Breastfeeding and exercise, is it safe?

Research has shown that moderate exercise has no effect on a nursing mother’s milk supply, composition, or baby’s growth. Exercise supports breastfeeding by improving the new mom’s overall well being- physically, emotionally, mentally and socially.  Breastfeeding can deplete calcium stores and exercise increases bone density. As with any exercise program it is important to train smart with a strong foundation in place that supports our efforts towards success and is considerate of our current physical condition.

The Foundation:

Most new mothers do not resume their exercise programs until 6 weeks postpartum. This provides a window of opportunity to establish breastfeeding prior to reintroducing exercise. Starting slowly is necessary for the postnatal condition as the core is assessed through functional movements. Exercise is typically not high intensity at this time. Exercise will not undermine nursing. It can alleviate maternal frustrations by releasing endorphins- one of the body’s natural defenses against depression. Although high intensity exercise (to exhaustion) has been shown to have effects on breastmilk (see details below), these effects are short lived and not detrimental to nursing or the baby. Very few new mothers are exercising to exhaustion.

Breastfeeding requires an additional 500 calories per day. Moderate intensity exercise requires approximately 300 calories per 30 minutes. It is imperative that the nursing mother ensures she is intaking enough calories to support her activities and staying well hydrated. An average 10lb increase in body weight is normal until weaning has begun, usually within the first 12 months, so don’t be overly anxious to shed those last few pounds.

Here are the straight up answers to the FAQ’s:

Q: Will the baby reject the breast or milk after exercise?
A: No. The baby may dislike salty perspiration and the breast may be wiped clean with a cloth prior to being offered. A widely publicized study in 1992 suggested that babies reject breastmilk after exercise. These findings are considered questionable due to lack of controls in the study, including feeding the breastfed babies expressed milk in droppers. Subsequent studies have shown no difference in baby’s acceptance of breastmilk post exercise.

Q: Will lactic acid build up in breastmilk?
A: High intensity exercise has been shown to increase lactic acid in breastmilk, but it lasts only up to about 90 minutes post exercise and is not harmful to the baby. Moderate intensity exercise has shown no increase of lactic acid in breastmilk.

Q: Will exercise affect immunologic factors in milk?
A: Studies have shown that IgA levels are decreased 10-30 minutes after exhaustive exercise. The impact of this on a single feeding is negligible. Moderate intensity exercise has shown no effect of IgA levels in breastmilk.  Interestingly IgA levels increase after a breast has been emptied, regardless of exercise.

Q: Will exercise increase my chances of developing Mastitis? (clogged ducts)
A: No. When lifting upper weights choose compound exercises such as bicep curl to shoulder press to avoid overly repetitive singular movements.

Q: Are milk production and let down affected by exercise?
A: No. Consume the necessary nutrient dense calories to support activity and stay well hydrated. After exercise allow time for the heart rate to lower and the body to relax before nursing.

There are many factors that affect breastfeeding and milk supply and a lot of mothers find nursing challenging in some way. Exercise is in no way contraindicated and the benefits support the process. Training smart is always the imperative, and exercise IS secondary to the success of nurturing a newborn. If exercise is an unneeded stress it becomes counterproductive but breastfeeding is no reason to avoid exercise. I trained for a half marathon while nursing full time!

Here are some tips for training smart while nursing:

  1. Wear a very supportive Sports bra- the breasts are heavier when nursing.
  2. Be vigilant with adequate calories & hydration- this is essential so do the math!
  3. Balance rest and exercise. Sometimes exercise will pick you up when you feel low on energy, and sometimes you just need to take a nap! Make the fair judgement call.
  4. Have a program in place to structure your exercises accordingly. Avoid prone positions if they are uncomfortable. When lifting upper weights choose compound exercises to avoid repetitive movements.

Focus on postnatal recovery and getting strong rather than losing weight quickly. Approach exercise as an important aspect of your overall health which will ultimately support all of your ambitions, including successful breastfeeding.

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Kate Rita
Kate Rita is a certified Personal Trainer & Pre/Postnatal Specialist and a certified Pfilates instructor. Kate’s mandate is to help moms recover from pregnancy in a safe and effective way, incorporating fitness into the new normal for life.
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