Hi Mam... You can certainly do mild to moderate exercise during lactation.. Research shows that moderate exercise doesn’t affect milk supply, milk composition, or baby’s growth. For your own comfort, you may wish to nurse before exercising and wear a good, supportive bra. Some babies object to breastfeeding after mom has been sweating due to the salt on mom’s skin. You may wish to take a shower before nursing. If you regularly lift weights or do other exercise involving repetitive arm movement and you develop plugged ducts, cut back and start again more slowly. Keep yourself hydrated.