Effects of fabrics with dynamic moisture transfer properties on skin temperature in females during exercise and recovery

Abstract

Based on the physiological nature of breast movement in exercising females, a sports bra made of fabric with dynamic moisture transfer properties was developed to improve female thermal comfort. This study aimed to investigate the effects of fabrics with dynamic moisture transfer properties on breast skin temperature, and the thermal physiological and psychological response of women while wearing the sports bra during exercise and recovery. Ten healthy women exercised in random order with two types of sports bra with or without the dynamic moisture transfer properties and then performed a 20-minute short-duration high-intensity exercise and rest to recover under thermoneutral conditions. Heart rate, body core temperature, skin temperature, body mass and thermal psychological subjective sensations were investigated during exercise and recovery. The results indicated that in the running state, the local breast skin temperatures of sports bra made of fabrics with dynamic moisture transfer properties (33.427 ± 0.087℃) are significantly lower than bras without these dynamic moisture transfer properties (33.964 ± 0.055℃) (P < 0.01). During the exercise and recovery, the thermal psychological subjective sensation for the two types of fabrics were very similar, whereas the body mean skin temperature was revealed to undergo greater decreasing effects in sports bras made of fabrics with dynamic moisture transfer properties than those without the dynamic moisture transfer properties (P < 0.05). These results provide novel information that usage of fabrics with dynamic moisture properties in sports bras could improve thermoregulation to benefit exercising women’s thermal comfort in terms of decreasing local breast skin temperature.

Keywords

fabrics with dynamic moisture transfer properties sports bra breast skin temperature thermoregulation

Physiological structures supporting the breast include the skin, Cooper's ligaments and the pectoralis fascia,¹ which provide weak intrinsic support on breast movement during physical activity. Sports bras, as breast supports, may reduce breast pain and movement during exercise, so have been advocated as a necessary garment for exercising females.^2,3 Most studies predominantly emphasize research concern in the support function of sports bras;^3,4 however, a limited number of studies have investigated the function of sports bras in regard to thermal comfort. It has been reported recently that the material properties of bras could affect female thermal comfort and post-exercise skin temperature, due to an extra layer of sports bra having a negative cooling ability in relation to the breast and thus affecting thermal comfort.⁵ During exercise, heat produced in the muscles generates thermal stress, which increases core and skin temperatures,⁶ and may influence exercise performance.^7,8 Evaporation of sweat is the main method of body heat dissipation during exercise.⁹ Clothing has the ability to affect the amount of sweat produced and the level of evaporation.⁷ It seems that good properties of moisture transfer in clothing may decrease skin wetness and increase sweat evaporation, and therefore benefit thermoregulation during exercise.

Previous studies have suggested that differences in clothing fabric or construction could affect the sweat accumulation and disturbances of thermoregulation.^9–11 Dynamic water pumping fabrics (DWPF) are novel single jersey tuck stitch with properties of dynamic moisture transfer, which are designed and fabricated based on the arrangement of hydrophilic/hydrophobic yarn and novel fabric structure for moisture transfer.^12,13 The key function of DWPF relies on the inspiration of fabric stretch and recovery to wipe out the sweat under body movement and then finally improve thermal comfort. Based on the physiological character of breast movement for exercising females, DWPF is a good option for the cup area of sports bras. However, it is still not clear whether the usage of DWPF for sports bras could induce different influences on thermal physiological and psychological responses for women during and after short-duration high-intensity exercise under thermoneutral conditions.

DWPF sports bras and control (single jersey) bras were made with the same material of 75D polyester (35%), 40D Lycra (8%) and 40S cotton (57%), but with different fabric structures. We hypothesized that the local breast skin temperature may decrease when the subject wears sports bras with fabrics having dynamic moisture transfer properties. In addition, the important variables of thermal-physiological and perception sensation response may be affected by wearing sports bras with dynamic moisture transfer properties in terms of decrease of local breast skin temperature.

Methodology

Experimental garments

A sports bra for female breast thermal comfort was designed and fabricated (Figure 1). In brief, the same type of sports bra was manufactured with the same material and structure, except the bra cups, which were knitted with the structure of fabrics with the DWPF or single jersey. A Santoni SM8-TopS, 8-feeder, 14-inch diameter and 28-gauge seamless knitting machine was used to knit the fabrics. The specifications of dynamic water pumping single jersey tuck stitch and plain single jersey are shown in the Table 1. The physical properties of the two kinds of fabrics are summarized in Tables 2 and 3. All testing underwent six repetitions.

Figure 1.

The sports bra tested: (a) front; (b) back; (c) side; (d) up. The cup was knitted from dynamic water pumping fabrics or single jersey.

Table 1.

The specifications of dynamic water pumping fabrics and single jersey

No.	Fabrics name	Fiber content	Microphotography
No.	Fabrics name	Fiber content	Face	Back
1	Dynamic water pumping fabrics (single jersey tuck stitch)	75D polyester (35%); 40D Lycra (8%); 40 S cotton (57%)
2	Single jersey	75D polyester (35%); 40D Lycra (8%); 40 S cotton (57%)

Table 2.

Physical properties of the dynamic water pumping fabrics for the cup of the sports bra (n = 6)

Properties	Dynamic water pumping fabrics	Standard	Equipment
Weight (g/m²)	323.10 ± 3.13	ASTM D 3376	Balance, fabric cutter
Thickness (mm)	1.32 ± 0.02	ASTM D 1777	SDL fabric thickness tester
Water vapor permeability (g/m²/24 h)	1051.84 ± 32.37	ASTM E96	Balance, wide-mouse vessels
Air resistance (kPa·s/m²)	1.46 ± 0.44	KES method	KES air-permeability tester
Thermal insulation (CLO)	0.18 ± 0.02	KES method	KES thermal LABO II Tester
Thermal conductivity (W·m⁻¹·K⁻¹)	0.08 ± 0.00	KES method	KES thermal LABO II tester
Overall moisture management capacity	0.58 ± 0.03	AATCC 195	Moisture management tester (MMT)

ASTM: American Society for Testing and Materials; KES: Kawabata evaluation system; AATCC: American Association of Textile Chemists and Colorists.

Table 3.

Physical properties of the single jersey for the cup of the sports bra (n = 6)

Properties	Single jersey	Standard	Equipment
Weight (g/m²)	286.97 ± 2.35	ASTM D 3376	Balance, fabric cutter
Thickness (mm)	1.18 ± 0.02	ASTM D 1777	SDL fabric thickness tester
Water vapor permeability (g/m²/24 h)	972.75 ± 18.22	ASTM E96	Balance, wide-mouse vessels
Air resistance (kPa·s/m²)	1.02 ± 0.02	KES method	KES air-permeability tester
Thermal insulation (CLO)	0.18 ± 0.01	KES method	KES thermal LABO II tester
Thermal conductivity (W·m⁻¹·K⁻¹)	0.09 ± 0.00	KES method	KES thermal LABO II tester
Overall moisture management capacity	0.33 + 0.01	AATCC 195	Moisture management tester (MMT)

ASTM: American Society for Testing and Materials; KES: Kawabata evaluation system; AATCC: American Association of Textile Chemists and Colorists.

Subjects

Ten healthy, pre-menopausal women were recruited as subjects. The mean value of their age, body mass, and BMI index were 28.1 ± 6.3 years, 54.69 ± 4.79 kg and 20.43 ± 1.54, respectively. In this study, participants’ bra size was assessed by a trained bra fitter, following the recommendations of McGhee and Steele.¹⁴ The bra under-band size of all subjects ranged from 32 to 36 in, and had a bra cup size B. All testing was undertaken for a time point that was not in the participants’ menstrual cycle. Before testing, each subject signed a consent form approved by the Human Subjects Ethics Sub-Committee of the Hong Kong Polytechnic University.

Measurements

The body core temperature (Tre) and body skin temperature (Tsk) were measured at six time points: resting (Pre), warm-up (Wp), running (Run20) and resting (RT10, RT20, RT30). Tre was measured with a CorTemp™ Ingestible Core Body Temperature Sensor (HQ Inc. U.S.A). Tsk was detected using surface skin temperature probes (Gram Corporation LT-8 A, Saitama, Japan) at five sight sites:¹⁵ chest, upper arm, thigh, lower leg and local chest. The five sites of skin temperature measurement are shown in the Figure 2. Heart rate (HR) was measured every minute using a Polar Heart Rate Monitor (Polar Electro, USA).

Figure 2.

Five sites of skin temperature measurement. A: chest; B: upper arm; C: thigh; D: lower leg; E: local chest.

Psychological subjective sensations about the cup of the sports bras were gathered by rating the five sensations of wetness, coldness, breathability, itchiness, softness and overall comfort (Table 4) using a visual analogue scale (VAS) (rate 1–7).¹⁶ The rating of perception was reported by the participants at each scheduled time before, during and after exercise. The body mass of each subject was determined by measuring their nude mass before exercise and after exercise for the estimation of sweating (E-SNO-PSL-150 kg, Sam Hing Scales Fty. Ltd). The body sweat loss was calculated by subtracting body mass.

Table 4.

Subjective sensation questionnaire

Damp	\|1- - - -2\|- - - -3\|- - - -4\|- - - -5\|- - - -6\|- - - -7\|	Dry
Hot	\|1- - - -2\|- - - -3\|- - - -4\|- - - -5\|- - - -6\|- - - -7\|	Cool
Air-tight	\|1- - - -2\|- - - -3\|- - - -4\|- - - -5\|- - - -6\|- - - -7\|	Breathable
Itchy	\|1- - - -2\|- - - -3\|- - - -4\|- - - -5\|- - - -6\|- - - -7\|	Non-itchy
Rough	\|1- - - -2\|- - - -3\|- - - -4\|- - - -5\|- - - -6\|- - - -7\|	Soft
Uncomfortable	\|1- - - -2\|- - - -3\|- - - -4\|- - - -5\|- - - -6\|- - - -7\|	Comfortable

Experimental protocol

A parallel, randomized blinded design wear trial was carried out to verify the hypothesis that a sports bra with dynamic moisture transfer properties may decrease breast skin temperature and advance thermal and wear comfort under thermoneutral conditions during exercise and recovery. The temperature of the lab was set to the thermoneutral conditions of 27℃ with an average relative humidity of 46%. The reason to set the lab at this temperature is that all the key routes of heat exchanges, at this temperature, are still available for heat loss and the body temperature can be controlled by changes in peripheral blood flow when at rest.¹⁷ There was no fan used during this exercise.

Subjects were wearing the sports bra only on their upper body and were wearing only the same type of sports pants during this experiment. The subject’s nude body mass was measured first. Before testing, subjects wore the sports bra and then rested for 10 min on a chair in a climate chamber before warm-up. Tre, Tsk and HR were measured to provide control values. During the rest state, the subjective thermal sensations were recorded. To warm up, participants completed a treadmill walk for 5 min at 4.5 km/h (Mercury, h/p/cosmos, Germany). The subjects next performed a 20 min exercise at 7 km/h, and then rested in a chair for 30 min to recover. HR was recorded every 1 min. All body skin temperatures were recorded continuously every 2 s. The subjective psychological sensations were recorded at another five time points. The entire experimental procedure lasted 65 min. The subject’s nude body mass was measured after recovery.

Data analysis

The equation of Ramanathan¹⁵ – mean skin temperature=0.3 (T_ches_t + T_arm)+0.2 (T_tight + T_lower_leg) – was used in this experiment to calculate mean skin temperature. A two-factor analysis of variance (ANOVA) with repeated measures was applied to analyze the patterns of core temperature, HR, mean skin temperature, local chest skin temperature and psychological subjective sensation. The main effects included fabrics and the time of six sessions. A one-way ANOVA was performed on the data in regard to the local breast skin temperature and sweat loss. The alpha level was set at 0.05: if reported at the P < 0.05 level it was regarded as a significant difference; if at P < 0.001 it was regarded as a very significant difference. The data were statistically analyzed using PASW (Version 18) (SPSS Inc., Quarry Bay, Hong Kong).

Result

Figure 3 shows the significant temporal changes (F = 95.393, P < 0.01) in local chest skin temperature between two types of fabrics during exercise and recovery. Briefly, after a slight increase in the Wp session, the regional chest skin temperature decreased in the following three sessions and then rose in the last sessions with a small increase. No significant difference was found in local chest skin temperature between the fabrics. However, a significant time by fabrics interaction effect (F = 13.066, P < 0.01) was detected in local chest skin temperature. In addition, one-way ANOVA shows that local chest skin temperature was significantly lower for the DWPF sports bra than the single jersey sports bra in the sessions of Run20, RT10 and RT30 (F = 27.086, P < 0.01; F = 11.291, P < 0.05; F = 8.820, P < 0.05). It should be noted that, when wearing the DWPF sports bra, the local breast skin temperatures (33.427 ± 0.087℃) were significantly lower than when wearing the single jersey sports bra (33.964 ± 0.055℃) in the running session (Run20).

Figure 3.

Comparison of temporal changes in local chest skin temperature between the two types of fabrics during exercise and recovery. Values are means (the standard error of the mean - SEM). One-way analysis of variance for the two kinds of fabrics in different time sessions; when appropriate, statistical significance is indicated: *P < 0.05; **P < 0.01.

A significant temporal change (F = 102.894, P < 0.01) is illustrated in Figure 4 for body core temperature, which increased significantly after warm-up for both types of fabrics during exercise and decreased gradually after 20 min of recovery. Repeated measure analysis showed no significantly different effects of fabrics on body core temperature; however, a significant time by fabrics interaction effect was found (F = 12.561, P < 0.01). In terms of HR, Figure 5 shows a sharp increase following a 20 min run, which declined gradually within 30 min of rest. There was no difference between the two kinds of fabrics during exercise and recovery.

Figure 4.

Comparison of temporal changes in body core temperature between the two types of fabrics during exercise and recovery. Values are means (the standard error of the mean - SEM).

Figure 5.

Comparison of temporal changes in heart rate between the two types of fabrics during exercise and recovery. Values are means (the standard error of the mean - SEM).

Body mean skin temperature in Figure 6 draws a notable temperature change in six sessions. There was an obvious decrease in the last four sessions after a slight increase in the warm-up session. However, results concerning effects of fabrics on body mean skin temperature obtained from the repeat measure ANOVA show there was a significantly lower body mean skin temperature for the DWPF sports bra than for the single jersey sports bra (F = 115.891, P < 0.01). Effects of time (from the Pre session to the RT30 session) on body mean skin temperature measured by statistical analysis also showed a significant difference here (F = 8.864, P < 0.01), while it also differed significantly under the interaction effects from time by fabrics (F = 8.385, P < 0.01).

Figure 6.

Comparison of temporal changes in body mean skin temperature between two types of fabrics during exercise and recovery. Values are means (the standard error of the mean - SEM).

In conclusion, the factor of time caused a significant effect on the thermal physiological parameters, due to the subjects being involved in different experimental activities. In addition, the factor of fabrics generated a significantly different effect on body mean skin temperature. Significantly different interactions between the time factor (from the Pre session to the RT30 session) and fabrics were found in all thermal physiological parameters in this study. Whole body sweat loss from before exercise to recovery, however, did not differ between the single jersey sports bra and the DWPF sports bra (Figure 7).

Figure 7.

Whole body sweat loss (kg). Values are means (the standard error of the mean - SEM).

Figure 8 shows the subjective rating of psychological sensation for breasts under two types of fabric conditions. The effects of time, fabrics and their interactions on psychological concerned sensations are analyzed by the repeated measure ANOVA. In generally, the rating of the wetness, coldness, breathability and overall comfort sensations of the chest changes significantly during exercise and recovery (P < 0.05), but do not differ significantly in itchiness and softness sensations. Moreover, no significant difference is found in all psychological sensation listed under the fabric condition and both time and fabric conditions.

Figure 8.

Temporal changes in psychological sensation for the sports bra: (a) wetness sensation; (b) coldness sensation; (c) breathability sensation; (d) itchiness sensation; (e) softness sensation; (f) overall comfort sensation; in the two types of fabrics during exercise and recovery. Values are means (the standard error of the mean - SEM).

Discussion

The above results have clarified the hypotheses that the dynamic moisture transfer properties of fabrics for sports bra cups can significantly reduce local breast skin temperature during exercise. In addition, the body mean skin temperature showed a significant decrease for the DWPF sports bra, which may be due to the influence of the DWPF sports bra on local chest skin temperature during exercise. A reduction trend of skin temperatures, including both body mean skin temperature and local chest skin temperature during exercise, was found due to air movement created by exercise.¹⁸ It should be noted that the DWPF sports bra produced a lower local chest skin temperature in the Run20, RT10 and RT30 sessions than single jersey fabrics during exercise and recovery (P < 0.05). The decrease of local chest skin temperature may be explained as a result of the DWPF having the function of fabric stretch and recovery to wipe out sweat during body movement.¹² According to comparisons of physical characteristics between two types of fabrics, a relative higher physical characteristic of overall moisture management capacity in the DWPF, shown in Table 2, also could support this effect of decrease of local chest skin temperature. It is well known that evaporation of sweat is an effective method of heat elimination from the body during exercise, and finally causes the cooling effect.¹⁹ Previous researchers have reported that the properties and the design of clothing may influence the process of evaporation and heat dissipation through clothing, both in relation to body movements and the environmental condition.^11,20–24 In addition, moisture management properties have been reported that could accelerate liquid transfer from the skin surface to the opposite surface quickly and thus reduce the mean skin temperature.²¹ Consistent with the previous report, fabrics with dynamic moisture transfer properties applied in the cup of sports bras also could increase the sweat liquid transfer from the inner to outer layer, and then promote sweat evaporation, and finally decrease the breast skin temperature during exercise.

The body mean skin temperature returned to the pre-exercise level faster in the DWPF sports bra than the single jersey fabrics one in the RT30 session, which may be due to the high ability of sweat transfer of the DWPF sports bra in the running session (Run20) and the increase of evaporation in the first two recovery sessions (RT10 and RT20); thus, the breast skin temperature returned to the pre-exercise level faster than with the single jersey fabrics in the RT30 session.

Sports bras, as potential applications for breast health and comfort, undoubtedly should be considered as a basic requirement for exercising women. In this study, we found that the DWPF sports bra could enhance thermoregulation in terms of decreased body mean skin temperature, but could not significantly improve the subjective thermal and wear comfort for women in different activities. With regard to psychological wear comfort, it is generally accepted that the wider that moisture is distributed over the skin, the stronger the discomfort.^25,26 Some evidence also shows that thermal sensation and clothing sensation are associated with skin.^20,24 However, no significant differences were found for any of the psychological comfort sensations reported above under the fabric condition and both time and fabric conditions. This may be because the fabrics’ structure could not influence the breast psychological wear comfort sensation of exercising women in this study. This was similar to the results of Gavin et al.,²⁷ who reported that clothing fabrics do not affect comfort sensation responses during exercise in a moderately warm environment.

Conclusion

In summary, sports bras with cups knitted from different fabric structures with or without dynamic moisture transfer properties have been developed for exercising women’s breast thermal comfort. From the study, a hypothesis has been identified that fabrics with dynamic moisture transfer properties applied in the cup of sports bras could reduce breast skin temperature in the running state when subjects are performing a 20 min short-duration high-intensity exercise under thermoneutral conditions. In addition, changes in cup fabrics’ structure of sports bras to transfer sweat from the breast also could influence the body mean skin temperature and local breast skin temperature during exercise and recovery.

Footnotes

Funding

This work was supported by the Hong Kong Innovation and Technology Commission and Hong Kong Research Institute of Textile and Apparel (projects ITP/015/11TP, ITT/003/11TT, ITT/005/14TP and G-YM63) and the Guangdong Provincial Department of Science and Technology (projects 2012B050800002 and 2012B091000143).

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