Moderate exercise has a benefit for health and it is entirely suitable while breastfeeding. It does not affect composition of milk nor diminishes the amount produced, instead, it may be increased. Exhaustive exercise could decrease IgA and lactose secretion, and, increase lactic acid and protein content, which can alter milk flavor though well tolerated by the child. A continuos and intensive exercise would be advisable only for women who have undergone previous training, for instance professional sport women.