Sperm motility is an important sperm characteristic necessary for fertilization of the egg, as they move through the female reproductive tract to reach the egg. Low sperm motility is a cause of male infertility. There are two types of sperm motility, referring to the way individual sperm swim. Progressive motility refers to sperm that swim in a mostly straight line or large circles. Nonprogressive motility refers to sperm that do not move in a straight line or that swim in very tight circles. In order for sperm to pass through the cervical mucus and fertilize the egg, they must have a progressive motility of at least 25 micrometers per second. Poor sperm motility, or asthenozoospermia, is diagnosed when less than 32 percent of sperm move efficiently. Sperm motility factors Worldwide, about 60 to 80 million couples are affected by infertility, with rates varying from country to country. Infertility in men results from sperm disorders, the most common of which are: Low sperm count or oligospermia; Poor sperm motility; Abnormal sperm shape or teratospermia. About 90% of male infertility cases are caused by low sperm count, but poor sperm motility is also an important factor in the condition. Causes of Low Sperm Motility The causes of low sperm motility are varied and in many cases unexplained. Damage to the testicles, which produce and store sperm, can affect the quality of semen. Common causes of testicular damage include: Infection; Testicular cancer; Testicular surgery; Congenital defect; Undescended testes (cryptorchidism); Trauma. Long-term use of anabolic steroids can reduce sperm count and motility. Illicit substances, as well as some herbal medicines, can also affect sperm quality. Varicocele, a dilation of the venous vessels in the scrotum, is also associated with low sperm motility. Among other factors, recent evidence suggests that oxidative stress plays a major role in the etiology (cause) of defective sperm function. Sperm spontaneously produce a variety of reactive oxygen species (ROS), including superoxide anion, hydrogen peroxide, and nitric oxide. Produced in small amounts, reactive oxygen species are functionally important in driving the tyrosine phosphorylation cascades associated with the capacity of sperm to fertilize an egg. However, when the production of reactive oxygen species exceeds the limited antioxidant defenses of spermatozoa, a state of oxidative stress is induced.This condition is characterized by peroxidative damage to the sperm plasma membrane and DNA strand breaks in the nucleus of the cells. Oxidative stress not only impairs the fertilizing potential of sperm, but also the ability of these cells to create a normal, healthy embryo. As a result, DNA damage in sperm is associated with an increased incidence of spontaneous abortions and various types of morbidity in the offspring. These findings in the pathophysiology of defective sperm function have clear implications for the diagnosis and treatment of male infertility, particularly with regard to the potential importance of antioxidant therapy. These concepts may also be relevant to the design of new approaches to male contraception. References: 1. ScienceDirect. Barak, S., & Baker, H. W. G. (2016). Chapter 141 — Clinical management of male infertility 2. Kumar, N., & Singh, AK (2015, November 25). Trends of male factor infertility, an important cause of infertility: A review of literature. Journal of Human Reproductive Sciences 3. PubMed. New insights into sperm physiology and pathology