Is Breastfeeding Slowing Me Down? Lactation and Competitive Running

Nursing the baby before an 18:30 5k.
Nursing the baby before an 18:30 5k.

Is breastfeeding slowing me down?

To be clear, the benefits of breastfeeding for my son and me outweigh any short term negative impact on my speed. Fortunately my livelihood does not depend upon running so I am free to make that choice.

Running is a key component of my lifestyle, however, and I have lofty personal goals! I’ve been sitting on a plateau of essentially identical 5k and 10k times from 4-14 months postpartum and I’m beginning to doubt my more ambitious goals. I’m pretty confident in saying that lactation is not performance-enhancing, but how much, if at all, does it hold me back?

First, I’ve learned that testosterone levels decrease during lactation. Although T in women is significantly less than in men (30 to 95 nanograms per deciliter range versus 300 to 1,200 ng/dL), it is still an essential hormone. Unfortunately I could not find specific T levels associated with lactation (and certainly not in a population of athletes) so I can only speculate about the magnitude of effects.

But we know that testosterone is related to physical ability, energy levels, and aggression so it would follow that this decrease could tack on time to your races. In addition, testosterone may assist in coping with pain (hello marathon training!).ย  The decreased T levels along with increased prolactin (the hormone that helps moms produce milk) are associated with a lower libido. Pepper thinks this is bad for your race times!

On the positive side, women who breastfeed have better bone density. Yes, even though you are producing calcium-rich milk, your calcium absorption is increased so a runner who has breastfed may be less likely to get stress fractures! Another bit of good news is that by inhibiting menstruation, your iron stores are conserved. The amount of iron produced in breastmilk is far less than what would be lost through monthly periods. And you’ll also miss out on all the monthly yuckiness that tags along.

I would be remiss if I didn’t mention lingering effects of pregnancy–such as increased blood volume–which can boost performance. I’ve spoken with many mothers and read anecdotes from others who report an increase in pain tolerance after labor and delivery. Many women end up running their fastest times after giving birth! I am just itching to join that club.

Some nursing moms report losing weight quickly while others believe that breastfeeding seems to make them hold on to a few extra pounds. A few pounds up may slow you down slightly, but being underweight has its own risks (including your milk supply). Personally, I am within a couple pounds of pre-pregnancy weight but my diet is whacked out! I waver erratically (often within the same day!) between a focus on high quality vegetables and protein and a severe craving for all the chocolate. I’ve also suffered dehydration from underestimating my increased fluid needs. Higher calorie and fluid needs add an additional challenge especially to marathon racing.

When JB was tiny, long runs were significantly limited due to his 2-hour interval between feedings, unless I wanted to pump an extra bottle and get through the discomfort of full boobs at the end of the run. Of course this was a very temporary inconvenience and introducing solid foods at 6 months reduced the pressure of being his exclusive source of nutrition. And–bonus!–Patrick bought me a new Garmin to celebrate the milestone!

On the other hand, a break from training, lingering pelvic or back issues, and loss of core strength will hold you back, at least temporarily. A word of advice here–don’t delay a visit to a women’s health physical therapist for an evaluation. Thyroid problems may emerge in the postpartum period. In addition, relaxin–that joint-loosening hormone–may stick with a nursing mama longer.

Finally, having a newborn causes some significant lifestyle changes regardless of whether you are breastfeeding (or whether you are the one that gave birth). Lack of sleep, an altered training schedule, use of a stroller or treadmill, and changing priorities are a few factors here. JB and his daycare buddies have shared a variety of illnesses with me that have interrupted training on several occasions. I have yet to exceed ~80% of pre-pregnancy mileage and I complete the vast majority of those miles on the treadmill. Oh–and we still don’t sleep through the night!

So even though there isn’t any hard evidence that breastfeeding is slowing me down, it’s really no surprise I’m slower right now. But I have hope that as weaning, maturation (please sleep, kiddo!), and adaptation to my new lifestyle continue that I will be able to chase the Olympic Trials marathon standard. I don’t have a deadline on breastfeeding, and I also don’t have a deadline for this goal–but 2016 would be nice.

OK, mamas, time to weigh in: Did you nurse while competing? Did your races times improve with weaning? When did you set your PRs?

I'm a 20-year veteran of competitive running, USATF certified coach, mom of a toddler -- and still trying to set PRs. I write about training from 5k to marathon, motherhood and competitive running, and the elite side of the sport. The 5k is my favorite race (16:56 PR) but I've got a score to settle with the marathon.

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  1. Great post, thank you for sharing! I feel like you are my running/pace twin and I hope to be there on the start line with you at the 2016 Trials (and beyond!).
    Yes, breastfeeding is awesome and I’m one of those ladies who has run all my PRs except 5k while breastfeeding! I was still fairly heavily (2-4x/day) breastfeeding when I ran 1:15:59 at RnR NOLA in January. Then you know my marathon story… quickly weaned to 1x/day before the race and had a horrible DNF experience. Felt like poo from beginning. A new piece of info is that I got my first postpartum period 2 weeks after that bad race so the hormones were definitely going wild on race day!
    I have also weaned my little guy since my bad race (having nothing to do with racing. He was 18.5 months old and it seemed like a good time). Now I have the rest of 2015 to see how the weaning vs running fast equation works as I’m going for that standard!
    I feel you on catching every sickness and not sleeping. My baby just started sleeping an 8 hour chunk last week! He was a great little tiny baby sleeper, but starting at 10 months he had me up at least 2-3x/week every night.
    In conclusion, I have nothing novel to say but I’m happy to be working through this with you!

    1. Hi Jen! First, it was so nice to see you on Sunday!! (I would say “meet” but I feel like I already know you through the internet…:) )
      You experience has been so interesting to me and completely INSPIRING! Super interesting that your period came back right after that race. I imagine that was wholly to blame for the bad day, ugh.
      We’ve done so many of the same races, but I don’t think ever at the same time! Maybe LA will be the first!!

  2. Great article…I am 8 months post partum and running quick speeds with and without stroller. Have set some PRs but def have the good and bad days. Carrying some extra lbs still which I think is bc of breastfeeding but 100% x1000 worth it for baby!!! ๐Ÿ™‚ Love your blogs.

    1. Hi Allison! Congrats on your PRs…and only 8 months PP! Holy cow! Yeah, a couple extra pounds are no big deal at all, definitely better than being underweight for everyone involved. Keep me updated on your progress. I imagine you’re going to continue to shave time off your races!

  3. First, I LOVE that photo! Second, I don’t know where to start! I’ve been nursing and/or pregnant for so long (just stopped almost a month ago, finally!) that I don’t know any more what’s happening to my body from nursing, what’s from the pregnancies in close proximity, what’s from aging and what’s from anything else. After my first baby, I got back into prepregnancy shape relatively quickly – I basically matched my PRs from 5k – half marathon around 6 months postpartum. My son was a terrible sleeper (still is, actually) and nursed all night (coslept for sanity purposes). I struggled once I started to marathon train for a race about 10 months postpartum. Longer workouts zapped me and I ended up DNFing the race because I felt so horrible. I got pregnant a couple of days later so I can’t really say much beyond that. It took me longer to get back into things after my second baby (born 19 months after the first). Instead of 6 months it took me about 9 to get back to where I left off. I ended up getting into the best shape I have ever been in but started to experience what I now know is burn out from overtraining during that time. I don’t know if the overtraining was because I was training too hard while nursing or training too hard period. Maybe both. I got pregnant during an injury lay-off when my second was 20 months and I have not been able to string together much since having my third. My body is just very cranky. I feel slightly better since I stopped nursing, but that could be a coincidence. Who knows. I have noticed my libido is improving a little in that I have an inkling of one now and had about zero a month ago ๐Ÿ˜‰ So, I suspect my T levels are improving. I hope!

    In the end though, I wouldn’t change anything! Even if I never run faster, I will look back fondly on my years as a nursing mom. My kids are only babies once and I have a lifetime to be an athlete and enjoy this sport. So I suppose, breastfeeding, while probably inhibiting my improvement as a runner, helped me put running in perspective.

    1. Thanks, Salty! I was glad I made Patrick take this photo (& I have a couple more pre-race nursing photos as well – one sitting on a curb). Funny thing, I had pinned my bib on ahead of time (patting myself on the back for being prepared) but then had to remove it since it was completely in JB’s face. That would have made a good photo opp!

      There’s definitely so many variables involved in being a running mom! The sleep thing is huge. And sleep deprivation makes all the little daily things so challenging/stressful that running can really put us over the edge. I’m not sure how you do it with 3x the kids!

      If I could re-do things, I don’t know if I’d try to run a marathon in the year PP or focus on shorter races or just relax with the running thing for a bit. Your assessment in your last paragraph is spot-on though – the choices I made for the baby were good, at least!

  4. I couldn’t run more than 5-6 miles at a time while breastfeeding. Most runs needed to be cut at 3 miles. I would just get so dehydrated and my supply would go down severely whenever I tried to add more miles to the routine. I didn’t race much until recently, so I don’t know if I still could’ve had a 5k pr. But I do know I kept a pretty good clip (thanks to my trusty timex) while on my daily run–faster than I am now at least.

    1. Hi Erin! Thank you for sharing your experiences. That sounds really tough! Good reminder that each body is so different – good for you for paying attention and knowing your limits.

  5. I am currently breastfeeding my six month old and he is my 5th child. My fastest times and PR’s were a year after I had my twins (they were before my 5th child and they will be five next month) and I was still nursing them (not as much, though, maybe 3-4 times a day). After I weaned them, I hit my lowest weight point and I was the fittest I have ever been. I definitely believe that I am one of those woman who hold on to a few pounds while breastfeeding. I am still about 10 lbs off of where I would like to be. I know it won’t come off until I am done. This postpartum recovery has been so hard for me. It’s really just because of life circumstance – I have five kids, I am working full time, I will be 40 next month, and I am just feeling my age!!! It has been much harder getting back into shape and back into running. For measure, 6 months after having my twins I placed in my age group at a local 5k with a pretty decent time. Currently, 6 months postpartum now, I know I couldn’t put up those same numbers if I had a fire under me. I plan to at least nurse my little one for a year, but will most likely go longer. I just love it too much and I have no race goals on the horizon. I would like to run the Columbus Marathon this October and BQ, but I had a pretty serious injury right before I got pregnant (a pelvic stress fracture) that taught me a valuable lesson about listening to my body. I am just happy to be able to run, and to be able to participate in some races. I am not gunning for any PR’s anytime soon. I do notice, though, that after my runs this time around I am STARVING! Ravenous. Like I cannot shovel enough food in my face fast enough. Even after just five miles. And I do eat something about a 1/2 hour before I go out. I think as you age, hormones get more and more whacked out. I don’t remember ever being so hungry after a run with my others. I have never nursed and trained for a marathon before, so it will be interesting to see how I do. I did notice the past few weeks that with slowly moving up my mileage (I was running 5-10 miles a week and I am now up to 20 miles a week), that my production is off by a few ounces. It’s fine since I was able to freeze a ton of milk, though.

    1. Hi Michelle! Congrats on your little one. You are definitely a busy lady!!!! You bring up another interesting point – age! Adding up pregnancy and recovery from birth time, we’re 1-2 years older.

      The hunger can be hard, can’t it? Sometimes all I can do is eat a bunch of chocolate. I think my body just needs a crap ton of calories and that’s the most efficient way to do it! ๐Ÿ˜‰

      Good luck with your comeback! If you do Columbus, we should meet up!

  6. Thank you so much for this – I am still nursing my 17mo old, and hitting great workouts, and only mediocre races. I am hoping that sleeping through the night could change this and I could join THAT club you talk about!

    1. Hi Em! Congrats on making it to 17 months! I am the same way with good workouts/lackluster races! I wonder if others have experienced that, too. I’ve wondered if it’s because I now pick & choose when I feel good enough to do a workout, but I don’t have that kind of control with races.

      Let me know WHEN (not if) you join that postpartum PR club & what factors got you there.

  7. Just came to this post after seeing you mention it in your post today. I’ve never thought of the possibility of breastfeeding affecting my running. I started running after my 2nd baby was born and have been breastfeeding or pregnant with no break in between since. I guess I have a new thing to blame for being slow now, lol. “I’m not really this slow, it’s just because I’m breastfeeding.” ๐Ÿ™‚