Moisture-wicking clothes act to keep athletes cool and dry. Because exercising in the heat can have a severe impact on physical fatigue, companies promote their moisture-wicking products as the difference-maker in these conditions. However, there has yet to be an independent, peer-reviewed study that conclusively demonstrates that performance apparel improves our thermoregulation and performance. How does moisture-wicking work, how does it affect the wearer, and can it actually provide an edge?
Key Points:
- Moisture-wicking technology uses capillary action to transport sweat away from skin.
- In low-to-moderate intensity exercise, synthetic garments are no better than regular cotton.
- It is possible synthetic wicking fabrics can provide an advantage in maximal and extreme exercise situations, though more research is needed to explore this.
How Does Moisture-Wicking Work?
Thermoregulation during exercise is important in order to balance the heat we produce with an appropriate amount of heat loss. Heat-induced fatigue and increased cardiovascular strain will negatively impact performance and in extreme cases, could have more severe health consequences. When exercising, particularly in the heat, the main way we get rid of the excess heat is by evaporation – by sweating. Clothing acts as a barrier to the evaporation of sweat off our skin and into the air. Moisture-wicking fabrics claim to provide better cooling and thermal balance and by reducing moisture accumulation on the skin, they should also increase the comfort of the wearer.
To “wick” is to use capillary action. It is how water and nutrients travel up a tree from its roots, how water appears to climb up a paper towel dipped in water, and how wax rises up the wick of a candle. Simply put, moisture-wicking fabrics involve hydrophilic fibres (hydro=water, philic=love) that draw sweat away from the skin and through the garment to the outer surface where it evaporates. The evaporation on the outer surface drives the shuttling of more water up from the skin and is also one of the reasons for the one-way-only movement.
Is It Better Than Cotton?
Among studies that examine the influence of synthetic wicking, there is great variability in the exercise protocol type, intensity, and duration; participant fitness and characteristics; garment size, fit, and fiber composition; and measured outcomes. As well, garments, when worn, do not always behave the same way as expected based on laboratory measures: differences that exist between fabrics in the lab may not always be reflected in the performance of a garment in a practical situation. Some studies are also funded by apparel companies, and their study designs or interpretations of results may reflect the source of funding. Considering all these factors, it is not surprising that it is difficult to make an overarching statement about the advantages of moisture-wicking fabric.
Natural fibers like cotton are very absorbent compared to synthetic materials, but are not as efficient in facilitating the transport of moisture to the outer layer to be evaporated. Polyester, one of the most popular moisture-wicking fabrics, while less absorbent, does have this ability to spread and move water vapour away from the skin to help us stay dry. Despite that, in mild to moderate exercise in warm and hot conditions, synthetic fabrics do not provide an advantage over natural fibers in thermoregulation: while some studies found synthetic fabrics resulted in reduced skin temperature, there was no difference in core temperature. Although in some cases, wearing the synthetic garment caused subjects to sweat more, indicating more efficient evaporation, there was no difference in heart rate, or in maximal oxygen uptake (VO2max) either. Subjectively, most participants did not report a significant difference in comfort or in perceived exhaustion between the synthetic and natural garments.
These findings are likely related to our efficient and highly adaptive ability to regulate our body temperature. In most conditions, we are readily able to maintain our core body temperature, and it is suggested that there needs to be a greater stress to reveal any advantages of evaporative fabric. Whether it be through increased exercise intensity or duration, or working in temperatures as hot as 50°C, it’s possible that performance apparel may aid in regulating body temperature only when pushing ourselves beyond our physiological limits. Similarly, studies that did show a difference in participant comfort used protocols that were of higher intensity, with subjects indicating the synthetic fabric as more comfortable and less abrasive.
When Is Moisture-Wicking Synthetic Apparel Preferable?
Synthetic performance apparel can hold onto odours more than its natural fiber counterpart, and often comes with a hefty price tag. Even so, there may be some situations where it is preferable over non-wicking garments. In colder or windier weather, wet cotton close to your skin can create an “after-chill” effect when it evaporates. Like a wet towel on your skin, it may feel refreshing on a warm day, but in colder conditions, it can cause unwanted – and potentially dangerous – heat loss. Activities where there is significant airflow, such as cycling, have greater convective and evaporative heat loss and combined with wetness on the skin, can leave you feeling cold.
In general, it comes down to personal comfort. Because cotton retains more water than synthetic fabrics, it can feel heavier and wetter. Friction of the wet cotton with skin can also cause discomfort or chafing, especially in activities with rapid or repetitive movements, or if equipment is worn on top. Despite marketing implications, there are no known physiological advantages between different brands of moisture-wicking gear. For recreational and most day-to-day exercise, synthetic apparel will help keep you dry and comfortable, but regardless of the brand, will not enhance your performance.
More research is warranted to establish whether there is an intensity or heat threshold beyond which synthetic evaporative fabric will significantly help in maintaining thermal balance. It would also be interesting to explore if activity type, participant sex, or fitness level influence an individual’s response to the garment.