Does the composition of breastmilk change due to exercise?

[MoshiMoshi]

I have just been for my first run in three months and am now feeding my 5 week old DD. When I had DC1 I recall the wisdom on exercising when breastfeeding was that it was possible for lactic acid to be present in breastmilk if the mother worked out at a sufficiently high heart rate (ie presumably above the fat burning rate and more at the cardio enhancing rate). I have since heard that the ideas about lactic acid in breastmilk have changed and wondered if anybody could update me? Many thanks.

Recent studies have shown that frequent, sustained moderate to high intensity running do not impair quality or quantity of BM, or noticeably effect infant feeding behaviour, and there's little change in blood or milk lactate levels. Extremely intense interval training at an intensity that exceeds anaerobic threshold may occasionally increase lactic acid in milk, altering taste and infant acceptance of the breast immediately after a training session. So the cardio zone is thought to be fine, its the anaerobic range- max heart rates where may be some lactic acid in milk.

Enjoy your running!

Thanks, Maygirl. So I should only consider it if doing, say, a hard interval session when it would be advisable to feed or express beforehand if a feed is due immediately afterwards. I also read something about training increasing milk supply which sounds great!

Maybe have some ebm available, but try DD anyway, I don't think its harmful, just they might not like the taste!
I definately used to feel a rush of milk coming in driving home from the gym. Maybe its the getting hot, body must think baby needs more fluids too or something! Or because mammary glands evolved from sweat glands make more milk when you sweat??!!!

I started running again when DD1 was also 5 weeks old. She's now 12 weeks and I'm up to 25 miles a week, as well as cycling about 50 miles (I've been a club runner for many years). I (foolishly!) entered a half marathon for July when I was pregnant (seemed like a good idea at the time!), so I am needing to get out for increasingly longer runs.
I always make sure both barrels are empty before I go (DD satisfied and more comfortable for me!). On the occasions DD won't empty me, I express and either freeze it for future use, or put it in the fridge for DH to give to her whilst I'm out.
We are lucky that DD is not fused where her feed (or from whom) comes from, but we did introduce this after about 3 weeks, and give her EBM several times a week.
I've found that BF can leave you with less energy for hard running. I've decided not to rush back into hard interval training, to just enjoy the precious 'me time' that running offers, and my DD gummy grin when I get home. There's plenty of time to run hard after I've finished BF.
Good luck, and enjoy the glorious weather! x

Thanks, runragged! In all likelihood, my intervals won't be very hardcore for some time as all my running involves a buggy with multiple children on board so the lactate levels will be academic. I took my time getting back into training after DC1, but I am 6 years older and my body 4 children later so needs must, and I actually do want to get out there as I am chomping at the bit with all this lovely weather! I see you cycle too! Do you do duathlons/triathlons? My turbo trainer has been packed away as we have builders in but I am also looking forward to getting back on the bike!

Oops, sorry. Make that "runnerragged"!

Think has to do with the production of lactic acid, but am fairly sure the rush lasts only for a short period -- like 30 minutes...

Envy your ability to go the distance!

Respect to you MoshiMoshi - 4 of them! Hope you didn't feel I was patronising you - I'm still learning my trade unlike you!
I did join a tri club last year but it was just before I got pregnant so I never actually got to do a triathlon. Now I don't know when I would ever have the time to train for it! Cycling seems to stop me from getting injured though. I used my turbo trainer when I was pregnant until my bump got in the way! Weather is too nice to use it at the moment though. Good luck MoshiMoshi x