Either way, check with your doctor. Some research indicates that exercising moms have a higher volume of breastmilk than sedentary moms so it is fine for breastfeeding moms to exercise. However, since you are expending calories through both exercise and breastfeeding it is crucial that you eat enough to meet those demands. Staying well hydrated will be important, since your fluid needs are increased by both lactation and exercise. To avoid excessive fatigue and maintain a good nutritional intake, it is also important to lose weight slowly while breastfeeding.
Some mothers find their infants are more 'fussy' with breastfeeding following a strenuous workout.
Increased lactic acid in breastmilk may be the reason. If this is your experience, it may be helpful to express a little milk before nursing your baby after an exercise session to remove the milk with the highest lactic acid content. Weight loss after delivery can be a very challenging and frustrating time for many women. Remember that it took approximately nine months to gain the weight so try not to expect it to disappear overnight. It is a slow process and you should aim to lose no more than one to two pounds per week.