What is the effect of weightlifting on pectus excavatum?

May help sometimes: There is an article called "exercise therapy in the correction of pectus excavatum" by steward cheung (in hong kong) that describes the stretching and types of exercises than makes the pectoralis muscles pull outward on the breastbone (sternum). It is very hard to consistently do exercises several times a day, but if one does them, the exercises may help the pectus excavatum look better.

Unlikely: Pectus excavatum is a posterior deformity of the breast bone. It grows toward the spine causing a sunken appearance to the chest. Exercising can increase the pects and other chest muscles, but cannot reverse the tendency of growth of the breast bone and ribs.

None: Muscular development does not impact the cartilage deformity of pectus excavatum, except in the case where the muscles may mask the skeletal deformity somewhat (not very effectively).