation through the fabric is dependent on air permeability, wind, and relative motion of clothed body limbs with respect to their clothing cover. In hiking clothing for cold conditions, air penetration through the garment is brought to a minimum in order to provide wind protection. The possibility for air permeability is related to various design features such as ventilation openings like zippers and underarm vents. Note that despite all features for added breathability, simple hiking shorts have some design idiosyncrasies that make them much more breathable than pants, for example.
The skin accumulated vapor will be able to evaporate if clothing allows ventilation and air circulation. This way, the possibility of a moisture build-up in a garment will be minimized keeping the insulating abilities of the clothing this way. Moreover, ventilation increases heat loss from the skin. In cold conditions, heat loss triggers thermoregulatory control to stop sweating.
Thermal insulation is among the most important characteristics of hiking clothing, especially when trekking at low temperatures. It can be measured in two ways – in terms of thermal conductivity (in Watts per meter-Kelvin or W/m*K) or thermal resistance (K*m2/W).
There has been a tendency related to the reduction of the weight and bulkiness of insulation materials over recent years.
You can see a table with the thermal conductivities of various insulating materials in our post about gloves and mittens for cold protection.
Thermal insulation depends on the ability of a material to trap air inside the core of its fibers; it also depends on the weather conditions (mainly wind and temperature), lining, etc. as the flow through the fabric depends on the pressure difference between the external pressure on the clothing and the internal air layer pressure on the fabric skin side.
As a potential leak point in any waterproof (breathable) garment, seams are usually sealed with a waterproof tape applied to the reverse side of the seam. It replaces stitches that may allow water to enter the garment. What’s more, covering flaps with hook-and-loop closure adds to the water-resistance of the garment making it much less prone to leaking.
Recently, technologies that allow joining of fabrics without compromising their water resistance have been made. The effect is a low-profile seam, which is also flexible and lightweight to provide a performance edge. Examples of bonded zippers, pocket bags and facings are shown in the figure below.
Figure 2: The Anatomy of an Outdoor Hill Walking Jacket
Source: Materials and Technology for Sportswear, p.131
Wearing durable hiking apparel is a must, especially for multi-day trips or multi-week trails. Though the term durability may sound too vague, it’s an important parameter for high-performance apparel and can be defined as a sum of several components: breaking strength, tearing strength, bursting strength, dimensional stability, stretch recovery, abrasion resistance, pilling resistance, and surface friction. Abrasion resistance stands out among them.
The durability of a garment depends on fabric properties and conditions you encounter during wear. There are some weak spots typical for high-performance clothes, including crotch, knees, and underarms. The reasons for this stem in the repeated body movements typical for hiking, walking or running. The manufacturers of quality apparel often reinforce these and some other “weak spots” and areas against abrasion. This way, they achieve two aims: 1) increase the abrasion resistance of the particular area of the garment; and 2) increase the overall abrasion resistance of the garment.
Therefore, durability is determined by the fiber type, fabric, and its properties, and garment construction. Abrasion resistance is the ability to withstand prolong rubbing of fibers against each other or other materials without deteriorating as some fibers have better abrasion resistance than others. For example, nylon and wool have better abrasion resistance than cotton.
There are three main types of abrasion regarding textiles:
- Flat abrasion results from surface rubbing.
- Flex abrasion results from bending, flexing or folding.
- Edge abrasion is typical for fabric edges at collars and cuffs.
In general, fabrics with poor abrasion resistance will wear down and weaken faster than textiles with good abrasion resistance.
Recently multifunctional hiking clothing has become more and more sought after. The challenge is to engineer clothing in such a way that comfort is combined with various other characteristics such as durability, breathability, air permeability, and thermal insulation.
Often, these characteristics and properties contradict each other, and a compromise must be made. What’s important is that the overall comfort level should not be adversely affected by any property added.
When looking for hiking clothing and evaluating its characteristics, don’t forget that the conventional approach to achieving and maintaining comfort on the trail is by using a layered clothing system where each layer is engineered to perform a particular function.
* In S. Hayes, & P. Venkatraman (Eds.), Materials and Technology for Sportswear and Performance Apparel, 2016, CRC Press, Taylor & Francis Group, LLC
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