Venus Williams, LeBron James, Cristiano Ronaldo – elite athletes are extending their careers into their 40s. How?

Venus Williams is still playing professional tennis at 45. In August she became the oldest singles competitor to play in the US Open. Photograph: Elsa/Getty Images

At this year’s US Open, when 45-year-old tennis great Venus Williams stepped on to the court to play in doubles, it was alongside a teammate who wasn’t even born when Williams won gold in the singles at the Sydney Olympics.

Given that the peak performance age for a tennis player has traditionally been considered to be around the mid-20s, it was an extraordinary feat to be competing at a major, but Williams’ exceptional extension of her athletic career is increasingly common.