Factors affecting sperm motility. I. In vitro change in motility with time after ejaculation

Semen specimens from 33 donors were analyzed intermittently between 1 and 24 hr after ejaculation. Motility was determined objectively by analyzing still-camera photomicrographs taken with the aid of the new multiple exposure photography (MEP) technique, from which the following information was obtained: the percentage of motile spermatozoa, the average velocity and frequency distribution of spermatozoal velocities, and index of motility as well as sperm concentration. From curves drawn for each of the 33 analyzed specimens, these conclusions were drawn. The percentage of motile spermatozoa decreases progressively, beginning 1 hr after ejaculation, at a rate of about 5% to 10%/hr. In the majority of cases, sperm velocity increases for the first 4 hr and then decreases gradually. There is no unique pattern of sperm motility and velocity with time for all specimens, especially during the first 4 hr. However, three typical curves of motility change were found during the first 4 hr: increase in motility, moderate decline in motility, and rapid loss of motility. The frequency distribution of velocities of motile spermatozoa revealed typical normal curves at all times, but these curves became flatter as time elapsed. An explanation for these divergent patterns and the possible role of these findings in some physiologic and clinical problems are discussed.