Human sperm motility in a microgravity environment.

We carried out clinostat and parabolic flight experiments to examine the effects of a microgravity (µG) environment on human sperm motility. Semen samples were obtained manually from 18 healthy men (aged 27.4 ± 5.4 years) who had given their informed consent. In clinostat experiments, samples that were left stationary were used as a stationary control. Samples rotated vertically and horizontally were used as a rotation control and a clinostat rotation, respectively. In parabolic flight experiments using a jet plane, sperm motility was compared for each parameter at µG, 1G and 2G. The state of 1G during the flight was used as a control. Sperm motility was determined using an automatic motility analyzer HT-M2030 in a microgravity environment. All parameters of sperm motility tended to be lower in clinostat rotation compared with rotation control at both low-speed and high-speed, but the differences were not statistically significant. In parabolic flight, sperm motility and parameters of linear movement were decreased ( < 0.05). There was no significant difference between µG and 2G, but sperm motility was significantly decreased at µG than at 1G. Our findings suggest that sperm motility is reduced under µG. (Reprod Med Biol 2005; : 161-168).