<span>Blood vessels are dilated to increase the amount of oxygen carried in the blood, and the lungs work harder to meet the body's oxygen demands.
Blood volume increases during exercise, making the body more efficient, so it is not necessary for the lungs to work as hard.
The lungs determine the speed at which the heart pumps, so blood flows at a level that accommodates oxygen absorption in the muscles.
The lungs expand and contract, which increases the rate of blood flow so the muscles can
hope this helps</span>
I'm pretty sure it's difficulty concentrating
Unlike Static Stretching that is recommended for AFTER an exercise or athletic activity, Dynamic stretching can make a good warm-up before you are ready to preform. In dynamic stretching, you increase blood flow, increase the range of motion, and your joints get ready for movement. It focuses on different muscles.
Basically, doing dynamic stretching(which is moving your body while stretching), your body is prepared to move in actual athletic activity.