Stroke volume increases during exercise because the body's demand for more oxygen-filled blood increases, and an increase in stroke volume, due to contractions that are more powerful, will help eject more blood that can be distributed throughout the entire body, as reported by HSC Online. Stroke volume is better defined as the amount of blood that is pumped out of the heart by the left ventricle during each contraction, and is measured in milliliters per beat. By determining the stroke volume, medical professionals are able to determine the amount of blood that is being pumped, and the amount of oxygen that is delivered to the muscles.
Stroke volume only increases at exercise intensifies to between 40 and 60 percent, at which point it is said to plateau, as it has reached it maximum limit and capacity, even up until the body has reached exhaustion.
The body position that an individual is in when exercising will also affect stroke volume. Research has found that an upright body position will increase stroke volume more than a supine body position, because the resting stroke volume values are higher in the supine body position since the blood can easily flow back to the heart. Stroke volume needs to compensate for the effects of gravity.