Thermal Comfort Design Of Sports Bras

Sports bras consist of multi-layer(shell fabric and cup cushion)that prevents heat and moisture transfer and reduces the thermal comfort.There are few studies on the thermal comfort of sports bras,which is mainly on the changes of skin temperature under bra area and the effect of cups on the thermal comfort of bras,no specific research on cushion materials of sports bras.After analyzing the factors affecting the thermal comfort of sports bras,the relevant properties of 10 cushion materials were tested.Two typical cushion materials(sponge and three-dimensional space knit material)were selected to make two sports bras of the same style.A wear trail experiment was developed to evaluate the thermal comfort of the sports bras and seven female undergraduate students volunteered to participate the experiments.Subjects randomly wore two sports bras together with a short sleeve T-shirt and a pair of short pants respectively in a warm environment(30℃,30%RH,0.4 m/s airflow).The exercise protocol consisted of 30min sitting rest,a 5min walking(5 km/h)for warming up,three cycles of alternation between 10min jogging(7 km/h)and 5min walking(5 km/h),followed by 30 min sitting rest to recover.The skin temperature(Tsk)and humidity,rectal temperature(Tre)and heart rate(HR)were measured,subjective feelings(hot,cold,humid,comfort and fatigue)were recorded.The results are as follows:(1)Heat conductivity of cushion materials is close to each other;when the materials absorbed water,the heat conductivity increased greatly,and reached a maximum when the material was saturated;it indicated that heat conduction can become a main way for the bust to release heat.(2)No significant difference of HR,Tre and mean Tsk was found between two bras;wearing bras formed different air layers on torso surface under the T-shirt,resulting the earlier cooling at the bust and the stomach than at the back and waist.(3)Significant difference of Tsk at the bust was observed between two bras and the difference was up to 0.63℃;since the 3D space knit cushion material which contains plenty of interstices absorbed sweat and transferred it,the heat conductivity seemed to increase quicker than the sponge material,resulting earlier cooling at the bust.It is concluded that wearing a bra can form different air layer under a T-shirt,resulting in different local Tsk changes during exercise;and the selection of cushion materials can affect the cooling at the bust surface,and further the thermal comfort of the bra.