Saturday, March 9, 2024

Is Your Sports Bra Restricting Your Breathing?

I'll come straight to the point. Sports bras aren't always comfortable. Not only do the shouder straps slip and chafe sometimes, the bands are sometimes so tight around the rib cage that they are uncomfortable and restrict breathing.

Kipp and colleagues (2024) studied whether tight sports bras hinder breathing in runners. They had 9 international and/ or national competitive runners complete a series of treadmill tests while wearing a specially modified version of LuluLemon's Energy sports bra. The underband tightness around the RC can be increased or decreased with extra eye-and-hook attachments at the back.

The bra was also modified so that a small balloon catheter could be inserted into the underband to measure exactly how much pressure was being exerted as the runners breathed in and out.

In addition, the subjects had another balloon catheter inserted through their nose down into their esophagus to measure the internal pressures exerted with each breath by their lungs as they ran! Ouch. Check out the Instagram video Kipp posted here. Definitely worth a watch so you can appreciate what the subjects had to endure for this research.

That catheter allowed the researchers to calculate the "work of breathing" i.e. the energy used by the respiratory muscles to inflate and deflate the lungs. It has been calculated that it takes more than 10 percent of your total energy output during hard exercise.

The runs were done under 3 conditions. Once with the runners' self selected bra size, once with the bra tightened and once with it loosened. 

When the pressure on the band was tight, it was on average 16 % greater than in the loose condition. Going from self selected to tight did not change anything. However going from self selected to loose reduced oxygen (and energy) consumption. Overall difference between tight and loose conditions was between 1-2 percent in most subjects, with an average of 1.3 percent. 8 out of the 9 runners saw improvements in the loose condition. Not the 4 % change like what you get from the carbon plated super running shoes, but significant enough.

Kipp estimated that a 2 % change in oxygen consumption translates to a 3 minute improvement in the marathon time for a 3-hr marathoner runner. 

The reason for the efficiency difference is due to the tighter bra making the runners breathe differently. While running at VO2 max in the tight bra, the women had to breathe in more oxygen overall by breathing more quickly (57 versus 52 breaths per min). However they had to breathe more shallowly. 

That work of breathing took 16 percent more energy, which explains why overall whole body consumption was higher.  Secondary effects include the oxygen rich blood being diverted away from the legs to elsewhere.

It can be a serious problem if you wear your bra too tightly if you value a percent or two in performance. Kipp cited previous data suggesting that 70 % of women choose sports bras that are too small for them compared to a professional fit. If you're happy with your sports bra, you can ignore these findings.

The runners presumably chose a tighter than optimal bra because they wanted adequate support. However none of the women in the study reported that the loose condition was uncomfortable or provided inadequate support. 

A possible reason is that women select and try on sports bras at rest. None of the breathing parameters meaured in Kipp's study were affected at rest. It was only during hard exercise when the runners were breathing hard and inflating their lungs that problems emerged. 

It may be best to choose your sports bra based on how it feels during a hard workout rather how it felt at the store. Sports bra designs are much more than just tight the underband is. All the elite runners in this study had small to medium breasts. It also depends on the activity you are doing. 

There are more than enough models and patents amongst different brands for women to choose between insufficient support and excessive tightness. Pick what you need.

If your sports bra feels tight enough when you are exercising that you wonder if it may interfere with your breathing then it probably is.


Kipp S, Leahy MG and Sheel AW et al (2024). Sports Bra Restriction On Respiratory Mechanics During Exercise. Med Sci Sp Ex. DOI: 10.1249/MSS.0000000000003403

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