Human sperm move poorly in zero gravity

Research by Spanish scientists shows that in a zero gravity environment, human sperm lose vitality and mobility.

Scientists published their findings in the journal Acta Astronautica in October, aiming to explain the future of human fertility in space. To investigate the impact on human sperm, the team decided to expose it to zero gravity using parabolic flight .

Parabolic flight simulates microgravity. (Photo: Karlos Garciapons/Shutterstock).

Fifteen volunteers were selected with suitable sperm, and the analysis was performed before the flight. The sperm samples were divided into two groups, one experiencing the zero-gravity environment and the other on the ground as a control. After the flight, the sperm samples were returned to the lab for analysis.

The team found that exposure to short-term gravity changes, including microgravity, when sustained during parabolic flight significantly reduced motility and vitality in fresh sperm samples. They suggest this could be of great importance for any long-term human spaceflight missions.

According to scientists, in the future, if humans are in space for long periods of time with exposure to different peaks of microgravity and hypergravity, which can last from several months to several years, then reproduction may be a problem that needs to be solved.

However, the team did not pinpoint the mechanism that reduced sperm motility, and the experiments only involved a few seconds of weightlessness. "What the effects of longer exposure might be also need to be clarified ," the team said.