The 400m individual medley is one of the toughest events in swimming.

The event takes about four and a half minutes for the fastest women and a little over four minutes for the speediest men. Athletes need to master all four of swimming’s strokes — and the tricky transitions required to move between them.

It’s a fascinating event to watch as competitors have different strengths, which can result in frequent lead changes (unless, of course, you’re watching Summer McIntosh who can lead the race from the buzzer).