Breathing increases during exercise because of intensified energy demands placed upon the body. The cardiovascular, respiratory and muscular systems work together to keep up with these energy demands. When an individual is in shape, his lungs, heart and muscles efficiently turn oxygen into energy. This efficiency decreases the rise in heart rate, as well as breathing, during exercise.
Energy Creation
Whether the exercise is strength training or cardiovascular, the body needs energy to produce movement. The respiratory system inhales oxygen from the atmosphere. The oxygen then enters the lungs, diffuses into the bloodstream, and then travels to the heart. The heart then pumps the oxygenated blood to the body. During exercise, the heart sends most of the blood to the muscles where, inside the mitochondria of muscular cells, the oxygen combines with glucose (sugar) or fats to produce energy.
Increased Need for Energy
At rest, the body tries to conserve energy, using only as much energy as needed. When an individual begins to jog, row, swim, cycle or lift, sensory receptors in the muscles send messages to the brain, asking for more oxygen to create the necessary energy. The muscles ask for oxygen, so the heart must pump faster to get the oxygen to the muscles and the lungs have to take in oxygen at a rate that equals the heart's effort. Increased energy demand equates to an increased heart rate and oxygen intake. The end result is increased breathing during exercise.
Cardio vs. Strength Training
Breathing and heart rate increase faster during cardiovascular exercise than strength training. This is because cardio (aerobic) activities utilize energy from the entire body. Nearly all the muscles in the body must activate to propel the body forward during running and swimming, while strength training may only use the biceps muscles. Therefore, breathing increases at a faster rate while engaging in cardiovascular exercise.
Being in Shape
An individual who is "out of shape" gets out of breath easier for many reasons, one of them being that he has a hard time converting oxygen into energy. His lung capacity may be poor, his heart not strong enough to pump the amount of blood needed to cover energy demands of exercise and the muscles will not efficiently convert oxygen into energy. By contrast, an "in shape" individual has a high lung capacity, a strong heart with clear blood vessels, and the muscles are efficient at converting oxygen into energy.
