Exercise and breastfeeding

Can I work out if I am a breastfeeding mother?

Exercise is good for everyone and breastfeeding mothers can work out, but they need to ensure they don’t lose too much water or too many electrolytes such as sodium and chloride (salt). Depending on how strenuously they exercise, it may help to drink electrolyte solutions before, during, and after exercise. Dark urine can be a sign that they need to drink more water. There is no evidence that exercise will harm babies or interfere with breastfeeding. Babies are nearly always happy to breastfeed after their mothers exercise.

A) Describing water and electrolyte loss

Electrolytes are charged atoms or molecules needed for the normal function of the body. They include: sodium, chloride, potassium, magnesium, and calcium. Electrolytes and water are lost from the body when mothers make milk, sweat, and with urination and bowel movements.

Athletes lose additional water and electrolytes through sweat during exercise. Sodium and chloride (salt) are lost in the largest amounts. If these are not replaced, the recovery from exercise can be slower and with extreme losses, the body cannot function properly. 

Electrolyte solutions may be helpful if mothers exercise very strenuously, for more than one hour, or are in a hot environment (Bailowitz et al. 2017). Other mothers can simply drink water. 

B) Breastfeeding and exercise

Exercise is very important for an individual’s mental and physical health. Regular activities such as resistance and weight-bearing training can prevent bone loss that occurs with breastfeeding (Ebina 2020; Lee 2020).

1) Before and during exercise

Mothers may find that they are more comfortable if they breastfeed or express just before exercising to minimize the amount of milk in their breasts. Bras with good support are very helpful.  

Breastfeeding mothers who exercise very strenuously should ensure they prevent excess losses of water and electrolytes. To do that, mothers may need to drink electrolyte solutions before, during, and after exercise and monitor their levels during exercise. Dark urine is a sign the body is working hard to hold onto water and mothers may need to drink more (McKenzie 2017). 

2) Breastfeeding after exercise

There is no evidence that babies are harmed by mothers who exercise vigorously or that it interferes with breastfeeding (Be'er 2020). Strenuous exercise will temporarily increase the amount of lactic acid in breast milk but this does not appear to keep babies from breastfeeding (Carey 1997; Wright 2002).


Bailowitz Z, Grams R 2nd, Teeple D, et al. Exercise-Associated Hyponatremia in a Lactating Female. Clin J Sport Med. 2017 Jul;27(4):e55-e57

Be'er M, Mandel D, Yelak A, et al. The Effect of Physical Activity on Human Milk Macronutrient Content and Its Volume. Breastfeed Med. 2020 Apr 8

Carey GB, Quinn TJ, Goodwin SE. Breast milk composition after exercise of different intensities. J Hum Lact. 1997 Jun;13(2):115-20

Ebina A, Sawa R, Kondo Y, et al. Daily physical activity is associated with increased sonographically measured bone status during lactation. Womens Health (Lond). 2020 Jan-Dec;16:1745506519900582

Lee LL, Huang SF, Lai PC, et al. Effect of exercise on slowing breastfeeding-induced bone loss: A meta-analysis and trial sequential analysis. J Obstet Gynaecol Res. 2020 Jul 8 

McKenzie AL, Armstrong LE. Monitoring Body Water Balance in Pregnant and Nursing Women: The Validity of Urine Color. Ann Nutr Metab. 2017;70 Suppl 1:18-22
Wright KS, Quinn TJ, Carey GB. Infant acceptance of breast milk after maternal exercise. Pediatrics. 2002 Apr;109(4):585-9