For Cristiano Ronaldo, it was a very on-brand family photograph.

Posing in a gym, the football icon flexed his muscular physique in trademark style, as his eldest son, Cristiano Junior, followed suit beside him.

The caption on X, where the Portuguese former Manchester United and Real Madrid forward posted the snap to his 115.5million followers, reads: ‘Tal pai tal filho’, or in English: ‘Like father, like son’. Indeed the teenager, who turns 15 this week and has already made a goal-scoring debut for Portugal Under-15s, seems to be following his father’s example of training hard.

But look carefully, beyond the familiar rippling abs and powerful leg muscles that have helped Ronaldo become a superstar, and you notice something else — the 40-year-old, who currently plays for Saudi Pro League club Al Nassr, has painted his toenails black.

So, is there a performance-related reason behind the five-time Ballon d’Or winner’s decision? Will this catch on?