Abstract:

Objective Current studies on human sweating have not involved the investigation of the distribution and sweating rate of women's breast, resulting in lack of systematic and scientific guidance on women's bra design. To fill this knowledge gap, this research aims to investigate the distribution of breast sweating locations, sweating rates in different parts of breast and the average sweating rate, taking young women as research objects.
Method Fifteen young female participants were selected to proceed a series of sedentary sitting with a metabolic rate of 50-60 W/m² and medium-high intensity exercise with a metabolic rate of 200-250 W/m² at 26 ℃ and 50% RH environment condition. A new ″sandwich″ structured sweat absorptive patch proposed in this research was used to measure the overall distribution of breast sweating, dominant and recessive sweating rate and sweating rate variation under different exercise conditions (Fig. 1). A 1 cm × 1 cm medical sweat absorptive patch was used to measure the sweating rate in seven regions of A-G of breast (Fig. 6). Mean filtering, threshold segmentation and Sobel operator digital image processing were carried out on the obtained images of breast sweating distribution, and paired T test was performed on the obtained sweating rates in different areas to analyze their differences.
Results No significant difference in the sweating rate of left and right breasts was found after independent samples test. The distribution of dominant breast sweating was identified. The annular region around BP (breast point) with a radius of about 1 cm was the first to sweat, then the rim ring area near the front chest and armpit with a radius of about 0.5 cm began to sweat soon afterwards. The above two annular regions continued to expand until the entire cup was soaked through (Fig. 4). Thermal imaging of female upper-body was taken before and after the 30 min medium-high intensity exercise, which showed that the temperature of front chest and mammary gland region were the highest resulting in early sweating. The results showed significant differences in sweating rates of breast areas A to G according to the Kruskal-Wallis H-test, the median test, and the Yorkhale-Tapastra test (P<0.05). The front chest region and annular region of BP were the two centers of high sweating. The maximum sweating rate near the front chest was 1.844 mg/(min·cm²), followed by sweating rate at 0.664 mg/(min·cm²) around the BP, and then the upper and lower edges of the breast (Tab. 5). It was found that breast average recessive sweating rate was (0.004 7±0.003 7) mg/(min·cm²) in sedentary state for six h, and the average dominant sweating rate was (0.405 5±0.178 4) mg/(min·cm²) in medium-high intensity exercise state for 30 min. During six 10-min intervals of medium-high intensity exercise, average breast sweating rate increased with the progress of exercise, reaching a peak at 0.409 mg/(min·cm²) at the 40th min, and finally slowly decreased to 0.356 mg/(min·cm²) due to the physical limitations and increase of fatigue.
Conclusion It is concluded that the annular region around the BP point and the annular region at the edge of the breast (especially near the front chest area) have relatively high sweating rate and thus perspired earlier. Therefore, it is suggested that in the moisture permeability design of the bra fabric, such as certain ventilation holes can be set in the above areas to accelerate the evaporation of sweat, which can improve the overall thermal and wet comfort of the bra. For daily wearing bras, it is suggested that the innovation of fabric fiber and the three-dimensional structure design of cup padding materials can refer to the recessive sweat rate. For sports bras, it is recommended that the optimal design of fabrics and cup padding materials should refer to the above mean and maximum sweat rate. The results from this research may be used to guide the optimal design ventilation hole distribution and to provide theoretical reference for the selection of moisture permeability index of bra cup material and the development of new materials for commercial purposes.

Key words: breast sweat rate, breast sweat distribution, dominant sweating rate, recessive sweating rate, bra thermal-wet comfort, bra design