Running shoes aside, it’s the most important piece of gear a female runner puts on her body. But for all the time (and money) you spend debating the level of cushioning you need and tracking the miles you logged on a pair of sneakers, how often do you think about how you’re protecting your boobs on the run?

How’s this for a statistic: At least 32 percent of female runners report discomfort as a result of an ill-fitting sports bra, according to research published in The British Medical Journal. Discomfort doesn’t just mean sore breasts; it could mean anything from straps digging into shoulders, a bottom band that’s too tight, lack of ventilation, and even chafing.

You may be surprised to hear that all that discomfort is actually affecting running performance. Women lose up to four centimeters of stride length due to poorly controlled breast movement while running—which, over the length of a marathon, could translate to running an extra mile, according to a recent study conducted by Brooks Running Co. in conjunction with the University of Portsmouth.

“When women run without adequate support, research also reveals more muscle activity in the upper body as women may tense to try and limit how much their breasts move,” explains Brogan Horler, a researcher at the University of Portsmouth who studies breast motion and health. “We’ve also seen increases in ground reaction forces, which may be linked to a runner attempting to cushion their strides to limit breast movement, and increases in levels of perceived exertion.”

This is all because bras haven’t changed that much since the first jog-bra—in which two jock straps were disassembled and sewn together to create compressive cups—was released in 1977, explains LaJean Lawson, Ph.D., adjunct professor of exercise and sport science at Oregon State University and long-time consultant for Champion. The idea of breast support for sport wasn’t new, it was just the first time someone did something about it besides binding them in cloth or leather or hijacking a corset with slightly more flexible material.

By 1984, sports bras had evolved enough to include compression and encapsulation technology: Compression sports bras literally compress the breasts to the body and work well for smaller breasted women (usually A-C cups), says Lawson, and encapsulation bras “divide and conquer” by separating each breast into its own cup and are better for women with D+ cups.

But it’s only been in the past few years that there’s been a true renaissance in sports bra design. In 2017, after two years of development, Lululemon released their Enlite bra, which features a new high-performance (read: lightweight and breathable) fabric called Ultralux, thick straps to mitigate shoulder pain, and cups that don’t just bounce up and down, but move with the breasts in all directions for more natural motion.

The following year, Reebok launched the PureMove Bra, featuring Motion Sense Technology fabric that adapts and responds accordingly to the shape and velocity of breast tissue, and the type and force of movement (i.e. it stretches less for high-impact workouts like running).

In the spring of 2019, Nike expanded its sports bra sizes, now delivering 57 styles across three support levels in sizes ranging up to an impressive 44G. They also updated the Fe/Nom Flyknit bra, which uses the same Flyknit technology in the company’s shoes to ditch the bulk of high-impact bras making it 30 percent lighter than any other bra in their line.

In January, Brooks launched a new line of Run Bras that aims to reduce motion by up to 70 percent to increase comfort and running performance. One of the significant elements will be the hidden bottom band in the bras; the bottom band typically provides 80 percent of support, but the new design allows it to be flexible in the back and keep the support where you need it in the front under the breast tissue.

So yeah, if it’s been awhile, now is the time to upgrade your sports bra. Find six of our favorite options here.