Sprint king Usain Bolt aims to crown his legacy with an unprecedented Olympic threepeat at the Rio Games, and to top that off by running the first ever sub-19 seconds 200 meters.

The long-striding Jamaican suggested he might not stop there, leaving open the chance he could extend his career beyond the 2017 season he has said would be his last.

Bolt has already swept the 100 and 200m sprints at the last two Olympics and added gold in the 4x100 relays in both Beijing (2008) and London (2012) with his Jamaican team mates.