GAINESVILLE, Fla. (AP) _ Arthur A. Jones, whose invention of Nautilus exercise equipment revolutionized the fitness industry, on Friday announced the gift of nearly $8.5 million to the University of Florida.

The donation will be shared by the school's Health Science Center and Center for Exercise Science, Jones said.

The center is operated by the colleges of Medicine and Health and Human Performance. The center is testing Jones' latest invention, a computerized machine designed to evaluate and rehabilitate the lower back.

Jones' donation of $8.47 million was announced at a morning news conference at his 500-acre ranch near Ocala.

''I have a longstanding interest in physical training and wellness, and my support of the University of Florida will boost the research of lower back pain, one of man's most nagging problems,'' Jones said.

''As the beneficiary of the largest gift in the history of the University of Florida and our state university system, we welcome the opportunity to join in his crusade against lower back problems,'' University President Marshall Criser said.

Officials said the health center's share of Jones' donation will help pay for a $39 million research building under construction.

In the past six years, Jones has donated more than $1 million for medical research and continuing medical education programs, and two years ago he funded the early clinical trials of his new lumbar machine at the university with a $350,000 grant and equipment donated by his MedX Corp.

He sold his Nautilus empire in 1986 to devote his time and energy to MedX, which began marketing the Lumbar Extension Machine later that year.