Endurance exercise, such as jogging, swimming and cycling, increases your blood volume over time. Blood-volume adaptations begin after a single bout of exercise and amplify within weeks of training. Enhanced blood volume enhances your exercise performance and cardiovascular fitness.
Blood Volume Defined
Blood volume is composed of red blood cells and blood plasma circulating throughout your body. While red blood cells transport oxygen, blood plasma is a yellowish liquid that carries your red blood cells. Composed mostly of water, blood plasma contains dissolved proteins, hormones and minerals. A typical adult male maintains a blood volume of 5 to 6 L, while females typically have 4 to 5 L of blood. Increased blood volume provides greater amounts of blood to your heart and increases how much blood your heart pumps per beat and per minute.
Blood Plasma and Hormonal Changes
Three factors influence increased blood volume from exercise. For example, cardiovascular exercise boosts the release of anti-diuretic hormone and aldosterone -- two hormones that cause your kidneys to retain or reabsorb water. Increased water retention within your kidneys increases blood plasma levels and produces a greater blood volume overall. Generally, plasma volume increases within two to three weeks of endurance training.
Blood Plasma and Changes in Blood Protein
Exercise raises the amount of proteins within your blood plasma. According to the book "Exercise Physiology: Human Bioenergetics and Its Applications" by George A. Brooks, Thomas D. Fahey and Kenneth M. Baldwin, levels of a common blood protein known as albumin increase within your blood plasma within one hour of your first bout of exercise. Greater levels of plasma protein cause water retention within your blood plasma, which results in elevated blood volume.
Red Blood Cell Changes
For some individuals, exercise increases the total number of red blood cells within the body. A typical athlete has a greater amount of red blood cells than an individual who does not exercise regularly. Additional red blood cells enhance the transportation of oxygen to working muscles during exercise and increase your blood volume.
Detraining and Blood Volume
Detraining is a loss of fitness from quitting exercise. Like most exercise-induced health benefits, your blood volume reverts to a pre-training level if you stop exercising. You may experience reduced exercise performance after a few weeks without working out. However, you regain an increased blood volume within a few weeks of restarting your workout routine. Consult a doctor before beginning an exercise program.