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The Painful Truth About Why Your Boobs Hurt When You Run

Let's get the discomfort off your chest and understand why the girls hurt and what you can do about it.

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If your boobs hurt when you run, you are definitely not alone. The struggle is very real—especially for women with larger cup sizes. A 2014 study out of the United Kingdom found that nearly one in five women say that factors related to their breasts—including excessive movement and being unable to find the right sports bra—have kept them from exercising.

Sports bra design has improved over the years, but even the best ones on the market are not going to solve all of your breast-related issues while running. Get to know a little bit about the cause of your discomfort in order to pin point the best mitigation strategies for you.

RELATED: Supportive Science: The Quest to Build a Better Sports Bra

Why Do My Boobs Hurt When I Run? Blame It on Displacement.

Breast movement and discomfort go hand in hand, explains Michelle Norris, a senior research associate at the University of Portsmouth. “What studies have found is that breast pain is linked to the displacement of the breasts—not just up-and-down movement, but also side to side and forward and backward,” she says. Breasts move an average of 10 cm in three directions during running, according to the university’s Research Group in Breast Health.

Women with larger breasts tend to experience more displacement and are more susceptible to pain, but that’s not to say women with smaller breasts are off the hook. All women can experience stretching of and damage to the Cooper’s ligaments, which hold the breasts onto the chest wall, preventing sagging.

The most important thing runners can do to remedy breast pain is to invest in a good sports bra, says Norris. A quality bra should fit properly, be comfortable and provide three-dimensional support. “Often  you’ll have to try on a lot of different sports bras to find one that works,” she says. Norris recommends mimicking running in the fitting room to see how the bra performs. And don’t reserve your best sports bra for speed workouts—breast displacement can happen just as much at slower speeds.

How to buy a sports bra.

It’s critical for all runners to find a good fit. Here’s what Norris looks for in a quality bra.

Under-band: The band should fit firmly around the chest and provide a shelf for the breasts. It shouldn’t slide around as you move—but it also shouldn’t be so tight that skin bulges over the band.

Cup: In some cases, an encapsulation bra, which has separate cups for each breast, can provide better support for running. Norris says choosing among an encapsulation, compression, or combination bra is a matter of preference. If you opt for a bra with separate cups, make sure the breasts are enclosed within the cups, with no overflow or gaping.

Straps: The straps should be tight enough to provide support without digging into the skin. The main support for the breasts should come from a firm band, not tight shoulder straps. Adjustable straps are a matter of preference.

Fabric: Check the seams on the inside of the bra to see if there are any that might rub against your skin and lead to chafing.

RELATED: 20 Sports Bras Runners Swear By

Hormones and Motherhood

Hormonal changes associated with the menstrual cycle—generally before and during one’s period—are another commonly reported reason for sore breasts among athletes and non-athletes alike. Swelling and general tenderness can cause boobs to hurt when you run. Runners who experience swelling, in particular, during that time of the month may want to invest in a different-sized sports bra designated specifically for those few days or week.

During the first trimester of pregnancy, hormones can cause increased blood flow and changes to breast tissue, adding weight to breasts and making them more sensitive, says Julie Levitt, an OB-GYN in Chicago. Breasts may become sensitive again in the third trimester as milk starts to appear. Levitt advises runners who are breastfeeding to nurse or pump before they go on a run. “The lighter and emptier the breast, the better,” she says.

It is important for pregnant women, new moms and those who have recently stopped nursing to get re-fitted for a sports bra with each transition, as both cup and rib cage sizing are likely to change.

RELATED: How to Train and Race Long Distances While Breastfeeding