Sports Bra Restriction on Respiratory Mechanics during Exercise.

PURPOSE: We set out to understand how underband tightness or pressure of a sports bra relates to respiratory function and the mechanical work of breathing ( during exercise. Our secondary purpose was to quantify the effects of underband pressure on O2 during submaximal running.

METHODS: Nine highly trained, female runners with normal pulmonary function completed maximal and submaximal running in three levels of underband restriction: loose, self-selected, and tight.

RESULTS: During maximal exercise, we observed a significantly greater during the tight condition (350 ± 78 J/min) compared to the loose condition (301 ± 78 J/min; p < 0.05), and a 5% increase in minute ventilation () during the tight condition compared to the loose condition (p < 0.05). The pattern of breathing also differed between the two conditions; the greater maximal during the tight condition was achieved by a higher breathing frequency (57 ± 6 vs. 52 ± 7 breaths/min; p < 0.05), despite tidal volume being significantly lower in the tight condition compared to the loose condition (1.97 ± 0.20 vs. 2.05 ± 0.23 L; p < 0.05). During steady-state submaximal running, O2 increased 1.3 ± 1.1% (range: -0.3 to 3.2%, p < 0.05) in the tight condition compared to the loose condition.

CONCLUSIONS: Respiratory function may become compromised by the pressure exerted by the underband of a sports bra when women self-select their bra size. In the current study, loosening the underband pressure resulted in a decreased work of breathing, changed the ventilatory breathing pattern to deeper, less frequent breaths, and decreased submaximal oxygen uptake (improved running economy). Our findings suggest sports bra underbands can impair breathing mechanics during exercise and influence whole-body metabolic rate.