A detailed study of the effect of videoframe rates of 25, 30 and 60 Hertz on human sperm movement characteristics

A comparison was made of the movement characteristics of human spermatozoa analysed at three videoframe rates (25, 30 and 60 Hz) using two computerized motility analysers from Hamilton-Thorn Research (the HTM-2030 and the IVOS) operating at 25 and 30 Hz respectively. Analysis at 30 and 60 Hz was performed on the IVOS. The use of uncapacitated, capacitated and pentoxifylline-stimulated spermatozoa ensured a full range of movement characteristics was analysed. The velocity parameters curvilinear velocity and average path velocity were highly frame-rate dependent, and mean values increased with videoframe rate. An interaction of framing rate and time of data collection resulted in an increase in straight-line velocity with framing rate. Mean lateral head displacement and linearity were similar at 25 or 30 Hz but significantly depressed at 60 Hz. Beat-cross frequency increased by 74% when analysed at 60 rather than 30 Hz. The following criteria: curvilinear velocity > 100 microns/s, linearity < 65% and lateral head displacement > 7.5 microns, were used to define hyperactivated spermatozoa. Significantly more hyperactivated cells were identified at 30 Hz than 25 Hz (1-10%) but not at 60 Hz. A different population of cells is likely to have been identified as hyperactivated at 60 Hz due to alterations in component movement parameters from which the definition of hyperactivation was derived. In conclusion, direct comparisons should not be drawn between data analysed at 25 and 30 Hz. Analysis at 60 Hz introduced complex alterations which made simple comparisons with 30 Hz data invalid.