Effects of clothing ventilation openings on thermoregulatory responses during exercise

Indian Journal of Fibre & Textile Research Vol. 37, June 2012, pp. 162-171 Effects of clothing ventilation openings on thermoregulatory respoes during exercise X H Zhang, J Li a & Y Y Wang Fashion & Art Design Ititute, Donghua University, Shanghai 200051, P R China Received 20 March 2011; revised received and accepted 10 May 2011 The effect of clothing openings on thermoregulatory respoes of wearers during a treadmill exercise in controlled laboratory conditio has been studied. Nine short sleeved T-shirts with varying design of clothing openings at neck and hem have been designed, and the test is performed on six males, coidering 10min of standing rest, 30min of running at 55% of VO 2max followed by 10min of rest. Heart rate, rectal temperature (T re ), skin temperatures (T sk ), clothing microclimate temperature (T cl ) and relative humidity (RH cl ) have been studied and the subjective ratings on thermal, sweating and comfort seatio are collected. The results show significant differences in mean values of skin T sk, T cl and RH cl among the clothing with different sizes of neck openings. There are no significant differences between clothing with moderate and loose hem opening. Heat storage during exercise and recovery periods shows significant relatio with the ventilation area of clothing neck opening. It appears that the neck opening plays a more significant role to improve heat trafer during exercise than the hem opening. Hence, varying design of clothing openings could affect thermophysiological comfort of wearers; the T-shirt with loose neck opening and moderate hem opening is the best one in releasing heat from the body. Keywords: Clothing openings, Heat storage, Microclimate, T-shirt, Thermoregulatory respoe, Ventilation area 1 Introduction An important aspect of thermal comfort in clothing is the possibility to dissipate heat by evaporating sweat 1. However, when clothing is worn, the latent heat flux created by evaporating sweat can t be efficiently tramitted through clothing and released to the outer environment, hence the relative humidity of the microclimate increases and heat dissipation is reduced, which can lead to discomfort 2. Since clothing can be a potential obstacle to the heat and moisture trafer, it is important to examine the methods for reduction of thermal stress on wearers 3-5. A more suitable way of alleviating heat strain caused by heat build up in the microclimate may be to increase the rate of air exchange between the clothing and the environment 6,7. When air enters an eemble, a mount of heat will be traported away from the wearer, with possible physiological coequences. Birnbaum et al. 6 suggested that in a cool environment a 100l min -1 through-flow of air could remove 27.39W m -2 of heat because of the increased convective and evaporative heat trafer it causes. Hence, the exchange of air between the clothing a To whom all the correspondence should be addressed. E-mail: lijun@dhu.edu.cn microclimate and the external environment, i.e. clothing ventilation, is an important determinant of thermal comfort. The rate of microclimate air exchange depends on air permeability of the fabric, presence of openings, wind speed, body movements, and other factors 6,7. Coidering these factors, it can be assumed that the design of clothing will also influence the traportation of sweat from the body. A number of studies have been conducted on the air permeability of the fabrics upon physiological, thermoregulatory, or comfort seation respoes of wearers during exercise 2,8-13. Many modern waterproof breathable fabrics or absorption & quick drying fabrics have been introduced to the market, which claimed to improve evaporative characteristics and provide maximum thermophysiological comfort for wearers 14. In addition to coidering the properties of clothing fabric, the use of the most suitable desig on the clothing is also a key to optimize the thermal comfort of the wearer 1,15. For example, mesh fabrics applied at two vertical sides of the body trunk in sportswear is the best choice, because its open cotruction is believed to be highly beneficial for releasing heat and moisture away from the body 5,16. Pit zips, which appeared underneath the armpit, are featured on jackets allowing the upper arm to be fully

ZHANG et al.: EFFECTS OF CLOTHING VENTILATION OPENINGS ON THERMOREGULATORY RESPONSES 163 ventilated 15. Studies have shown that if an individual begi to feel warm, then the neck area should be uncovered or enlarged first for providing a vent to allow the chimney effect to be induced 17. Reischl et al. 18,19 developed a new designed firefighter s protective clothing by enlarging the neck opening 40% larger than the standard turn-out coat and the testing results indicated that skin temperature was significantly influenced by garment desig. It should be noted that among all sorts of ventilation features provided within a clothing system, the clothing natural openings, i.e. the neck opening and the hem opening, are the most basic way for air exchange between the clothing microclimate and the environment. However, little work has been done in the past on exactly how effective the clothing openings are and how the exact sizes of the openings and their combinatio impact the human thermoregulation respoes during body movements. In this study, a series of T-shirts with different sizes of clothing openings at neck and hem were designed and tested so as to investigate the effects of clothing openings on subjects physiological and subjective respoes under the condition of exercising on a treadmill in a moderate environment. Therefore, it is an advantage to the designer to be able to determine the effects of clothing openings on reducing physiological strain and develop garments that can enhance thermoregulation in total clothing system. 2 Materials and Methods 2.1 Subjects Eight young male volunteers participated in this study. All subjects were physically active in leisure activities and nomoking, with no underlying problems. All details of the study, the purpose and medical risks were fully explained, and informed written coent was given by all subjects. The physical characteristics of the subjects are as follows (mean±sd): age 23.5±1.5 years, weight 63.5±6.5kg, height 172±2cm, body surface area 20 1.75±0.09m 2. The maximal oxygen uptake (VO 2max ) was predicted from the time taken to run 2km a few days before the beginning of the experiment 21. The average VO 2max of the subjects was 51.0±1.5mL min -1 kg -1. The subjects were asked to refrain from caffeinated beverage for 2h prior to each experiment, and each subject performed at the same time of day to control for circadian fluctuation in body temperature 22. 2.2 Clothing A crew neck and short raglan sleeve basic T-shirt was chosen for control sample as it represents the garment most typically worn during training or recreational exercise. The standard T-shirt served as the platform for the development of other T-shirts. The size specificatio for the control sample (I0) are shown in Table 1. Eight T-shirts (I1-I8) with varying size of clothing opening at neck and hem were designed and produced for evaluation, i.e. (i) three design variatio (group1: I1-I3, group2: I0 and I4-I5, group3: I6-I8) of neck opening: tight, moderate and loose, and (ⅱ) three design variatio(group1: I1, I5 and I7, group 2: I0, I2 and I8, group3: I3, I4 and I6) of hem opening: tight, moderate and loose. The opening size of the control sample at neck or hem was regarded as the moderate opening style respectively. In order to standardize the desig for comparison, the torso and sleeve patter were drafted from the control sample to provide the basic blocks for other desig. All T-shirts were cotructed using the same basic sewing cotruction and 100% polyester interlock eyelet knit fabric (152g m -2 ), only the sizes of clothing openings were different. In the T-shirts with narrow opening at neck or hem, highly elastic tapes were italled at corresponding part so as to keep the openings tightly. In order to quantize the characteristic of clothing openings, the subjects were scanned in each T-shirt using a 3D whole body scanner ([TC] 2, USA) and software to determine the ventilation area of clothing opening at neck or hem. The ventilation area of clothing opening was determined by subtracting the area of the nude body from the area of the scan with T-shirt at corresponding part respectively. The size characteristics for all T-shirts are shown in Table 2. Each garment was washed once, and hung in an environmentally controlled chamber for a minimum of 24 h before any test. Table 1 Size specificatio of the control sample Sketch Measurement Size, cm A: Chest width 102 B: Hem opening 102 C: Neck opening 56 D: Sleeve opening 35 E: Back length 70 Control sample F: Sleeve length 40

164 INDIAN J. FIBRE TEXT. RES., JUNE 2012 Clothing Table 2 Details of T-shirts designed in experiments Size of neck opening, cm Size of hem opening, cm Ventilation area of neck opening, cm 2 Ventilation area of hem opening, cm 2 I0 (Control) 56 102 41.56±4.31 180.91±18.41 I1 Tight Tight 0.00±0.00 0.00±0.00 I2 Tight 102 0.00±0.00 180.91±18.41 I3 Tight 146 0.00±0.00 341.67±18.69 I4 56 146 41.56±4.31 341.67±18.69 I5 56 Tight 41.56±4.31 0.00±0.00 I6 78 146 169.06±7.70 341.67±18.69 I7 78 Tight 169.06±7.70 0.00±0.00 I8 78 102 169.06±7.70 180.91±18.41 2.3 Experimental Procedure and Measurement The experiment trials were performed in a chamber at cotant ambient temperature of 25±2 C, and relative humidity of 50±5% with an air velocity of around 0.2m s -1. This environment is representative of a common condition that could keep a resting man (producing heat at the rate of 60kcal h -1 m -2 ) feel comfortable when wearing tested garments (roughly 0.5clo) according to the Psychometrics Chart 23. The subjects initially rested in the chamber for about 10min to be adapted to the environment before the experiment started. All subjects were itructed to wear tested T-shirts next to the skin on upper body and the same underpants and shorts (both made of 100% cotton) on lower body. The same anklet socks and footwear were also used for all subjects on each occasion. The exercise protocol was coisted of 10min of standing rest, 30min of running on a treadmill (Model1000, Sports Art Ind., Co., Ltd) at 55% of VO 2max, and 10min of standing rest to recover. The test was conducted for 1h in total. The order of clothing testing sequence was randomly assigned to reduce the likelihood of any order effect. During exercise, heart rate (HR) was monitored using a polar heart rate monitor (t6c, SUNNTO, Finland) every 5min. Rectal temperature (T re ) was measured using a temperature seor (Model YSI- 401, yellow spring itruments; accuracy ±0.1 o C) that was ierted 10cm beyond the anal sphincter, and data were stored every 5min. Skin temperature (T sk ) was measured with surface thermometers (Model 285-661, RS Component Ltd; accuracy of ±0.1 o C) held in place with adhesive electrodes placed over the left side of the body at eight sites (forehead, scapula, chest, upper arm, lower arm, hand, thigh, and calf). Fig. 1 Subject rating scales for thermal seation, sweating seation and comfort Fig. 2 Experiment protocol and measurements items The microclimate temperature (T cl ) and relative humidity (RH cl ) were recorded by platinum resistance thermometer (Model 362-9834, RS Component Ltd; accuracy of ±0.1 C) and hygrothermometer (Model HIH4000-001, RS Component Ltd; accuracy of ±2%RH) respectively at chest level. All temperature and relative humidity measurements were automatically collected using a physiological data monitoring system every 30s. Nude body weights (m b ) were determined using an electronic counting platform scale (TCS-100Z, Yousheng Weighing Apparatus Co. Ltd., China; accuracy of ±10g) before and after the experiment. The mass of all tested clothing (m cl ) was also determined before and immediately after the experiment using a precision scales (LARK LP 502A, China; accuracy of ±0.01g) to quantify garment moisture retention during exercise. Subjective perceptio of thermal seation 24, sweating seation and comfort 25 were obtained by using three visual analog scales. The subjects were asked to point on the scales their subjective assessments before and after the experiment. The scales are shown in Fig. 1. The experiment protocol and measurements are shown in Fig. 2.

ZHANG et al.: EFFECTS OF CLOTHING VENTILATION OPENINGS ON THERMOREGULATORY RESPONSES 165 2.4 Calculation Mean skin temperature (T sk ) was calculated as an average of eight skin sites using the following equation 26 : sk hand ( T + T T ) T = 0. 05 T + 0. 07 + calf thigh forearm chest upperarm head 0. 20 T + 0. 19 T + 0. 175 T + 0. 175 T (1) back Mass of sweat evaporated (m sw ) from the subjects during exercise was calculated from the changes in nude body mass ( m b ) before and after the experiment, corrected for mass variatio of all tested garments ( m cl ) measured during the experiment. It is assumed that all non-evaporated sweat was absorbed by the clothing, since no dripping was observed. Sweat evaporation efficiency was calculated as the amount of sweat evaporated divided by total body mass loss. Body heat storage (S) during exercise and recovery periods was calculated respectively using the following equation 27 : - 0.965 mb Tb S (W m 2 ) = (2) A t D where 0.965 is the average specific heat of body tissues (W h -1 kg -1 ); m b, the body weight (mean of pre and post weights) (kg); A D, the body surface area (m 2 ); T b, the change in the mean body temperature and were estimated from measurements of T re and T sk (T b =0.9 T re +0.1T sk ) ( ) 27 ; and t, the time (h). 2.5 Statistical Analyses Changes in HR, T re, T sk, T cl and RH cl were examined by a two-way analysis variance (ANOVA) with repeated measures (Clothing Time). When this analysis revealed significant differences between sessio, a Tukey post-hoc test was used to compare the nine tested clothing. Analyses were performed for the data at time 0, 10, 40 and 50min respectively. The associated body mass loss, sweat loss, sweat efficiency, heat storage and subjective perceptio were tested by a one-way ANOVA. Statistical significance was set at p<0.05. Furthermore, Pearson correlation coefficients were calculated to investigate relation between heat storage and ventilation areas of clothing openings during exercise and recovery Table 3 Turkey tests for significant main effects of neck opening on physiological measure during exercise and recovery periods Variance Exercise period Recovery period Mean Grouping a Mean Grouping a HR (bpm) Tight 161.23±3.38 84.41±9.09 Moderate 162.00±5.36 86.09±5.41 Loose 158.20±3.29 84.30±8.59 T re ( ) Tight 37.50±0.21 37.24±0.21 Moderate 37.46±0.22 37.19±0.17 Loose 37.49±0.20 37.20±0.20 T sk ( ) Tight 33.87±0.45 A 34.37±0.46 A Moderate 33.39±0.29 B 34.08±0.22 B Loose 33.28±0.30 B 33.53±0.48 C T cl ( ) Tight 32.37±0.36 A 32.97±0.51 A Moderate 31.76±0.45 B 32.45±0.56 B Loose 31.56±0.38 B 32.13±0.54 C RH cl (%) Tight 75.12±16.29 A 96.93±1.59 A Moderate 70.45±18.96 B 93.59±2.63 B Loose 64.51±21.70 C 87.40±4.13 C Sweat efficiency (%) Tight 88.77±3.34 Moderate 92.11±3.40 Loose 92.32±3.18 a Same letters are not significantly different from one another.

166 INDIAN J. FIBRE TEXT. RES., JUNE 2012 periods. Analyses were performed with SPSS v17.0 (SPSS Inc, Illinois, USA). All data are presented as mean±sd. 3 Results and Discussion In this study, eight styles (I1-I8) of T-shirts were developed from the control sample (I0), all using the same fabric and having a similar cotruction, except for different sizes of clothing openings at neck and hem. The purpose of the present study was to test the influence of clothing openings on the thermophysiological respoes of wearers during the experiments in a moderate environment. In order to investigate the effects of different clothing openings on the thermophysiological respoes of wearers, the mean separation (Turkey) tests for significant effects of clothing neck opening and hem opening are presented in Tables 3 and 4 respectively. 3.1 Heart Rate and Rectal Temperature The mean heart rate (HR) and rectal temperature (T re ) for eight subjects across time for all garments are shown in Figs 3 (a) and (b). HR and T re show almost the same traition from the beginning to the end of the exercise for all clothing [Time: p<0.001], but do not demotrate a Time Clothing interaction (p>0.05). Varying design of clothing openings does not significantly increase (or decrease) HR or T re of wearers throughout the whole experiments. Meanwhile, there are no differences in HR and T re between T-shirts with different clothing opening desig at neck or hem during the experiments (Tables 3 and 4). Given that the treadmill speed is kept cotant for any subject during exercise, this would be anticipated. Thus, the thermoregulatory stress associated with the wearing of clothing with different opening desig used in this study is found to be similar. 3.2 Temperature Measurements and Microclimate Relative Humidity The changes in mean weighted skin temperature for all clothing are shown in Fig. 4. The temperature changes over time [Time: p<0.001]. Sample I1 results in a higher T sk when compared with all other clothing throughout the whole experiment, and during both exercise and recovery periods, samples I4 and I6 induce lower T sk when compared with other clothing, but there are no significant differences among clothing (p>0.05) at any time points. Table 4 Turkey tests for significant main effects of hem opening on physiological measure during resting, exercise and recovery periods Variance Exercise period Recovery period Mean Grouping a Mean Grouping a HR (bpm) Tight 161.35±4.07 87.72±8.55 Moderate 159.00±5.04 82.80±6.37 Loose 161.22±4.03 86.00±8.20 T re ( ) Tight 37.51±0.25 37.24±0.22 Moderate 37.50±0.18 37.25±0.16 Loose 37.44±0.19 37.14±0.12 T sk ( ) Tight 33.82±0.51 A 34.29±0.53 A Moderate 33.40±0.22 B 33.94±0.37 B Loose 33.33±0.36 B 33.74±0.52 C T cl ( ) Tight 31.98±0.45 A 32.96±0.54 A Moderate 31.87±0.60 B 32.38±0.61 B Loose 31.84±0.52 B 32.20±0.50 B RH cl (%) Tight 74.62±19.07 A 96.39±2.05 A Moderate 68.46±14.93 B 93.80±4.02 B Loose 67.00±16.46 B 92.73±4.80 B Sweat efficiency (%) Tight 89.07±2.89 Moderate 91.48±3.22 Loose 92.64±3.95 a Same letters are not significantly different from one another.

ZHANG et al.: EFFECTS OF CLOTHING VENTILATION OPENINGS ON THERMOREGULATORY RESPONSES 167 Fig. 3 Heart rate (a), and rectal temperature (b) for all clothing during the experiments (data shown as mean±sd) Fig. 4 Mean weighted skin temperature for all clothing during the experiments (data shown as mean±sd) A comparison of changes in the clothing microclimate temperature (T cl ) and relative humidity (RH cl ) at the chest level for all clothing are shown in Figs 5 (a) and (b) respectively. The T cl and RH cl both change dramatically during exercise [Time, p<0.001] and also demotrate a significant Time Clothing interaction [Time Clothing, p<0.05]. No significant Fig. 5 Clothing microclimate temperature (a), and relative humidity (b) at chest level for all clothing during the experiments (data shown as mean±sd) differences are observed among clothing for T cl during the pre-rest and exercise periods (p>0.05). However, during the latter half of recovery period, T cl is significantly higher for sample I1 than all other clothing samples ( *, p<0.05). The RH cl is found to be almost the same throughout the whole experiment for all clothing, and no significant differences are observed for RH cl among clothing (p>0.05) at any time points. High humidity in the microclimate may lead to inefficient evaporation of sweat from the skin s surface and thus increases skin wettedness 28. According to numerous papers dealing with clothing thermal comfort 29, a person remai in a neutral or comfortable condition thermally when the microclimate is maintained at temperature 32 ±1 C and relative humidity 50±10% under any environmental conditio. The dark areas in Fig. 5 are representative of the comfort zone of wearers. During pre-rest period, the human body produces little sweat or saturated water vapor, the RH cl for all clothing are stable and remained at less than 60%. However, the T cl

168 INDIAN J. FIBRE TEXT. RES., JUNE 2012 gradually increases with time in clothing with tight neck opening, which mea that additional body heat is generated and body temperature increases due to the lack of sufficient air-flow even in a stationary condition. During exercise, the RH cl does not increase right after running and start sweating; there is a delay in the period ranging from 5min to 10min, in particular, the oet of perspiration for the clothing with tight neck opening is about 5min earlier than that for the clothing with loose neck opening. When the subjects finish the exercise, the RH cl reaches a peak in a couple of minutes and then begi to decrease. Although the resting recovery period is only 10min, the influences of different neck openings on the microclimates show different trend. For the clothing with loose neck opening, the RH cl remai at a lower level of relative humidity of 87%. In contrast, the RH cl for the clothing with tight neck opening are still maintained at a high level (nearly to 100%), and all participants feel obvious thermal discomfort as compared to other clothing. The results thus support the hypothesis that a reduction in air exchange due to tight clothing opening will increase moisture concentration in microclimate and increase feelings of discomfort 30. According to Tables 3 and 4, the temperatures T sk, T cl and RH cl are significantly affected by varying design of clothing openings. During exercise, significant differences are observed in T sk, T cl and RH cl between clothing with tight opening and other two opening styles (p<0.05) at neck or hem respectively. These differences can be explained by comparing the ventilation areas of clothing openings to the thermophysical results. The tight clothing opening studied is cotructed to limit the convective exchange between the clothing microclimate and the external environment with added elastic at neck or hem, that is the ventilation areas of clothing openings are zero. Larger sizes of clothing opening suggest larger ventilation rates. T sk, T cl and RH cl reduce with increased air-flow due to a greater ventilation area, as forced convection by air-flow is known to increase the removal of heat from the body to the atmosphere 13, 22. However, there is no difference between the moderate and the large openings (p>0.05) at neck or hem during exercise, though the large opening style shows slightly lower values of measurements than does the moderate style. This phenomenon is mainly dependent on the fabric s air permeability to directly trafer heat from body by force convection during exercise. As a result, the effect that different clothing openings (from moderate to large) have on T sk and T cl would be reduced. During recovery period, the influence of clothing neck opening on thermal regulation increases significantly after the subjects complete the exercise and start their resting period. Significant differences are observed in T sk, T cl and RH cl between clothing with three different neck openings (p<0.05). It can be explained by the fact that when the exercise stops, heat loss by forced convection also stops. It is the natural convection through clothing openings that play the more important role, which helps to release the warm and wet air out. For the existence of a vertical updraft normally caused by the heat released from the skin 31, coequently the area of upper clothing opening is more important to release heat than the lower opening of clothing. Therefore, the larger the ventilation area of clothing neck opening, the greater is the natural convective exchange, caused in the clothing. Comparatively, not all desig in clothing hem opening are so effective in improving thermoregulation of the wearers. With only the tight hem opening it shows a significant difference as compared to the moderate and the loose hem openings, and there are no significant differences between the latter two clothing hem opening styles. 3.3 Body Mass Loss and Sweat Efficiency The mean values of body mass loss, sweat in clothing and sweating efficiency calculated before and after each test are summarized in Table 5. Mean body mass loss ranges from 198.33g to 266.67g and does not differ between tested clothing (p>0.05). The sweat trapped in clothing is found to be higher for samples I1 and I2 compared to all other clothings, but the difference is not significant (p>0.05). The overall average percentage change in sweat efficiency as compared to the control piece (sample I0) is Table 5 Body mass loss, sweat in clothing and sweating efficiency observed in each of tested clothing during the experiment Clothing Body mass loss, g Sweat in clothing, g Sweating efficiency, % I0 208.33±57.86 14.37±3.52 93.11±1.05 I1 266.67±75.20 33.93±3.30 87.13±1.22 I2 251.67±53.98 30.49±4.55 87.70±0.86 I3 250.00±88.32 20.13±6.97 91.49±3.81 I4 238.33±101.89 15.61±5.15 93.27±2.70 I5 266.67±62.09 27.08±7.45 89.59±3.40 I6 233.33±71.57 15.02±8.59 93.82±3.26 I7 241.67±89.89 22.23±2.54 90.51±1.36 I8 226.67±77.60 14.69±2.42 93.27±1.82 Values are mean±sd.

ZHANG et al.: EFFECTS OF CLOTHING VENTILATION OPENINGS ON THERMOREGULATORY RESPONSES 169 Table 6 Subjective ratings of thermal seation, moisture seation and comfort Clothing Thermal seation Moisture seation Comfort Before After Before After Before After I0 0.0±0.00 0.58±0.38 1.08±0.20 2.00±0.63 1.17±0.26 1.33±0.26 I1 0.25±0.27 1.00±0.63 1.17±0.26 2.67±0.82 1.75±0.52 2.17±0.52 I2 0.17±0.26 0.75±0.42 1.17±0.26 2.42±0.80 1.67±0.61 1.93±0.61 I3 0.17±0.26 0.58±0.38 1.08±0.20 2.08±0.58 1.68±0.58 1.93±0.61 I4 0.0±0.00 0.42±0.20 1.00±0.00 2.08±0.49 1.17±0.20 1.25±0.27 I5 0.0±0.00 0.50±0.32 1.08±0.20 2.00±0.63 1.25±0.27 1.50±0.32 I6 0.0±0.00 0.33±0.26 1.08±0.20 1.83±0.41 1.00±0.00 1,2,3 1.17±0.27 1,2,3 I7 0.0±0.00 0.50±0.45 1.00±0.00 1.92±0.58 1.25±0.27 1.50±0.32 I8 0.0±0.00 0.33±0.26 1.00±0.00 1.92±0.49 1.00±0.00 1,2,3 1.17±0.27 1,2,3 Values are mean±sd. Superscripts indicate statistically significant differences (p<0.05) between tests: I1=1; I2=2; I3=3. Fig. 6 Overall average percentage change in sweat efficiency relative to the control piece for all clothing during the experiments (data shown as mean±sd) shown in Fig. 6. All clothing show difference in sweat efficiency compared to control. The lowest sweat evaporation efficiency is observed in sample I1 (-6.43±0.25%), followed by samples I2 (-5.78±0.14%), I5 (-3.75±4.74%), I7 (-2.75±2.56%) and I3 (-1.68±5.20%). Samples I4, I6 and I8 exhibit a different trend than other clothing. Values are 0.22±4.04%, 0.81±4.64%, and 0.17±0.82% respectively. In a warm environment, the sweat loss can be coidered as an index of the physiological strain from thermal origin 1,32. Higher value of sweat evaporation efficiency indicates a higher ability to release liquid and moisture through garment, thus helping to reduce body heat storage of the wearers during exercise. However, as shown in Tables 3 and 4, varying design of clothing openings does not have significant effects on sweat efficiency. The major reason for this is probably a greater physiological stress may be needed to see differences by increasing the exercise time or inteity. Thus, a significant increase in work inteity could produce a sufficient heat load during which the clothing with larger ventilation opening would prove beneficial in promoting evaporation of sweat during exercise. On the other hand, the environmental conditio could be changed, specifically, by increasing wind. Larger ventilation opening will result in more heat loss through convection in the environment with wind. Moreover, the differences in thermal comfort and physiological parameters are found in highly air permeable T-shirts. It leads to the idea that physiologically significant may be found in air impermeable (protective) clothing. Future studies may need to investigate clothing made from air impermeable clothing fabric in an environment with or without wind. 3.4 Subjective Respoes The ratings of thermal seation, sweating seation and comfort, recorded from the subjects, are listed in Table 6. Generally, comfort seation is rated higher for clothing with tight neck openings before and after exercise, significantly in comparison to clothing with large neck openings (p<0.05).thermal and sweating seatio do not differ significantly between tested clothing (p>0.05) before and after exercise. Most subjects express complaints regarding the tight neck opening of T-shirts discomfort. 3.5 Body Heat Storage The mean body heat storage during exercise and recovery periods for all clothing is shown in Fig. 7. It can be seen that the rise in heat storage increases in

170 INDIAN J. FIBRE TEXT. RES., JUNE 2012 Table 7 Pearson product moment correlatio between heat storage and ventilation area of clothing openings Variable Correlation coefficient Heat storage during exercise Ventilation area of neck opening -0.674 ** Ventilation area of hem opening -0.294 Heat loss during recovery period Ventilation area of neck opening -0.494 * Ventilation area of hem opening -0.299 * Correlation, significant at the 0.05 level (2-tailed). ** Correlation, significant at the 0.01 level (2-tailed). Fig. 7 Mean heat storage during exercise and recovery periods and final residual heat storage for all clothing (data shown as mean±sd) all clothing due to exercise, and decreases when the subjects stop running. Sample I6 retai lower amount of heat than all other clothing during exercise, and the reduction in body heat storage during recovery period is found to be lowest in sample I1. However, there is no significant difference in body heat storage among different clothing either during exercise or during recovery period (p>0.05). Coidering the residual body heat storage throughout the whole experiment, the significant difference observed in sample I6 is lower than in all other clothing ( #, p<0.05). The residual body heat storage is also significantly higher in samples I1 and I2 when compared with other clothing ( *, p<0.05), except for sample I3. The correlatio between heat storage and ventilation area of clothing openings is shown in Table 7. Heat storage during exercise and recovery periods is also significantly reduced as the ventilation areas of neck opening increase (p<0.05). However, the increase in the ventilation area of hem opening is not so effective in improving heat trafer (p>0.05). Again, it indicates that the neck opening plays a more significant role to improve heat trafer than the hem opening. If the body stay still, the air between the clothing and the skin surface tends to move through clothing upper opening because of natural convection, so that an increase in the ventilation area of neck opening would promote the natural convection by such chimney effect. This ventilative effect would contribute towards heat release and sweat evaporation so as to make the wearer feel cooler and more comfortable. On the basis of calculated correlatio between the studied variables, the heat storage during exercise and recovery periods has a significant negative relation with the ventilation area of neck opening. It shows that the larger the ventilation area of neck opening, the higher is the rate of heats traferred from the skin to the environment, and thus the more comfortable microclimate for the wearers. 4 Conclusion 4.1 Varying design of clothing openings at neck or hem does not significantly affect the HR, T re and sweat efficiency of wearers during both exercise and recovery periods. 4.2 During exercise, tight openings at neck or hem significantly affect the T sk, T cl and RH cl of wearers. There are no differences between the moderate and the large openings. During recovery period, the neck opening plays a more significant role to improve thermoregulatory respoes of wearers. The larger the ventilation area of clothing neck opening, the greater is the thermophysiological comfort possessed by wearers. 4.3 Tight neck opening of T-shirts causes significantly uncomfortable seation on wearers. Thermal and sweating seatio do not differ significantly between varying design of clothing openings at neck or hem. 4.4 Heat storage during exercise and recovery periods is significantly reduced as the ventilation areas of neck opening increases. However, increase in the ventilation area of hem opening is not so effective in improving heat trafer. 4.5 The study will be useful for designers to be able to determine the effects of clothing openings on reducing physiological strain and develop garments that can enhance thermoregulation in total clothing system. It is recommended that the T-shirt with loose neck opening and moderate hem opening is the best one in releasing heat from the body, and the pumping effect of this design is also the most effective during exercise and recovery periods.

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