The Impact of Breasts and Bras on Physical Activity Amongst Women and Girls: A Systematic Review and Meta-Analysis

BACKGROUND: Breast motion may cause breast pain in active women, which can negatively impact physical activity. Sports bras are essential pieces of sporting equipment and were designed to help women comfortably participate in sports and engage in physical activity. Thus, the purpose of this systematic review was to summarize how breasts and bras influence physical activity in women and girls. METHODS: A systematic review was conducted by performing electronic searches of PubMed, Physiotherapy Evidence Database, Cumulative Index to Nursing and Allied Health Literature, and Cochrane Central Register of Controlled Trials. Title, abstract, and full text screening were performed by two independent reviewers to identify articles investigating how breasts or bras impact physical activity related outcomes in women or girls. We performed meta-analyses to evaluate the effect of (i) breast size, (ii) bra type, and (iii) breast reduction on (i) breast pain, (ii) physical activity level, and (iii) breast biomechanics. Standardized mean differences and pooled standard deviations of outcome measures were calculated using the DerSimonian-Laird method. All meta-analyses were performed using SPSS Statistics Software. RESULTS: Of the 323 articles identified, 77 were included in the final analysis. The majority of articles studied participants who were 20-29 years old, identified as white, lived in Western countries, were non-athletes, and weighed between 45-65 kg (BMI: 18.5-29.9), while they were performing a running movement. Very few articles reported household income and ethnicity/race. Key themes investigated by this body of literature were breast biomechanics, breast pain, and physical activity levels. Meta-analyses revealed that women and girls with larger breasts reported more exercise-induced breast pain and experienced greater breast mediolateral velocity and anterior/poster acceleration during physical activity than women and girls with smaller breasts. Meta-analyses revealed that sports bras were associated with less breast pain during physical activity than standard bras. CONCLUSION: This body of literature largely studied a homogenous population, and there is a need for greater inclusion of women and girls who identify with under-represented minorities, with disability, who are post-menopausal, and who are overweight. Factors such as ethnicity/race and household income, were underreported in the literature, and studies of movement patterns beyond running are needed. Mediolateral breast velocity and anterior/posterior breast acceleration may be contributors to breast pain in women and girls with larger breasts, thus these biomechanical outcomes are of particular interest for future research and for consideration in sports bra optimization.