Well generally it will be a positive impact (Of course this generally depends on what the "Physical activity" is, it is generally good, reason being while exercising causes the brain to release endorphin's, as well as helping relax muscles and relieve physical tension, which can greatly help with stress.
Diseases or other disorders can be passed down through your family so you need to know your families history to know if you are at an increased risk.
By contracting, muscles pull on bones and allow the body to move.
