Effect of image sampling frequency on established and smoothing-independent kinematic values of capacitating human spermatozoa

It is known that image sampling frequency affects sperm kinematic values, although no study has considered the relative effect upon hyperactivated and non-hyperactivated spermatozoa. We determined the relative effect of image sampling frequency on the classification of capacitating human spermatozoa, using the established kinematic measures as well as a series of new, smoothing-independent kinematic measures. Spermatozoa were prepared by direct swim-up from semen and sperm movement was recorded using a video system which gave 201 images/s on freeze-frame playback. Trajectories were reconstructed manually and kinematics were determined using the (x, y) co-ordinates of each track point. Lower image sampling frequencies were approximated by considering every second, third, fourth, sixth and eighth track point for each trajectory. Of the 22 kinematic values investigated, only three were not significantly affected by sampling frequency in both hyperactivated and non-hyperactivated spermatozoa. Also, significant differences were observed between hyperactivated and non-hyperactivated tracks at all image sampling frequencies studied for all but four kinematic measures.