Technically, there are no factors that affect the speed of semen, since semen is the liquid in which sperm are found. It is made up of fructose and other substances, and provides a protective barrier for sperm so they can survive in the acidic environment of the vagina. However, sperm speed can be affected by unhealthy lifestyle choices or genetic factors. Many people use the terms "semen" and "sperm" interchangeably, even though they are actually two separate entities.
When asking about semen velocity, most men want to know if there is anything they could be doing to affect their sperm motility. There are several behaviors that men can engage in that can negatively affect the speed and overall health of their sperm cells. Tobacco smoking, for example, may be associated with abnormal sperm with low motility. Deficiencies in certain vitamins can also affect the speed of sperm.
Certain substances have been tested to determine if they affect "semen speed." Caffeine, for example, has been tested and found to increase male sperm speed for a temporary period. The exact amount needed may be different for each man. It is not recommended that men drink an unusual amount of caffeine in an effort to improve fertility, as this can have negative health effects.
If a patient asks a doctor to check their semen velocity, they are usually referring to sperm motility. In addition to maintaining a healthy lifestyle by avoiding drugs and maintaining a healthy weight, there are other factors that can come into play when it comes to male fertility. Certain genetic defects or hormonal conditions can also affect sperm speed and health, and are usually checked during an exam.
The test used to assess sperm motility usually involves a man ejaculating into a sterile cup. This is achieved through masturbation that is done in a fertility clinic. Once the semen has been collected, it is examined under a microscope. Sperm are visible, and a doctor can see if there are deformed, slow-moving, or dead sperm.
Many defects can be corrected by surgery or hormone replacement therapy. Sperm samples may be taken at intervals to assess general health. Sperm speed isn't as important as overall health, but since they can only live for a few days once they enter the female body, it's important that they move well enough to reach and fertilize an egg.