The Role of Sports Clothing in Thermoregulation, Comfort, and Performance During Exercise in the Heat: A Narrative Review

Abstract

The aims of this review are to (1) summarise the current research of sports clothing as it relates to thermoregulation, comfort, and performance during exercise in the heat, (2) identify methodological limitations and gaps in the knowledge base of sports clothing, and (3) provide recommendations for exercise testing protocols to accurately assess the impact of sports clothing in athletic populations during exercise in the heat. Sports clothing consists of lightweight and breathable fabrics, surface treatments, and various designs which aim to enhance sweat evaporation and comfort during exercise in the heat. Sports clothing comprised of natural, synthetic, and chemically treated fabrics has been investigated during exercise of varying durations (15–120 min), intensities (20–70% VO2 max) and types (fixed intensity, incremental, self-paced), and in an array of climatic conditions (18–40 °C, 20–60% relative humidity). To date, few studies have identified significant differences in thermo-physiological, perceptual, and performance measures between natural and synthetic fabrics or compared the effect of chemical treatments to their non-treated equivalent on such measures during exercise. Collectively, previous wearer trials have failed to replicate the upper limit of training and competition demands when assessing sports clothing in endurance-trained individuals who regularly train and compete in hot and humid climates. Clothing comfort has also been evaluated using simple scales which fail to capture intricate detail pertaining to psychological and sensorial parameters. The incorporation of protocols using hot and humid climates (≥ 30 °C, ≥ 70% relative humidity) and longer exercise durations (> 45 min) is warranted. Future research should also consider exploring the effect of sports clothing on thermal, physiological, perceptual, and performance measures between males and females, and assessing clothing comfort using a multi-dimensional approach.

Effect of sportswear on performance and physiological heat strain during prolonged running in moderately hot conditions

“…These findings cannot be attributed to a small study sample size and are in line with previous studies conducted in less thermally stressful conditions and/or at lower exercise intensities, which showed no significant impact of sportswear technologies on well-trained individuals. 19,20,27 In addition to confirming previous findings on physiological heat strain, the present study tested new sportswear technologies such as compression t-shirts and t-shirts with aluminum dots lining the inside of the garment. We found no significant impact on physiological heat strain and running speed at 70% VȮ 2peak in well-trained and national-level athletes.…”

“…19 The majority of these studies primarily focused on the effects of sportswear technologies on physiological responses during very low- 51,52 to low- 31,53 intensity exercise, typically during fixed-rate treadmill running or stationary cycling. 19 Some studies 20,26,27 used moderate-to high-intensity exercise; however, these studies featured short exercise durations, ranging from 25 to 30 min, and were performed in mildly hot conditions (22.1-24.6°C WBGT). For context purposes, the American College of Sports Medicine suggests that environmental conditions ranging from 23 to 28°C WBGT indicate a "red flag," and all runners should be aware that heat injury is possible.…”

“…59 As a result, these athletes might derive greater benefits from increased air velocities that facilitate evaporative heat loss. 60 We chose to maintain a multidirectional air flow of 0.3 m/s (comparable to the level of air flow in the majority of relevant studies in literature 19 ) to minimize variability due to changes in body orientation in real-life scenarios and the fluctuating running speeds inherent in our study protocol. However, we acknowledge that this setting might not adequately represent the diverse wind conditions athletes face outdoors, such as in marathon races or cycling events, where conditions can range from calm to gusty.…”

“…Over the past two decades, many studies have investigated the impact of commercial sportswear on exercise capacity, physiological heat strain, and perceptual responses. 19 The majority of these studies primarily focused on the effects of sportswear technologies on physiological responses during very low- 51,52 to low- 31,53 intensity exercise, typically during fixed-rate treadmill running or stationary cycling. 19 Some studies 20,26,27 used moderate-to high-intensity exercise; however, these studies featured short exercise durations, ranging from 25 to 30 min, and were performed in mildly hot conditions (22.1-24.6°C WBGT).…”

Optimized design of sports bras with pressure comfort, thermal comfort, and shaping support

“…9,17,18 The skin temperature needs to be maintained within a certain range and depends mainly on human metabolism to generate heat and dissipate heat. 19 When the skin temperature is around 32–34°C, there is a comfortable microenvironment between the skin and the fabric. 20 When the skin temperature exceeds 35°C, the heat stored during exercise cannot dissipate, which can lead to skin temperature increase, fever stress, stroke, and even death.…”