Do women with smaller breasts perform better in long-distance running?

Literature has established that a range of physiological, biomechanical, and training variables influence marathon performance. The influence of anthropometric characteristics has also received attention. However, despite major marathons exceeding 40,000 participants and approximately a third of these runners being female, no data exist on the influence of the breast on running performance. This cross-sectional study aimed to explore the impact of breast mass on marathon finish time. One hundred and sixty-eight of 321 female marathon runners contacted completed an on-line survey focusing on marathon performance during the 2012 London marathon. Participants were categorised as smaller (<500 g, 54%) or larger breasted (>500 g, 46%). Regression analysis identified that 24% of marathon performance variance could be explained by body mass index (BMI), but breast mass improved the model to explain 28% of performance variation. The model determined that for women with 32/34 or 36/38 underband each increase in cup size equates to a performance decrement of 4.6 min or 8.6 min, equivalent to 34.4 min difference between a woman with 36A compared to 36DD breast size. Larger breasted runners had greater BMIs, completed less marathons and had slower marathon finish times (316 ± 48 min) compared to smaller breasted runners (281 ± 51 min). Twenty-five per cent less larger breasted women finished in the fastest quartile. These results suggest that differences in breast mass are an important factor for female athletes and should be considered in future research in this area.