The main goal of your heart and lungs during exercise is to increase the flow of oxygenated blood. Your muscles need oxygen to produce the energy necessary to sustain activity. It is the job of the lungs to oxygenate blood and remove carbon dioxide, a byproduct of cellular metabolism. The heart must increase its work to deliver more blood, and more quickly, to the muscles and lungs.
Your heart responds to exercise by increasing the number of contractions, or beats, it performs each minute. Your heart rate can increase from 60 to 100 beats per minute at rest, all the way up to around 200 beats per minute, depending on your age, gender and fitness level. By increasing how many times it beats each minute, your heart is able to supply your body with a larger amount of blood during exercise.
Stroke volume is the amount of blood your heart pumps out with each beat. To fulfill the need for extra blood during exercise, your stroke volume also increases. In fact, your stroke volume can increase by 40 to 60 percent from its resting rate, strength and conditioning specialist Phil Davies writes for the Sports Fitness Advisor website. As more blood returns to your heart, the ventricles fill with a greater amount of blood. This allows for optimal stretch inside the cardiac muscles, resulting in a stronger beat and more blood ejected.
Your lungs increase their work during exercise. This is essential to increase the amount of gas, oxygen and carbon dioxide, during exercise. At rest, your lungs move about 6 L of air per minute; during maximal exercise, your lungs can move up to 192 L of air each minute. This can mean an increase from 12 breaths per minute at rest to 48 breaths per minute during exercise.
To increase air movement and frequency of breaths, your lungs are equipped with special inspiratory and expiratory muscles. During rest, your diaphragm and intercostal muscles open up the lungs to force air in. Exhalation is a passive function done without the use of muscle force. However, during exercise, accessory inspiratory muscles aid inspiration — and exhalation becomes a forceful action. During exercise, the sternocleidomastoid, scalene and trapezius muscles also work to open the lungs to bring in more air, more frequently. During exhalation, the intercostal and abdominal muscles work together to force air out, expelling carbon dioxide.