Sperm swim up to 70 per cent faster when they have a lazy tail

By Jason Arunn Murugesu

Sperm with an inactive portion of their tail actually swim faster

Sebastian Kaulitzki / Alamy

A human sperm can move up to 70 per cent faster if it has a lazy tail, a finding that could pave the way for new fertility diagnostic tests.

Sperm cells use their tails to swim, though some don’t use the whole tail – leaving a piece at the end inactive. This part only constitutes about 3 to 5 per cent of a normal sperm tail – which is usually between 50 and 55 micrometres long – and doesn’t actively bend like the rest of …