Understanding the relationship between cardiorespiratory endurance training and other categories of conditioning requires a review of changes that occur with increased aerobic, or anaerobic capacity. As aerobic/anaerobic capacity increases, general metabolism rises, muscle metabolism is enhanced, hemoglobin rises, buffers in the bloodstream increase, venous return is improved, stroke volume is improved, and the blood bed becomes more able to adapt readily to varying demands. Each of these results of cardiovascular fitness/cardiorespiratory conditioning will have a direct positive effect on muscular endurance, and an indirect effect on strength and flexibility.
Congenital heart defects. Congenital heart defects are heart problems that babies have at birth. Congenital heart defects occur while a baby is developing in the mother's uterus. Doctors don't always know why congenital heart defects occur — some congenital heart defects are caused by genetic disorders, but most are not. A common sign of a congenital heart defect is a heart murmur . A heart murmur is an abnormal sound (like a blowing or whooshing sound) that's heard when listening to the heart. Lots of kids and teens have heart murmurs, which can be caused by congenital heart defects or other heart conditions.