Running and Breastfeeding: Mastitis

Breastfeeding symbol
Boobs: not just for being smushed by sports bras! (Photo credit: Wikipedia)

About a year ago, Salty wrote a information-laden post about breastfeeding and training: Got Milk? Running and Breastfeeding . Since that post appeared, I’ve had my own baby and have been exclusively breastfeeding for the past three months, which has brought me back to reading this post several times. I want to ensure that my milk supply and quality are not being affected by my desire to train for a half marathon. Being a first time mom, and grasping for any and all advice that’s out there, Salty’s post gave me the confidence that I could continue to train at a moderate level without affecting my milk supply or milk quality.

Recently, I experienced something related to running and breastfeeding that Salty didn’t cover: mastitis. Mastitis is an infection in a milk duct and it is one giant literal pain in the boob! I know I’m not the only nursing running mom to experience this so I thought I’d share what I’ve learned about running and mastitis. 

Most weekdays, I’m able to run between 2 and 5 miles in the wee hours of the morning, right after nursing my 3 month-old Connor and making sure my breasts are as empty as they can be for comfort. On weekends, when my husband can help with baby duty, I’ve been able to get in my longer training runs for the half marathon. So far, so good, but there have certainly been bumps in the road along the way, which brings me to the reason for this post: MASTITIS.  About 20 percent of breastfeeding women experience it, and I’ve been unlucky enough to experience it twice in the past three months. And I’ve come to wonder, what’s the connection between running and mastitis?

What is Mastitis?



English: Drawing of a cross section of the bre...
Mastitis is an infection in one of the ducts of the breast. (Photo credit: Wikipedia)

According to Mayo Clinic, mastitis is “an infection of the breast tissue that results in breast pain, swelling, warmth, and redness of the breast.” Fever, chills and flu-like symptoms tend to come along with it as well as fatigue. Mastitis is most common in breastfeeding moms in the first 3 months postpartum, and it tends to only affect one breast at a time.  Both times I’ve been afflicted, it has come on pretty fast and I’ve had a fever of 102 degrees. It’s tough to continue nursing as the pain is somewhat horrific, but continuing to nurse is usually what relieves the infection as the baby drains the milk from the breast. It’s perfectly okay to continue nursing with mastitis because it cannot be passed along to the baby.

Causes of Mastitis

Looking at the causes of mastitis is where we find the connection to running.

Blocked milk ducts. If you are not emptying your breasts at each feeding, one of your milk ducts could become clogged and cause milk to get backed up, leading to infection. If you are rushing to get your run in before your husband leaves for work and don’t let baby feed for a full 20-30 minutes (guilty!), this could lead to the beginning stages of a clogged duct. If you are re-entering the workforce after maternity leave and squeezing in pump sessions between meetings and phone calls (guilty!), this could also lead to infection. My sister, who is a pediatrician, explained it as milk becoming clogged and actually turning to a cottage cheesy ( I know, gross!) consistency. Immediate heat compression can melt this blockage and stop it from turning into a nasty infection.

Bacteria entering the breast.

According to Mayo Clinic, bacteria from your skin (perhaps from sweaty sports bras) and baby’s mouth can enter the milk ducts through a break or crack in the nipple. The bacteria can then multiply and lead to mastitis.

Oversupply of milk.

Another of my mom running friends mentioned that she felt as though her milk supply increased the more that she ran.  Simply put, the nipples are somewhat stimulated when breasts bounce when running and this causes a sensation as if the baby is sucking, leading to more milk production.  Someone else suggested making sure to breastfeed right before and right after my runs to help with this problem.

Restrictive bras.

Doubling up on sports bras has become a necessity while breastfeeding. But is the extra support leading to mastitis?
Doubling up on sports bras has become a necessity while running lately, but when I get home I whip ’em off and free the boobs!

My husband got me thinking the other day when he asked if I thought that wearing tight sports bras might be causing the clogs. When I’m getting my longer training runs in, I can have these on for upwards of 90 minutes. When I asked my OBGYN, she didn’t seem to think the two were related. When I asked fellow running mamas (one of which is a nurse practitioner in the OBYN wing), they seemed to think it might be. A little internet research seems to indicate bras that put a lot of pressure on the boobs and can contribute to mastitis. To be on the safe side, be sure to take off your sports bras when you do not need them on. I mean, get home from your long run and whip that sucker off and free the boobs! Salty herself had problems with mastitis until she stopped wearing bras at home. Coincidence? Probably not!


When you get mastitis, it’s like getting hit with a bad flu – there’s no training through this one. You will need to take time off while you nurse your own feverish self. If you suspect you have mastitis (a painful spot or lump in your breast coinciding with a fever), call your doctor immediately so you can get antibiotics. While you wait for those antibiotics to kick in hang out in bed with baby and let her nurse anytime she wants, because the nursing will actually help you and won’t hurt her. Once your fever is gone and you feel better you can cautiously resume running, but if your sore spot does not improve or you start feeling bad again…stop! It’s also important to hydrate, hydrate, hydrate. You can also massage the tender area and apply warm compresses until it feels better.

Have you experienced mastitis? How did it impact your training? What seemed to cause it for you? 

Remember that I am not a doctor or a health care professional. If you have any questions about your own health or that of your baby’s, contact your doctor or pediatrician!

I'm a new momma, full-time non-profiter, and coffee lover. I write about healthy body image, half marathon training, and recovery from eating disorders. I'm currently training to maintain fitness throughout the winter and break 1:27:00 in my next half marathon.

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  1. I had mastitis twice – about 4 months after my first and the same time after my second. The first time convinced me to make sure I took my running bras off when not running and to ideally go braless as much as possible! It’s so horrible to have. I got it about 3 weeks after returning to work. I was pumping throughout most days, but that day I took off from work. I had a busy day and didn’t pump and wore a sports bra all day. By the afternoon I noticed a hard sore spot on my breast. By the evening, I was sick as a dog! I think the combination of stress, not draining the breasts and compressing them doomed me. The only nice thing about it is the cuddle time with baby – it’s nice to not feel guilty about laying in bed all day snuggling and watching America’s Next Top Model marathons! The good news is it just takes a day or two of rest and antibiotics to be back up and running.

  2. So sorry you’re dealing with this! Thanks for using your experience to help others, at least! I, too, am doubling the sportsbras. I use an old flimsy one as the inner layer and then a tighter one on top. That way, even if I’m meeting friends to run or I’m at a race, I can at least strip off the constrictive layer without getting completely topless in a random parking lot. Or I can pump/nurse right before a race by lifting up the flimsy bra and then putting the good one on when it’s time to run.

    I’ve also noticed that running can increase milk supply! My theory is that it might also have something to do with heat — when mamas sense warmer temps, we make more milk to help quench baby’s increased thirst. Whatever the reason, I appreciate having the surplus to freeze. 🙂

  3. The more runner mamas that I talk to, the more I hear about other mastitis stories! It all comes back to a few culprits: stress, not emptying the breasts sufficiently, fatigue and compression! Both times, I wake up in the middle of the night with a really quick on-set – I’m beginning to think it may have to do with the fact that Connor is sleeping through most nights from 8 pm. to 5 am and I’m still producing enough milk to feed every 2-3 hours, leading to engorgement. I’ve been setting my alarm around midnight to pump but I also know that over pumping will lead to more milk production…a double-edged sword! With running the Columbus half marathon in 1 1/2 weeks, I’m worried about running for a good 90+ minutes with a tight sports bra (or 2!) on top of the corral waiting time and finish line celebration/walk to the car…I’m thinking I’ll be wearing that sucker for a good 4 hours…and I’m worried this will lead to another bout! Anyone out there have advice on this?

  4. I had mastitis twice (at two weeks and again at four). It was terrible and I wouldn’t wish it on anyone. The sad irony for me was that my milk supply was terrible and low and I was never able to exclusively breastfeed because of it, yet I still got mastitis. Lucky me! I wasn’t training at that point, so it had no affect on me in that regard, though.

  5. You can usually try to treat symptoms at home for about 24 hours before calling your doc. Frequent feeding and nursing on the sore breast, heating pads, expressing milk in the shower can help. Some moms who experience repeated episodes of mastitis have luck taking lecithin. Many moms experience oversupply in the early months and your risk of getting mastitis will drop as your supply evens out.

  6. And, you can definitely run, run, run while nursing! I read a blog post a while back about a mom who was still nursing one year old twins and ran a 100 mile race! She had a friend pump for her at aid stations! Our bodies are amazing!

  7. I may have to try the lecithin idea as well as the flimsy sports bra underneath the tighter one – thank you all!! I’m hopeful that my milk supply will even out and lessen within the next several weeks.

  8. Ugh, I had mastitis with my first and it was brutal! I’m sure the combo of the double sports bra and sweat are a lethal combination for those poor ducts. Cabbage leaves in the bra are super helpful for alleviating the pain. I’ve also found that I have way fewer clogged ducts now that I’m only nursing my second and no longer pumping – but when I did get a clogged duct, a hot compress and hungry baby were the best panacea.

  9. Thank you so much for posting this! I’m 13 months pp and am on my FIFTH bout of mastitis. I have been marathon training, and have wondered if this has anything to do with my frequent clogged ducts.

    1. Oh my goodness, Jennie! FIFTH bout?!?! I give you major props for sticking through the pain and discomfort to continue on breastfeeding. I’ve been lucky enough to have contained mine to the two series mentioned in the article; my supply eventually evened out and though I’ve dealt with a few plugged ducts since, I haven’t had full-on mastitis again. Hoping you don’t have to deal with this anymore!

  10. ahh!! So happy to hear I’m not the only one!! I have to wear extremely loose nursing bras otherwise I end up with a clogged duct(s). I’m still nursing my 13 mo and recently started working out. I went shopping for work out clothes today and my boobs didn’t seem to fit in any of the tops…they are all meant to be worn with tight sports bras and then fear set in!! I might do as suggested above and wear it only for my work out! Also, I thought I would add that massaging in a warm epsom salt bath always seems to do the trick for me on top of frequent nursings. Anyway, don’t understand how docs don’t see the correlation!

  11. I think that there is a definite link. I ran an ultramarathon on Saturday (100km) and expressed throughout, but not 100% as manual pump and my tatas don’t go together. On Wednesday I got a hotspot and felt terrible, luckily I had a dose of antibiotics in the house, as by Thursday early hours it was full blown mastitis. I think there is a definite correlation between the sports bra and the infection. I could have put money on the fact that I would get it.

    I am feeling better today (Saturday) but still have shivers and headache and although fever is gone, I have lumps so I know that the blockage has not cleared 100%.

    I won’t be running until it clears…. hopefully by Monday.

  12. I’m so happy I came across this! I have a problem with this as I marathon train. Glad I’m not the only one dealing with this issue! I’ve had minor cases that leave me a little achey and a sore boob, but finally had a more severe case that left me with a fever. I usually take some Motrin, chug water, nurse and hot towels on the affected boob and it usually passes in a 24 hour period.

  13. So happy I found this article. I just had my baby about 2 months , and now I started to work-out< its been two weeks since I start , and guess what I got mastitis . I had a feeling it was from the tight sport bra and my sweating. Am currently on antibiotics now and hope i get better.

  14. I’ve noticed a correlation, too. Did not have any problem with mastitis until the last few months, but since I started running, I’ve had four! I’m going to try freeing the Tata’s after my runs to see if that helps. Thanks for the info, everyone!

  15. I’m a first time mother who starting exercising again at around 7 weeks. I’ve currently got my first bout of mastitis and there’s no doubt in my mind it was caused by my tight sports bra a few days ago – I stayed in it too long after exercising and also ended up engorged because of a missed feed.
    I was dead keen to get back into running and half marathon training again, but I realise now that I’m going to have to be careful! It’s good to read about other people’s experiences!