Having looked at my Facebook and Google analytics I saw that 2/3 of visitors to my pages are female, so I decided to write a blog just for you!

As a male, I have no idea what it feels like to have large breasts and on top of that run with them! But having worked with many athletes, I know that it is a legitimate concern for many women. In researching this article, I found a stat that 34D breasts add 2 pounds of mass to the front of the chest! I have met plenty of clients over the years who have had breast reductions to help alleviate various forms of back pain. The significant relief following reduction suggests that larger breasts can affect spinal mechanics. Some other searching found that during running the breasts accelerate at anything between 2-12G, which if you combine with 2 pounds of mass as above is a large force! Knowing that the varying parts of the body are inter-related, I wanted to review how breast size and support can affect running mechanics?

A recent paper¹ found that in the 2012 London marathon, 1/3 of female participants experienced breast pain. The prevalence of pain increased with cup size, affecting 24% of athletes with ≤A cup size, and 51% with ≥F cup sizes. However, 44% of them took no measures to overcome the pain, including a well fitted sports bra. 17% of the female marathon participants said that breast pain affected their participation in exercise.

A recent PhD² paper found some interesting links between breast size and level of support provided by the bra. It found that high levels of breast support reduced breast pain in all types of recreational sports. It also found that it produced favorable changes in running biomechanics:

• Increased stride length and knee flexion during the swing phase which both cause a higher level of performance.
• Reduced trunk motion in a sagittal plane (see figure 1 below which shows this plane):
  • Ideally in running we want to have and maintain a gentle forward lean versus an upright poise. The forward lean moves our center of mass slightly ahead of our hips and allows us to better use our gluts. It also reduces our chances of over-striding, which provides a breaking effect.
  • The trunk is the structure that the legs are moving from. If there is excessive motion it will effects how the legs move and the force they can develop.

Figure 1: The sagittal plane of a runner. The trunk can flex/bend and extend/straighten about the axis going through this plane.

• Reduced trunk motion in a transverse plane (see figure 2 below which shows this plane):
  • When we run there should be a small amount of rotational movement through the trunk and pelvis. However when breast support is low there is a greater amount of trunk rotation from the inertia of the breast. This then leads to higher pelvic counter-rotation. To run efficiently means we want our energy to be predominantly moving us forward, however increased rotation means energy is being lost laterally.

Figure 2: The transverse plane of a runner. The trunk and pelvis will rotate in either direction about the axis going through this plane.

These benefits of high level of support are a good reason to make sure you are fitted well. If you are not well fitted, the inertia of the breast tissue will not only affect the mechanics of the body close to them (like the spine), but will also affect that further away (such as the knee). With poor support the odds are raised that you will try and alter the mechanics of your body to reduce the displacement of the breast to produce comfort, which may also cause issues with other mechanics elsewhere in the body.

Our friends at Fleet Feet Sports Huntsville have staff trained to fit you for a sports bra. Reduce your risk of injury, reduce your pain, and improve your performance today!

References:

1. Brown N, White J, Brasher A, Scurr J. The experience of breast pain (mastalgia) in female runners of the 2012 London Marathon and its effect on exercise behaviour. Br J Sports Med. 2014;48(4):320-5.
2. White, Jennifer L (2013) Breast support implications for female recreational athletes. PhD thesis, University of Portsmouth.