Exponential Relationship Between Bra Underwire Rigidity and Breast Motion: Insights for Adaptive Bra Design and Manufacturing

ABSTRACT Sports bras function as a form of personal protective equipment, designed to minimize breast motion and pain. The sports bra design significantly affects breast support and discomfort. Although the use of underwire has been shown to enhance bra support, no quantitative data related to the relationship between underwire properties and bra performance has been published to guide designers and manufacturers in selecting underwire. This study aimed to quantitatively examine the relationship between underwire rigidity and breast motion and discomfort. Ten participants were recruited to perform treadmill running under six bra conditions: one without underwire and five with underwires of varying levels of rigidity. A decreasing trend was observed in vertical breast displacement, perceived breast movement, and discomfort as underwire rigidity increased. Significant exponential relationships were identified between underwire rigidity and vertical breast displacement. However, no significant associations were found for perceived breast movement and perceived breast discomfort. These findings underscore the importance of selecting appropriately rigid underwires for sports bras, under the tested conditions (young women with bra size 75 C performing treadmill jogging/running at 7.5 and 10 km/h using the same bra model), offering valuable insights into the design and manufacturing of sports bras in the underwear industry.