Certain exercises help ruduce the pectus excavatum?

Depends: It depends on the edxtent of the defect. Certain excercises can increase chest muscle mass such as the pecs. This may also accentuate the defect. There are no excerceses that can remodel the chest/rib cage.

Pectus excavatum: Pectus excavatum can be surgically repaired, but surgery is usually reserved for people who have moderate to severe signs and symptoms. People who have mild signs and symptoms may be helped by physical therapy. Certain exercises can improve posture and increase the degree to which the chest can expand. http://www.mayoclinic.org/diseases-conditions/pectus-excavatum/basics/treatment/con-20028599