S. Wenger, R. Csapo, M. Hasler, B. Caven, T. Wright, T. Bechtold, M. Faulhaber, W. Nachbauer

❙ Sebastian Wenger, Robert Csapo, Michael Hasler, Barnaby Caven, Tom Wright, Thomas Bechtold, Martin Faulhaber, Werner Nachbauer ❙

Effects of different moisture management properties of commercially available hiking jackets on physiological parameters during leisure hiking

Auswirkungen unterschiedlicher Feuchtigkeitsmanagements kommerziell verfügbarer Wanderjacken auf physiologische Parameter während des Freizeitwanderns

ZUSAMMENFASSUNG

Wasserdampfdurchlässige (WVP) Bekleidungssysteme verbessern den Tragekomfort, indem sie Feuchtigkeitsansammlungen reduzieren. In warmen Umweltbedingungen kann sich WVP Bekleidung zudem positiv auf die Leistungsfähigkeit beim Sport auswirken, da sie den Anstieg der Körpertemperatur begrenzt sowie Energieverbrauch und Schweißproduktion senkt. Bezüglich der Auswirkung von WVP Bekleidung auf die Leistungsfähigkeit in kalter Umgebung ist die Erkenntnislage dagegen unzureichend. Darüber hinaus ist ungeklärt, ob sich die Erkenntnisse aus der Grundlagenforschung auch auf kommerziell verfügbare Wanderjacken übertragen lassen, welche sich nicht nur hinsichtlich ihrer Durchlässigkeit für Wasserdampf, sondern auch in Schnitt und Design unterscheiden. Um die Auswirkungen kommerziell verfügbarer Wanderjacken mit unterschiedlicher Wasserdampfdurchlässigkeit und unterschiedlichem Design auf Feuchtigkeitsmanagement und physiologische Parameter zu untersuchen, absolvierten zehn männliche Probanden eine simulierte einstündige Wanderung (Gehgeschwindigkeit 3,5 km/h; Steigung 15%) mit anschließender Erholungs-

97

phase (15 min) in einer Klimakammer (12°C, 40% relative Luftfeuchtigkeit). Die relative Luftfeuchtigkeit im Bekleidungssystem wurde dabei kontinuierlich gemessen und Mittelohrtemperatur, Herzfrequenz sowie Gewichtsverlust der Probanden wurden als physiologische Anstrengungsparameter erhoben. Jacken mit einer höheren Durchlässigkeit für Wasserdampf wiesen eine niedrigere relative Luftfeuchtigkeit im Bekleidungssystem auf. Darüber hinaus war die Gewichtszunahme der entsprechenden Jacken und der restlichen Testbekleidung geringer. Auf Schweißverlust, Herzfrequenz oder Mittelohrtemperatur wirkte sich die Wahl der Jacke dagegen nicht aus. Unsere Ergebnisse zeigen, dass Jacken mit einem verbesserten Feuchtigkeitsmanagement zu einem trockeneren Mikroklima beitragen, was sich gegebenenfalls positiv auf das Tragegefühl auswirken kann. Allerdings wurden keine signifikanten Unterschiede hinsichtlich der physiologischen Anstrengungsparameter gefunden. Dies legt nahe, dass die Wahl der Wanderjacke keinen Einfluss auf die Leistungsfähigkeit während einer simulierten Wanderung in kalter Umgebung hat. Schlüsselwörter: physiologische Belastung, aerobe Belastung, Textilien, Durchlässigkeit

SUMMARY

Water vapor permeable (WVP) clothing systems improve wearing comfort by reducing moisture accumulations. In hot environments, WVP clothing properties may also benefit exercise performance by limiting rises in core temperature and associated sweat loss and energy demands. Scant research exists to test the effects of WVP properties on exercise performance in cool environments. Further, it remains unclear whether findings from basic research are also applicable to commercially available hiking jackets that differ not only in WVP properties but also design features. To evaluate the effects of commercially available hiking jackets differing in WVP properties and design features on moisture management and physiological parameters, ten male subjects performed a simulated 1-hour hike (walking speed 3,5 km/h, 15% of inclination) with consecutive rest (15 min) in a climatic chamber (12°C, 40% relative humidity). Relative humidity in the clothing system was continuously recorded and tympanic temperature, heart rate and weight loss were measured as parameters reflecting physical effort. Jackets featuring better WVP properties led to lower relative humidity in the clothing system and associated weight gains of jackets and remaining apparel. No significant effects on overall sweat loss, heart rate or tympanic tempera-

98

ture were found. Our results suggest that jackets featuring improved moisture management properties facilitate a drier microclimate, potentially benefitting wearing comfort. However, no significant differences in parameters reflecting physical effort were found, suggesting that the choice of jacket does not influence exercise performance during a simulated hike in a cool environment. Keywords: physical exertion, aerobic exercise, textiles, permeability

INTRODUCTION

Hiking in the mountains is one of the most popular leisure activities in alpine regions, mostly practiced by elderly, well-situated people with a health-orientated lifestyle (1,2). To address this target group’s needs, the outdoor industry offers a broad range of products. A central demand is protection from the prevailing weather elements. Here, hikers can mostly choose between favorably-priced, non-water vapor permeable jackets with polyurethane coating, 2.5 layer jackets with water vapor permeable (WVP) membranes composed of e.g. polyurethane in a medium price range, and high-end three layer products employing WVP membranes made of e.g. stretched polytetrafluorethylene (PTFE). For improved micro climate, jackets may also be equipped with ventilation openings. While all of these products provide shelter from wind and rain, they mainly differ in their ability to transport water vapor from within the clothing system to the outside. Various wearing studies have shown that, as compared to non-WVP constructions, both WVP membranes (3–5) as well as ventilation openings (6) help reduce moisture accumulations in the clothing system which are caused by augmented sweat rate during exercise in various conditions. This effect improves wearing comfort, as it leads to a dryer skin, which is less sensitive for temperature differences and skin-textile friction (7–11). In addition to its influence on wearing comfort, differences in vapor permeability and ventilation design may also affect measures that are relevant for physical performance and reflect the degree of effort: In warm environments, wearing-studies have demonstrated that usage of WVP protective clothing is associated with a slower rise in core temperature and lower energy consumption during exercise as compared to impermeable clothing systems (5,6,12,13). With regards to hiking, these findings have limited applicability as jackets mostly serve to keep the body warm in cold environments. Here, it is paramount to avoid moisture accumulations in the clothing system since wet cloth-

99

ing features increased heat capacity and thermal conductivity (14,15), resulting in a greater loss of body heat. In cold and windy conditions, this can lead to a higher energy consumption, cold stress and ultimately hypothermia, imposing serious health risks for hikers (16–19). In confirmation of this notion, Weller and Millard (20) found energy consumption, heart rate and levels of stress hormones to be higher when low-intensity exercise in a cold environment was performed in wet as compared to dry clothing. Clothing properties also influence the amount of sweat produced during exercise (21). Reduced sweat perspiration could help to delay the onset of dehydration, an essential risk especially during longer hikes (22,23). Yoo and Kim (24) found that higher water vapor permeability was associated with reduced loss of body weight due to sweating while exercising in cold conditions wearing cold protective gear. Similar observations were made for ventilation openings, which equally help to reduce sweat loss during exercise (25). However, it should be noted that both Ruckman et al. (25) and Yoo and Kim (24) used short-term (20 minutes or shorter), low-intensity exercise interventions, which do not reflect the physical demands of outdoor hiking (26). Additionally, it is unlikely that sweat production reaches a steady state after 20 minutes or less, so these findings may have limited generalizability (27). To date, no wearing studies have investigated the effect of different WVP jackets and ventilation openings on parameters reflecting physical effort under environmental and exercise conditions that are applicable to leisure hiking. Also, wearing studies have typically used tailor-made apparel prototypes to test the effects of WVP constructions and ventilation openings (3–5,24,25). It is important to note that both microclimate and wearing comfort do not only depend on a jacket’s membrane but are rather influenced by the concomitant influence of various factors, including garment design, cut and fit (28). Hence, it is unclear whether results obtained with custom-made prototypes can be extrapolated to commercially available jackets. The goal of this practice-oriented study was to investigate whether commercially available hiking jackets, differing in both price and textile features, would have a significant impact on moisture management and parameters reflecting physical effort. We aimed to use a setting of exercise and environmental conditions that is representative for hiking at a leisure level. The jackets tested were chosen to reflect the available product range from a basic, non-WVP jacket to a high-end jacket equipped with a PTFE membrane and ventilation openings. We hypothesized that jackets featuring water vapor permeable membranes and ventilation openings would benefit water transport from the skin to the outside

100

of the jacket, limit subjects’ weight loss due to sweating and minimize fluctuations in body temperature during exercise and subsequent rest.

METHODS

Subjects

Ten healthy and well trained male volunteers participated in the study (age: 27.1 ± 2.3 years, weight: 73.0 ± 6.0 kg, height: 176.2 ± 3.4 cm, BMI: 23.5 ± 1.4, self-reported sports activity level: 6.7 ± 2.4 hours/week). The study protocol was approved by the Board for Ethical Questions in Science of the University of Innsbruck (37/2015). Participants were informed about the study purpose and methods involved before giving written consent. Physical readiness to participate was assessed through completion of the Physical Activity Readiness Questionnaire (PARQ) (29).

Outdoor apparel

The jackets tested in this study were purchased on the market (size: M was found to fit all subjects included) and selected to reflect the quality range of products hikers may choose from when buying a wind- and waterproof jacket: A two-layer jacket equipped with a polyurethane membrane (Power Tex®; PM) and a three layer jacket with a stretched PTFE (Gore-Tex®) membrane were chosen. The latter jacket additionally featured ventilation openings in the armpit (length: 35 cm; no mesh lining) and was used twice: once with closed (PTC) and once with opened (PTO) ventilation openings. As an example of a nonsports specific alternative, a water vapor impermeable polyester jacket with polyurethane coating (Norway Protection®; PU) was also tested. All jackets were tested for wind- and waterproofness according to EN-ISO 9237:1995 and BS 3424-26:1990 standards and seams were also checked for waterproofness at the textile laboratory of the University of Innsbruck. Resistance to evaporative heat transfer (Ret) and resistance to conductive heat transfer (Rct) of the jackets were measured on a hot plate according to EN-ISO – 11092:2014: All jackets featured front zips, which were completely closed during the tests, and sleeve cuffs equipped with Velcro straps that were tightened during the tests. Further specifics and dimensions of the jackets are evident from table 1 and figure 1 shows a demonstrative picture of one subject wearing the jackets.

101

Tab. 1: Specifics and dimensions of test jackets

Manufacturer

Material

PTC/PTO

Mountain Equipment 100% polyamide

Membrane (brand name) Ventilation openings Air permeability (mm/s) Rct (m²K/W) Ret (m²Pa/W) Thickness (mm) Jacket length (cm) Waist size (cm) Sleeve length (cm) Weight (g) Retail price (Euro) GORE-TEX®

no/yes 1.726 ± 0.014 0.054 ± 0.010 6.552 ± 2.523 0.259 ± 0.008 74 108 62 521 499

PM

Salewa

100% polyester

Power Tex®

no 0.700 ± 0.006 0.050 ± 0.018 42.690 ± 5.275 0.126 ± 0.004 73 104 59 261 99

PU

Norway Protection 100% polyester with polyurethane coating none

no 0.000 ± 0.000 0.044 ± 0.000 199.621 ± 60.774 0.453 ± 0.004 78 112 56 565 20

Rct: Resistance to conductive heat transfer and Ret: Resistance to evaporative heat transfer.

102

Fig. 1: Subject wearing perwmeable jackets featuring a stretched PTFE (PTC/PTO; left) or polyurethane membrane (PM; middle) as well as an impermeable jacket with polyurethane coating (PU; right)

For execution of the tests, participants were provided with identical long-sleeve base layers (Ortovox, Taufkirchen, Germany; 80% merino wool, 17% polyamide, 3% spandex), soft shell hiking pants (Ortovox; Face: 74% polyamide, 6% spandex, 20% merino wool; Lining: 52% merino wool, 48% polyester) and a bandana used to cover the head (Buff S.A., Barcelona, Spain: 100% polyester). Additionally, subjects were wearing their individual socks, running shoes and boxer shorts and a 5 kg hiking backpack (Deuter Sport GmbH, Gersthofen, Germany).

Exercise intervention

The jackets were tested during a simulated hike that consisted of two phases: First, participants walked on a treadmill (pulsar, h/p/cosmos, Nussdorf-Traunstein, Germany) at a speed of 3.5 km/h and 15% inclination for one hour. Afterwards they were instructed to rest on a chair for 15 min to simulate a hiking break. Tests with the PTO jacket were performed such that ventilation openings were kept open during the walking phase and closed for the break to facilitate moisture transfer during activity and protect the subject during rest from excessive heat loss. All tests were performed in a climatic chamber (Kältepol, Natters, Austria) used in previous studies (17,30) under standardized environmental conditions (12 ± 1 °C, 40 ± 3% relative humidity). These conditions were chosen because 12°C represents the average daily mean temperature in St. Anton am Arlberg at an altitude of 1284 m in the period from May to September (i.e., the hiking season) (31). A wind machine (TTW 25000 S, Trotec, Heinsberg, Germany), positioned next to the treadmill at a 45° angle and facing the subjects, was used to simulate light wind (10 km/h) during the walking phase. During the 1-hour treadmill hike, a difference in altitude of 525 m was covered. According to ACSM guidelines, this activity coincides with an average oxygen uptake of 26.8 ml/(min*kg) and a metabolic heat production of 440 W/m2 and can, therefore, be considered a moderately intense exercise for healthy, young and physically active subjects (32). Subjects performed the protocol four times, always at the same time of the day, to test each jacket once in a randomized order. A minimum resting time of 24 h was granted between tests with different jackets. Subjects were advised to refrain from drinking coffee or alcohol on the testing day (33) and requested not to participate in sport activity 24 h before the testing. To ensure consistent hydration status, participants were asked to drink 500 ml of water one hour before and to empty their bladder immediately before testing (34).

103

Measurements

Temperature and relative humidity were continuously recorded. Further measurements were obtained at five points of time: Before the walking phase (t0), after 20 min (t1), 40 min (t2) and 60 min (t3) of walking, and at the end of the cool down phase (t4). Measures of tympanic temperature and heart rate were obtained at all points of time. Humidity of the stratum corneum was measured at t0, t3 and t4. Weight measurements were conducted at t0 and t4 only.

Moisture management

To evaluate moisture management, three parameters were measured: (i) microclimate, (ii) humidity of the stratum corneum and (iii) sweat residues in the clothing system. To obtain data reflecting the microclimate between skin and base layer as well as that between base layer and outer jacket, sensors (SHT 15-sensors, Sensirion AG, Stafa, Switzerland) measuring temperature and relative humidity were attached to the skin and base layers using adhesive tape (care was taken not to cover sensitive areas). Sensors featured filter caps for protection against dripping sweat. The exact measurement positions were on the chest in the middle of the sternum as well as 5 cm below the armpit; these regions are known for high levels of sweat production (35). Data were continuously recorded using data loggers (sampling frequency: 0.17 Hz). As, during test execution, the measures obtained on the chest and below the armpit showed congruent changes over time, the average of these two values was calculated for further analysis. Humidity of the stratum corneum was measured in the umbilical and lumbar region (CM 825 Corneometer, CK electronic GmbH, Cologne, Germany). For consistency, measurement areas were marked with a waterproof pen. For each measurement, the average of three measures was calculated and the mean of the two regions was used for further analysis (similar changes over time). Results are presented in arbitrary units ranging from 0 (dry) to 120 (on water) (36). Jackets and the remaining clothing (bandana, hiking pant, and base layer) were separately weighted using a high-precision scale (Kern DS 150K1, Kern & Sohn GmbH, Balingen-Frommern, Germany; readout precision: 1 g) to determine sweat residues.

Measures of physical effort

Tympanic temperature, heart rate and weight loss of the subjects were measured as indicators of the degree of physical effort. Tympanic temperature was measured in the left ear using a thermometer, which was kept under constant conditions (20 °C) between measurements (ThermoScan IRT 4520, Braun,

104

Germany). During the protocol, the ears were covered with a bandana to prevent potential bias resulting from cooling of the outer auditory canal. Heart rate was measured via chest belt (Polar Electro Oy, Kempele, Finland). To estimate the loss of water due to sweating and respiration, the subjects were weighted in underwear (Kern DS 150K1, Kern & Sohn GmbH, Balingen-Frommern, Germany) and the average of five consecutive measurements was considered for further analyses (37).

STATISTICAL ANALYSES

Factorial ANOVAs with repeated measurements were used to determine the influence of the factors “jacket” and “time” on tympanic temperature, relative humidity and heart rate as well as subjective perceptions of scratching, thermal comfort and exertion. Differences in the weight of subjects and clothing between t0 and t4 were calculated and compared between jackets by one-way ANOVAs. In cases where Mauchly’s test indicated a violation of the assumption of sphericity, degrees of freedom were corrected by the Greenhouse-Geisser procedure. For the main factor “jacket”, Sidak-adjusted post hoc tests were used to follow up significant ANOVA results. Values are reported as mean values ± standard deviation (SD). Differences were considered significant at p ≤ 0.05. SPSS Statistics Version 21 (IBM, Armonk, USA) was used for all statistical calculations.

RESULTS

Moisture management

The values of relative humidity measured between skin and base layer are evident from figure 2(a). Relative humidity increased steadily from t0 (45 ± 2.7%) to reach a maximum at t3 (73.1 ± 4.8%) and dropped only slightly during cool down (t4: 72.7 ± 6.5%). The effect of “time” was found to be significant (F(1.134, 10.202) = 63.506, p < 0.001). Across measuring times, ANOVA also revealed a significant effect for “jackets” (F(3, 27) = 5.416, p = 0.005). As compared to PU, relative humidity was significantly lower when using PTC (p = 0.006) and a tendency towards lower relative humidity was observed for PTO (p = 0.125). “Jacket × time” interactions showed no significant difference (F(3.968, 35.715) = 2.561, p = 0.198).

105

Figure 2(b) shows the values of relative humidity as measured on the chest and below the armpit between base layer and jacket. Across jackets, relative humidity was constantly rising by 33% from t0 (49.0 ± 4.6%) to cool down (t4: 73 ± 9.8%). This is reflected by a significant effect of the factor “time” (F(1.481, 13.333) = 61.152, p < 0.001). ANOVA also indicated significant differences between jackets (F(3, 27), p < 0.001). Post hoc t-tests demonstrated that relative humidity between base layer and jacket was lowest in PTO, followed by PTC, PM and PU, with differences being significant between products: PTO vs. PM (p = 0.004), PTO vs. PU (p < 0.000), PTC vs. PM (p = 0.003) and PTC vs. PU (p < 0.000). ANOVA showed significant “jacket × time” interaction-effects (F(4.093, 36.836) = 4.723, p = 0.003) indicating a slower rise in relative humidity for PTO compared to the other jackets.

Fig. 2: Relative humidity between skin and base layer (a) and between base layer and jacket (b) at the beginning of the protocol (t0), during the walking phase (t1-t3) and after cool down (t4). Error bars are deliberately omitted for improved clarity

During the exercise intervention, humidity of the stratum corneum was rising with all jackets, as compared to the starting point. On average, values increased from 46.4 ± 11.0 (t0) to 96.1 ± 27.3 (t3) during walking and dropped to 66.7 ± 18.2 during cool down (t4). ANOVA revealed a statistical effect for the factor “time” (F(1.271, 11.437) = 71.316), p < 0.001). Comparisons of jackets showed that, across all measuring points, the humidity of the stratum corneum was highest with PM (71.9 ± 26.4), followed by PU (71.8 ± 27.0) and PTC (69.5 ± 26.7). The lowest average stratum corneum humidity was measured with the PTO jacket (65.5 ± 23.1). However, differences between jackets were not statistically significant (F(3, 27) = 0.987, p = 0.414). The “jacket × time” interaction effect, by contrast, just failed to reach statistical significance (F(2.814, 25.323) = 2.532, p = 0.083), which hints to a slower rise in the humidity of the stratum

106

corneum during the protocol with PTO as compared to PTC, PM and PU. All values for the humidity of the stratum corneum are evident from table 2.

Tab. 2: Humidity of stratum corneum

Time PTO PTC PM PU

t0 (0 min) 47.0 ± 10.5 48.3 ± 13.1 47.3 ± 9.2 42.7 ± 7.8 t3 (60 min walking) 88.0 ± 22.0 97.8 ± 21.0 99.7 ± 19.4 98.8 ± 15.6 t4 (15 min cool down) 61.7 ± 13.2 62.4 ± 18.1 68.7 ± 15.3 73.8 ± 16.9 Note: Data are given in arbitrary units ranging from 0 (dry) to 120 (on water).

The weight gain of jackets and the remaining apparel (base layer, hiking-pants and bandana) from t0 to t4 are shown in figure 3(a) and (b). Only the PU jacket evidenced a substantial gain in weight during the protocol (43.3 ± 16.3 g). Accordingly, ANOVA (F(1.038, 9.345) = 81.230, p < 0.001) and associated post hoc tests reflected significant differences in weight gain between the PU jacket and all further models (p < 0.001 for all comparisons). Also, the remaining apparel was found to be heavier at t4 as compared to t0. Here, ANOVA results demonstrated that the weight gain differed significantly in dependency of the jacket used (F(1.665, 14.981) = 20.050, p < 0.001). It was most pronounced

107

Fig. 3: Weight gain of jackets (a) and the remaining apparel (b) as measured between t0 and t4. Fig. 3 (c) shows the concomitant weight loss of subjects

Fig. 4: Heart rate (a) and tympanic temperature (b) at the beginning of the protocol (t0), during the walking phase (t1-t3) and after cool down (t4). The right-most columns show the average as measured during the whole protocol

108

with PU (33.7 ± 23.5 g), followed by PM (11.6 ± 14.1 g) and PTC (2.4 ± 7.6 g). No notable weight gain was observed with PTO (–0.1 ± 8.6 g). Significant post hoc pairwise comparisons are evident from figure 3(a) and (b).

Physical effort

The participants lost on average 386 ± 88 g in weight during the simulated hike, which coincides with a loss of 0.5 ± 0.1% of body weight (figure 3(c)). Differences in weight loss between jackets were not significant (F(1.598, 14.383) = 1.049, p = 0.360). Across all jackets, heart rate as shown in figure 4(a) increased from 64.7 ± 9.9 bpm at t0 to 116.2 ± 11.7 bpm (+43%) at the end of the walking phase (t3), and returned to baseline measures during cooldown (t4: 66.1 ± 9.4 bpm). Accordingly, ANOVA revealed a significant effect of “time” (F(1.919, 17.276) = 259.887, p < 0.001). Across all measuring points, no significant differences were identified between jackets (F(3, 27) = 0.619, p = 0.609). Also no significant “jacket × time” interaction effects were found (F(4.667, 42.004) = 1.011, p = 0.420). Mean tympanic temperature (figure 4(b)) increased at the beginning of the exercise (t0: 36.7± 0.5 °C; t1: 37.0 ± 0.6 °C) but then returned again to baseline values during the intervention. Even though changes in tympanic temperature were small, the factor “time” had a statistically significant effect on tympanic temperature (F(2.395, 21.557) = 3.471, p = 0.042). No significant differences in tympanic temperature were found between jackets (F(3, 27) = 0.639, p = 0.597). ANOVA showed no significant “jacket × time” interaction effects (F(3.610, 32.486) = 0.765, p = 0.544).

109

DISCUSSION

The aim of this study was to investigate whether commercially available hiking jackets, differing in both price and textile features, would have a significant impact on moisture management and the actual degree of physical effort during a simulated hike under controlled environmental conditions. In agreement with our hypothesis, our results showed that jackets featuring water WVP membranes and ventilation openings facilitate water transport from the skin to the outside, resulting in lower relative humidity in the clothing system and associated weight gains of jackets and remaining apparel. However, we found that water transport capacity had no significant effect on overall sweat loss, heart frequency or tympanic temperature, suggesting that improved moisture management does not significantly affect parameters reflecting the actual degree of physical effort during hiking. To evaluate moisture management, we measured relative humidity underneath the jacket, humidity of the stratum corneum and weight gain in the clothing systems. All measurements consistently showed that humidity was always lowest for PTO followed by PTC and PM, and highest for PU. Also, sweat residues in the clothing system and weight gains of the jacket were largest for PU and smallest for PTO. This can be explained by the different water vapor permeability properties of the jackets and the presence/absence of ventilation openings: PU is impermeable to water vapor which leads to larger amounts of humidity getting trapped beneath the jacket (14,38). PTC/PTO feature a considerably lower Ret (6.6 ± 2.5 m²Pa/W) in comparison to PM (42.7 ± 5.3 m²Pa/W) which enables higher sweat-evaporation through the jacket (3,39) and leads to lower levels of relative humidity beneath the jacket and on the skin during and after exercise. PTO in comparison to PTC only differs in the presence of ventilation openings which can further reduce humidity in the clothing system (6). During the entire intervention (t0 – t4), the increase in relative humidity between jacket and base layer was 9.5% greater for PTC than for PTO and average values for relative humidity (t0 – cool down) were consistently lower for PTO in comparison to PTC. Only PTO showed no average weight gain in the whole clothing system. Ultimately, greater humidity within the clothing system may also increase skin moistness. While large standard deviations precluded results from reaching statistical significance, our measurements indicated that stratum corneum humidity increased at a slower rate and by a smaller degree with PTO as compared to other jackets (10–16% differences to other jackets). This may be im-

110

portant for wearing comfort, as wetter skin is known to be more sensitive for temperature differences and skin-textile friction (7,8–11). Indeed, questionnaire-based assessments showed that the subjective perception of scratching (data not reported) was greatest with PU, which also showed the highest values for absolute humidity between skin and base layer. Generally, however, we found stratum corneum humidity values to be low, which may be due to the standardized base layers made of 80% merino wool. This material is known for its good wicking and absorption abilities that may have prevented excessive skin wetting during the protocol (30). The advantages of WVP clothing systems and ventilation openings have also been demonstrated in earlier studies performed with tailor-made apparel prototypes (3–6). It is important to note that, as opposed to such prototypes, commercially available outdoor jackets are not only distinguished by membrane permeability and the existence (or lack of) ventilation openings but may also differ in cut and other design features. Indeed, the jackets used in this study slightly differed in size, with PU (the largest jacket in the test) being 6 cm longer and 7% larger around the waist as compared to PM (the smallest jacket). A looser fit creates larger air gaps between body and jacket which, in combination with the body movement during walking, lead to greater chimney and bellows effects (40–42). These effects favor increased air exchange between the in- and outside of the clothing system, thereby benefitting reduction of moisture. However, the humidity measurements performed in our study suggest an overwhelming influence of membrane permeability and ventilation openings. For end consumers it is therefore important to recognize that, possible differences in cut notwithstanding, (i) the membrane’s Ret is a useful indicator of a jacket’s capacity to dissipate water vapor and (ii) only jackets featuring a highly WVP membrane characterized by a low Ret in combination with ventilation openings can keep jacket and base layer dry during leisure hiking. We hypothesized that the disparities in the microclimate would be reflected by differences in the physiological reactions to the simulated hike. Specifically, we anticipated that during exercise the body would react to the greater relative humidity beneath less permeable jacket with a more pronounced rise in tympanic temperature which was assessed as substitute measure for core temperature (17). This is because at high relative humidity, the ability to dissipate heat through evaporation of sweat is impaired (43). We further expected the rise in tympanic temperature to be accompanied by an increase in heart rate since the human body aims to increase blood flow to the periphery in order to dissipate excess heat (44,45). Ultimately, a steeper rise in core temperature during walk-

111

ing would also result in greater sweat rates reflected by a larger loss of body weight with less WVP jackets. In conflict with these hypotheses and earlier studies that reported a significantly lower loss in body weight for more WVP clothing (24,25), no significant differences in tympanic temperature, heart rate or weight loss were found between jackets. One difference between our and the aforementioned studies lies in exercise duration: The exercise bouts used by Yoo and Kim (24) and Ruckman et al. (25) may have been too short (20 minutes or less) to obtain reliable results. This is because longer exercise durations are required for a steady state in physiological reactions to be reached (27). In support of this assumption and our results, Kuklane et al. (4) reported similar sweat rates for both permeable and impermeable clothing during 60-minute low-intensity exercise in the cold. Further, it may be speculated that the influence of jackets on the physiological parameters measured would be more pronounced if the exercise was performed at greater intensity and under warmer environmental conditions. However, moderate exercise intensity and modest climatic conditions were deliberately chosen in our study as they are representative for leisure hiking. Conversely, we assumed that impermeable jackets would provide less protection against heat loss during the rest period following the hiking intervention, since wet clothing features increased heat capacity and thermal conductivity (14,15). The anticipated greater loss of body heat was expected to be reflected by a steeper decrease in tympanic temperature but no such decrease was found. The relatively moderate exercise intensity and the temperate climatic conditions chosen might also explain this rather counterintuitive observation. Possibly, WVP clothing systems would only provide a significant physiological advantage over non WVP-apparel during longer breaks after high-intensity exercise in colder environments (17,20,46).

CONCLUSIONS

Based on our findings, it can be concluded that high-quality hiking jackets featuring highly permeable membranes and ventilation openings benefit moisture management during leisure hiking at low to moderate exercise intensity under temperate climatic conditions. A drier microclimate is expected to favor wearing comfort. However, comparison with more favorably-priced, nonWVP products revealed that the choice of jacket does not significantly affect the physiological reactions to leisure hiking.

112

FUNDING STATEMENT

This work was carried out within the Competence Centre for Sports Textiles framework and supported by the Standortagentur Tirol and the Landesregierung Vorarlberg.

DECLARATION OF CONFLICT OF INTERESTS

The authors declare that there is no conflict of interests.

LITERATUR

(1)

(2)

(3)

(4)

(5)

(6)

(7)

(8)

(9) Menzel A., Dreyer A., Ratz J. Trekking Tourism as a Special Form of Hiking Tourism-Classification and Product Design of Tour Operators in the German-speaking market. J Tour 2012; 13(2): 23–46. Muhar A., Schauppenlehner T., Brandenburg C., Arnberger A. Alpine summer tourism: the mountaineers’ perspective and consequences for tourism strategies in Austria. For Snow Land Res 2007; 81(1/2): 7–17. Bartels V., Umbach K.H. Water vapor transport through protective textiles at low temperatures. Res J 2002; 72(10): 899–905. Kuklane K., Gao C., Holmér I., Bröde P., Candas. Physiological responses at 10 and 25 C in wet and dry underwear in permeable and impermeable coveralls. in The 12th International Conference on Environmental Ergonomics. 2007; Coimbra, Portugal: Biomed. Guo Y., Li Y., Tokura H., Wong T., Chung J. Impact of fabric moisture transport properties on physiological responses when wearing protective clothing. Res J 2008; 78(12): 1057–1069. McQuerry M., Den Hartog E., Barker R., Ross K. A review of garment ventilation strategies for structural firefighter protective clothing. Res J 2016; 86(7): 727–742. Chen Y., Fan J., Zhang W. Clothing thermal insulation during sweating. Res J; 2003. 73(2): 152–157. Fukazawa T., Havenith G. Differences in comfort perception in relation to local and whole body skin wettedness. Eur J Appl Physiol 2009; 106(1): 15–24. Gerhardt L.-C., Strässle V., Lenz A., Spencer N., Derler S. Influence of epidermal hydration on the friction of human skin against textiles. J R Soc Interface 2008; 5(28): 1317–1328.

113

(10) Havenith G. Interaction of clothing and thermoregulation. Exog Derm 2002; 1(5): 221–230. (11) Fan J., Tsang H.W. Effect of clothing thermal properties on the thermal comfort sensation during active sports. Res J 2008; 78(2): 111–118. (12) Dorman L.E., Havenith G. The effects of protective clothing on energy consumption during different activities. Eur J Appl Physiol 2009; 105(3): 463–470. (13) Sato M., Nakagawa M., Tokura H., Zhang P., Gong R.,Physiological effects of outerwear moisture transfer rate during intermittent bicycle exercise. J Text I 2007; 98(1): 73–79. (14) Voelker C., Hoffmann S., Kornadt O., Arens E., Zhang H. Heat and moisture transfer through clothing, in Eleventh international IBPSA conference. 2009;UC Berkeley:

Center for the Built Environment: Glasgow, Scottland. (15) Meinander H., Hellsten M. The influence of sweating on the heat transmission properties of cold protective clothing studied with a sweating thermal manikin. Int J Occup

Saf Ergon 2004; 10(3): 263–269. (16) Armstrong L.E., Epstein Y., Greenleaf J.E., Haymes E.M., Hubbard R.W. Heat and cold illnesses during distance running. Med Sci Sports Exerc 1996; 28(12): 377–390. (17) Burtscher,M., Kofler P., Gatterer H., Faulhaber M., Philippe M. Effects of lightweight outdoor clothing on the prevention of hypothermia during low-intensity exercise in the cold. Clin J Sport Med 2012; 22(6): 505–507. (18) Young,A.J., Castellani J.W., Exertional fatigue and cold exposure: mechanisms of hiker’s hypothermia. Appl Physiol Nutr Metab 2007; 32(4): 793–798. (19) Noakes T.D. Exercise and the cold. Ergonomics 2000; 43(10): 1461–1479. (20) Weller A., Millard C., Stroud M., Greenhaff P., Macdonald I. Physiological responses to cold stress during prolonged intermittent low-and high-intensity walking. Am J

Physiol Regul Integr Comp Physiol 1997; 272(6): 2025–2033. (21) Gonzalez R.R., Cheuvront S.N., Montain S.J., Goodman D.A., Blanchard L.A., Expanded prediction equations of human sweat loss and water needs. J Appl Physiol 2009; 107(2): 379–388. (22) Cheuvront S.N., Kenefick R.W. Dehydration: physiology, assessment, and performance effects. Compr Phys 2014; 4(1): 257–285. (23) Boulware D.R., Forgey W.W., Martin W.J. Medical risks of wilderness hiking. Am J

Med 2003; 114(4): 288–293. (24) Yoo S., Kim E. Wear trial assessment of layer structure effects on vapor permeability and condensation in a cold weather clothing ensemble. Res J,2012; 82(11): 1079–1091. (25) Ruckman J., Murray R., Choi H. Engineering of clothing systems for improved thermophysiological comfort: the effect of openings. Int J Clo Sci Tech 1999; 11(1): 37–52.

114

(26) Burtscher M. Endurance performance of the elderly mountaineer: requirements, limitations, testing, and training. Wien Klin Wochenschr,2004; 116(21–22): 703–714. (27) Holmér I. Human wear trials for cold weather protective clothing systems, in Textiles for Cold Weather Apparel, J. Williams, Editor. 2009, Woodhead Publishing in Textiles:

Cambridge. 256–273. (28) Bishop P., Balilonis G., Davis J.K., Zhang Y. Ergonomics and comfort in protective and sport clothing: a brief review. Journal of Ergonomics 2013; S2:005, doi: 10.4172/2165–7556.S2-005. (29) Adams R., Revised Physical Activity Readiness Questionnaire. Can Fam Physician 1999; 45: 992. (30) Kofler P., Nussbichler M., Veider V., Khanna I., Heinrich D. Effects of two different battings (sheep wool versus polyester microfiber) in an outdoor jacket on the heat and moisture management and comfort sensation in the cold. Res J 2015; 86(2): 191–201. (31) Zentralanstalt für Meterologie und Geodynamik (ZAMG), Klimadaten von Österreich 1981–2010. 2016. (32) American College of Sports Medicine, ACSM’s guidelines for exercise testing and prescription. 2013, Philadelphia: Lippincott Williams & Wilkins. (33) Del Coso J., Estevez E., Mora-Rodriguez R. Caffeine during exercise in the heat: thermoregulation and fluid-electrolyte balance. Med Sci Sports Exerc 2009; 41(1): 164–173. (34) Mora-Rodríguez R., Fernández-Elías V.E., Hamouti N., Ortega J.F. Skeletal muscle water and electrolytes following prolonged dehydrating exercise. Scand J Med Sci Sports 2015; 25(3): 274–282. (35) Smith C.J., Havenith G. Body Mapping of Sweating Patterns in Athletes: A Sex Comparison. Med Sci Sports Exerc 2012; 44(12): 2350–2361. (36) Heinrich U., Koop U., Leneveu‐Duchemin M.C., Osterrieder K., Bielfeldt S. Multicentre comparison of skin hydration in terms of physical‐, physiological‐and product‐dependent parameters by the capacitive method (Corneometer CM 825). Int J Cosmet

Sc 2003; 25(1–2): 45–53. (37) Agache P.G., Agache P., Humbert P. Measuring the skin. 2004, Luxemburg: Springer

Science & Business Media. (38) Li Y. The science of clothing comfort. Prog 2001; 31(1–2): 1–135. (39) Bartels V. Physiological comfort of sportswear, in Textiles in sport, R. Shishoo, Editor. 2005, Woodhead Publishing: Cambridge. 177–203. (40) Gavin T.P. Clothing and thermoregulation during exercise. Sports Med 2003; 33(13): 941–947.

115

(41) Weder M., Zimmerli T., Rossi R. A sweating and moving arm for the measurement of thermal insulation and water vapour resistance of clothing, in Performance of Protective Clothing: Fifth Volume, S. Johnson and S. Mansdorf, Editors. 1996, ASTM International: Pennsylvania. 257–269. (42) Zhang X., Li J., Wang Y. Effects of clothing ventilation openings on thermoregulatory responses during exercise. Indian J Fibre 2012; 37(2): 162–171. (43) Plowman S.A., Smith D.L. Exercise physiology for health fitness and performance. 2013, Philadelphia: Lippincott Williams & Wilkins. (44) Keytel L., Goedecke J., Noakes T., Hiiloskorpi H., Laukkanen R. Prediction of energy expenditure from heart rate monitoring during submaximal exercise. J Sports Sci 2005; 23(3): 289–297. (45) Turner J.R. Cardiovascular Reactivity and Stress. 2014, Berlin: Springer. (46) Daanen H. Physiological strain and comfort in sports clothing, in Textiles for Sportswear, R. Shishoo, Editor. 2015, Woodhead Publishing in Textiles: Cambridge. 153–168.

116