We have mentioned , in comparing plants to animals, that exercise is exclusively required by all animals because only animals have hearts and able to perform movements. 

What then heart and exercise have to do with movement?

We have mentioned that circulation of blood, lymph, and other bodily fluids, such as urine and intestinal contents, depends solely on muscular tissue to move them around.  The heart is a specialized muscular organ that differs from the skeletal muscles it its ability to contract without our will and to adapt to changes in a vast range of variables.  The skeletal muscles augment the heart, big time.

Therefore, just sitting there and expecting the heart to do the whole job without our engagement in regular exercise would result in the widely spread wasting or muscles, ailing of the blood vessels, and the rest of the body systems would follow in suffering, one after the other.  

1) Cells will ail because lack of necessary nutrients, or over accumulation of metabolites.

2) Muscles will ail because the very elements of the muscles are cells that are ailing.

3) Cellular products will accumulate in improper sites: blocking the conducting channels: blood vessels, and lymphatic.

4) Bones will ail because both their cells and the muscles acting on them are ailing.

5) Blood vessels lose their vigor of contractions to mobilize blood, lose their channel space to accommodate flow of blood, and lose their vitality in delivering and retaking products to and from the cells.

6) Heart loses its vital cells as well as its ability to deal with ailing clogged, rigid blood vessels to deliver blood flow.

7) The nervous system is the most sensitive system to ailing muscular well being. Accumulation of unnecessary cellular byproducts as a result of inefficient muscular function impairs the ravenous needs of energy by the nervous system.