A few years ago, health and fitness advocate Gabrielle Reece started training friends on Kauai whose busy lives left little time for workouts. She took them to an old warehouse and fired them up with a circuit of high-intensity exercises.

It became so popular — Reece says interest in it exploded — that she was able to create a deal with 24 Hour Fitness to bring her workout philosophy and exercise routines to its gyms.

The 45-year-old Reece, a former professional volleyball player and the wife of big-wave surfer Laird Hamilton, worked with the fitness chain to create a 50-minute routine that uses high-intensity exercises. Both Reece and 24 Hour Fitness claim the routine — dubbed HIGHX Training — will burn fat and build lean muscle.

HIGHX Training will be offered in group sessions. Although it isn’t expected to be in 24 Hour Fitness gyms here until June, Reece led a demonstration class Saturday at the chain’s Pearl City location.