P90x in the studio

Participants stretch in unison during P90X training class at Fitness 19 in Chino.

(Gina Ferazzi / Los Angeles Times)

July 9, 2015 5:52 PM PT

Instructor Ann Alperin leads her P90X training class at Fitness 19.

(Gina Ferazzi / Los Angeles Times)

Participants uses weights during P90X training class at Fitness 19 in Chino, Calif.

(Gina Ferazzi / Los Angeles Times)

Participants use varying weights during P90X training class at Fitness 19.

(Gina Ferazzi / Los Angeles Times)

Jovanie Villanueva of Ontario concentrates during P90X training class at Fitness 19.

(Gina Ferazzi / Los Angeles Times)

Jovanie Villanueva of Ontario pushes himself doing during P90X training class at Fitness 19.

(Gina Ferazzi / Los Angeles Times)

Instructor Ann Alperin demonstrates technique while leading P90X training class at Fitness 19.

(Gina Ferazzi / Los Angeles Times)