Measurement of sperm motility of samples collected from eight different research centers. (A) Sperm motility (%). (B) Progressive sperm motility (%). (C) Rapid sperm motility (%). (D) Medium sperm motility (%). (E) Slow sperm motility (%). (F) Curvilinear velocity (VCL, μm/s). (G) Straight line velocity (VSL, μm/s). (H) Average path velocity (VAP, μm/s). (I) Beat cross frequency (BCF, Hz). (J) Amplitude of lateral head displacement (ALH, μm). Sperm motility and motion kinematics are presented as the mean ± SE. Superscripts a, b, c, d and e indicate significant differences between sperm parameters by one-way ANOVA of variance (p < 0.05, n = 9).