The process that starts sperm swimming as they get near a woman’s egg has been found. This discovery could possibly lead to finding a way to improve sperm mobility for men with sperm that don’t swim as well as they need to. One day, it could even help with new forms of male contraceptives, reports the BBC.

So aren’t sperm always swimming fast? Well, no. They’re not on the move right from the get go. They delay their mad dash until they’re closer to the egg because they have limited resources and need to make their sprint count!

Scientists already knew that sperm’s activity levels were determined by their own pH (that’s how acid or alkaline they are on the inside). What they didn’t know was how sperm could alter their internal pH at the right moment to make themselves race onwards. But now researchers at the University of California, San Francisco, have uncovered the secret.

Basically, sperm have tiny pores on their surface that allow them to change their pH. It’s this change that makes their tails move. It seems that their pores open and respond to a substance in a woman’s reproductive tract. The levels of this substance are greater near the egg. So, the closer they get to that egg, the quicker they swim. Genius!