[4] He set a new national record in the decathlon in finishing sixth at the 2019 Pan American Games in Peru.
[6] He set a personal best decathlon points tally of 7,734 on June 27, 2021 at Thomas A Robinson National Stadium.
The following year, he finished in 17th place overall in the men’s decathlon at the 2022 World Athletics Championships in Eugene, Oregon with a total of 7,866 points.
In a heptathlon in Illinois at the end of January 2024, Mullings set PBs in six of the seven disciplines, winning with a national record of 6340.
He competed in Paris at the 2024 Summer Olympics in the decathlon, finishing in 13th place overall, with a new national record tally of 8226 points.