Lactation, Breastfeeding, and Competitive Running

Originally posted by Catnip in 2015

Do lactation and breastfeeding slow us down?

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

Running is a key component of my lifestyle, however, and I have lofty personal goals! I sat on a plateau of essentially identical 5k and 10k times from 4-14 months postpartum and began 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 us 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!). 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!

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 quickly got within a couple pounds of pre-pregnancy weight but my diet was whacked out for a while! I wavered erratically (often within the same day!) between a focus on high quality vegetables and protein and a severe craving for all the chocolate. I also suffered dehydration from underestimating my increased fluid needs. Higher calorie and fluid needs add an additional challenge especially to marathon and ultra-distance racing.

When my son 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.

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. Your baby and his daycare buddies will share a variety of illnesses with you that can interrupt your training. When JB was a baby, I did most of my miles on the treadmill and it took ages to get back to pre-pregnancy mileage. Oh – and did I mention the lack of sleep?

So even though there isn’t any hard evidence that breastfeeding slows us down, it’s really no surprise I that was slower while breastfeeding.

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

Sal is a 4 year old 77 hour trail marathoner looking to whittle a few minutes off next time. Being a gastropod, Sal is neither male nor female but will accept either set of pronouns. Sal's spirit animal is the cheetah and Sal's mantra is, "What's slow to some is fast for others." Sal writes about Salty Running news.

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  1. Great article. I’m about 6 mo out from weaning my son (he’s my first). While i was nursing him, I was able to race, but wasn’t nearly as fast as my PR time, and i did hold on to about 5lb extra weight while nursing. I had also never night weaned him, so i was still getting up at least once per night. We weaned cold turkey one long weekend when he was about 14mo, and other than a little bit of weepyness at first, i haven’t turned back. I’ve since set 2 new BIG PRs and with sleeping through the night (most of the time) getting up extra early to run before work has been great. So yes…it seems like nursing affected my performance, whether it was due to hormones or lack of sleep (likely both) I have gotten considerably faster since weaning.

  2. I ran while nursing both my kids – long runs were always a juggle! I did my first post partum half around 4-5 months each time which meant pumping and being gone a half day. I don’t think it impacted my training or racing any more than just the regular recovery from pregnancy.

  3. I’m still nursing and just ran a Marathon PR a few weeks ago (by about 10 seconds). I thought my supply would drop, but I’ve been able to EBF. He’s now almost a year old. ๐Ÿ™‚