Does Exercise Increase Your Number of Capillaries?

Regular exercise is associated with a host of health benefits. Among these benefits, regular exercise has positive effects on blood flow and blood vessels. Capillaries, the smallest blood vessels in the human body, are responsible for transporting nutrients and wastes to and from your body's tissues. As these tiny vessels play an important role in your overall health, knowing how exercise affects capillaries is important.

Capillaries respond to your body's needs, supplying blood and oxygen and removing wastes as these actions are needed. Due to the demands placed on different parts of your body during exercise, the ability of your capillaries to respond to your body's needs plays an important role in fatigue and endurance. Capillary density refers to the amount of capillaries present at a certain site in your body.

While exercise temporarily increases the capillary density at muscle sites, it is possible to improve these changes in capillary density with training. A 2009 study conducted by researchers at Duke University provides evidence for this, with both men and women developing increases in capillary density after a six-month exercise program.

Increased capillary density allows for greater oxygen transport to your muscles, improving their ability to perform intense exercise. In addition to improving muscle function by increasing capillary density, exercise improves capillary function regardless of capillary density. Researchers at the Peninsula Medical School in Exeter, U.K., found support for this in a 2009 study. In addition to reporting that capillary function improves with exercise, they explored the decline in capillary function with age, finding that exercise helps prevent this decline.

While exercise can lead to increases in capillary density and improved capillary function, there is some evidence showing that exercise training can lead to the development of new capillaries. In a 2008 study conducted at the University of Missouri-Columbia, the improved function and increased density of capillaries with exercise training was explored. While such effects of exercise were supported by researchers' findings, they also found evidence for capillary growth, or the development of new capillaries with exercise training.

Following an exercise program for an extended period of time can lead to improved capillary function, increased capillary density at your muscle sites and the growth of new capillaries, where needed. While the development of new capillaries indicates that exercise does increase your number of capillaries, such increases are marginal and may not affect all people. Though exercise has the potential to increase your number of capillaries, the major effect of exercise on your capillaries involves improving those that you already have.