A sports bra that is too restrictive can cause back pain. (Albina Gavrilovic/Shutterstock)
In a nutshell
- Too much support can backfire: Sports bras designed to eliminate all breast movement may actually increase stress on the spine, potentially raising the risk of back pain during running.
- Some bounce is beneficial: Controlled breast motion may act as a natural shock absorber, helping to dissipate forces and reduce spinal loading, especially in women with larger breasts.
- Balance is key: While support is important for comfort and reducing breast pain, bras that allow a bit of movement may offer better protection for your back than those that aim for zero bounce.
PORTSMOUTH, England — When shopping for a sports bra, do you search high and low for something with as much support as possible? You might want to reconsider. A new study from the University of Portsmouth suggests that ultra-supportive sports bras could increase stress on your spine during running, potentially leading to back pain.
The study, published in the European Journal of Sport Science, upends conventional wisdom about breast support during exercise. While manufacturers have long marketed “maximum bounce reduction” as the gold standard for sports bras, this study indicates that some breast movement may actually benefit spinal health.
The researchers explain that the movement of soft tissues in various body parts, like thighs and legs, has been shown to help reduce stress on joints. Breast tissue motion appears to follow this same pattern, potentially acting as a natural shock absorber.
Researchers used computer modeling to investigate how different levels of breast support affect the spine during running. The implications could change how we think about sports bra design and women’s athletic performance.
For years, women with larger breasts have been told that maximum support is essential for comfort and preventing pain during exercise. However, this new research suggests there’s an optimal middle ground where some controlled movement actually helps reduce stress on the spine.
The research team developed a customized female musculoskeletal model with an articulated spine and sliding joints between the breasts and torso to enable breast motion. This innovative approach allowed them to simulate what happens inside the body during running with different types of bras.
The scientists used one female participant with a 34DD bra size as their test subject. They attached 59 markers to anatomical locations on her body and had her run over force platforms at a self-selected speed wearing three different breast support conditions: no bra, an everyday bra, and a sports bra.
How “Zero Bounce” Affects Your Spine During Exercise
The study included an “extreme” bra condition simulated during the modeling process. This hypothetical condition eliminated all breast motion relative to the torso, essentially creating a scenario where the breasts couldn’t move at all.
When the researchers eliminated breast motion entirely in their model while keeping the same running gait, they observed increased lumbar joint moments, which means greater stress on the lower spine. The difference wasn’t trivial either; the changes were greater than 0.05 Nm/kg, which previous research has associated with back pain.
In simpler terms, when the breasts couldn’t move at all, the spine took more strain. The study also revealed that wearing different bras changed how participants ran. Women in sports bras ran with their torsos about 4 degrees more upright than when running braless.
Challenging Sports Bra Marketing Claims
Sports bra manufacturers thrive on the long-emphasized claim of their products providing maximum support and bounce reduction. Brands frequently promote their products based on how much they minimize breast movement, with the assumption that less movement is always better.
While bra companies attribute this to improved design, and while reducing breast motion does help reduce pain, bras that severely restrict movement might have unforeseen consequences for the musculoskeletal system.
An optimal sports bra should reduce breast motion enough to prevent pain and discomfort but still allow some controlled movement to help distribute forces and reduce spinal loading and the risk of back pain. This should especially be top-of-mind for women with larger breasts, who often experience more movement-related discomfort during exercise.
So what does this mean for women who exercise? The study doesn’t suggest abandoning sports bras—quite the opposite. Appropriate support remains crucial for comfort and preventing breast pain during activity. However, we can now rethink the notion that the most restrictive bra is always the best choice. The next time you’re shopping for a sports bra, remember that some controlled movement might actually be good for your back.
Paper Summary
Methodology
The study used a subject-specific female musculoskeletal model with an articulated thoracolumbar spine and sliding joints between the breasts and torso. One female participant (bra size 34DD) had 59 markers attached to anatomical locations and ran over force platforms at a self-selected speed in three different breast support conditions: no bra, everyday bra, and sports bra. The researchers also created an “extreme” bra condition simulated during the modeling process by eliminating all breast motion relative to the torso. Two categories of simulations were run: 1) investigating how different breast support garments affect torso motion, breast forces, and spinal moments; and 2) examining how changes in torso motion affect breast forces and spinal moments.
Results
The researchers found that reducing breast motion relative to the torso (about 0.03 m) via a more supportive sports bra caused a reduced torso flexion angle (about 4 degrees) and an increase in peak extension spinal joint moments (about 0.15 Nm/kg) compared to running with no bra. When simulating an “extreme” bra that eliminated all breast motion relative to the torso but used identical experimental gait kinematics, the researchers observed increased peak lumbar extension moments (0.04 to 0.10 Nm/kg). The study suggests that bras designed to maximize bounce reduction may increase internal loading on the spine and possibly lead to back pain.
Limitations
The study acknowledges several limitations. First, it used only one participant and one trial in each condition, limiting its generalizability. The self-selected running speed varied between conditions, which may have influenced the results. The model did not account for musculature and the resulting muscle contraction forces on spinal joint compression and shear. Additionally, breast kinematics were captured using a marker placed on the bra, which may not perfectly reflect actual breast tissue movement if there was relative motion between the breast tissue and bra.
Funding/Disclosures
The paper states that the authors received no specific funding for this work and declares no conflicts of interest.
Publication Information
The study titled “Modelling Female Breast Motion During Running: Implications of Breast Support on the Spine” was conducted by researchers Chris Mills, Timothy A. Exell, Melissa E. A. Jones, and Joanna Wakefield-Scurr from the School of Sport, Health and Exercise Science at the University of Portsmouth, UK. It was published in the European Journal of Sport Science (2025, Volume 25, Article e12290) and is available as an open-access article.
