FORMER champion thoroughbred Better Loosen Up has died at the age of 30 after battling a sudden heart problem.

Living Legends, a farm which stables retired racehorses, announced the eight-time group 1 winner had passed away overnight.

Better Loosen Up had a stellar career in which it earned a spot in Australia's Racing Hall of Fame in 2004. The son of Loosen Up had 45 career starts for 17 wins.

Perhaps one of the champion's most memorial wins was the 1990 Japan Cup in Tokyo, which solidified its champion status and inspired the quote from race caller Bryan Martin, “Better Loosen Up has won for Australia” – a quote that has stood the test of time.

Better Loosen Up also won the Cox Plate, Segenhoe Stakes, MacKinnon Stakes, Feehan Stakes, Blamey Stakes and the Turnbull Stakes in 1990, which sets it apart from other champions of the turf.

In the Cox Plate it came from an estimated 30 lengths off the lead to win in course-record time after the race commentator all but ruled it out during the run.

It subsequently won Australian Horse of the Year in 1991, which also became a defining year for the champion. It won the 1991 Australian Cup by defeating Vo Rogue by five-and-a-half lengths before a bowed tendon in its leg restricted its ability on the track.

Despite battling injuries, Better Loosen Up mustered the courage to run in the 1992 Cox Plate, where it arguably ran its career-best race. It finished third behind Super Impose, but won second place via protest over Let's Elope. It would retire from racing in February 1993 having won over $4.7 million in career earnings.

Better Loosen Up had four trainers throughout its career. Les Theodore trained it as a two-year-old before Bart Cummings took over for its three-year-old season. Colin Hayes took over at age four before his son and current trainer David Hayes trained it till it finished racing as a seven-year-old.