Racing is set to resume Friday at Santa Anita Park after 22 horses died this season.
The famed track near Los Angeles was closed to racing March 5.
On Thursday, the California Horse Racing Board limited the use of whips and approved changes to medication rules. Park owners and the Thoroughbred Owners of California had agreed earlier "to protect the safety and welfare of horses and riders in the state," said a statement from the Stronach Group, the park's owner.
Since late December, 22 horses have died at Santa Anita in Arcadia, California. Ten died during the same period last year.
The Los Angeles County district attorney's office assigned investigators to look into the horse deaths this month.
On Thursday, a group representing jockeys argued against whip restrictions, CNN affiliate KTLA reported. The representatives said whips were not connected to any of the deaths.
But two board members said they saw whips being overused on some of the horses that died.
"Going after a horse with a whip when it was obvious that the horse in question had nothing left to give is something I never want to see again," said Madeline Auerbach, the racing board's vice chair, KTLA reported.
The Stronach Group, which also owns Golden Gate Fields, said the agreement "enacts the most stringent medication policy in North America."
Santa Anita issued a statement on the deal Thursday.
"Horses will race with no race day medication with the exception of the diuretic Lasix, which will still be permitted, but at a maximum of 50% of the previous levels," the statement said. "Additionally, all horses born in or after 2018 will race at Santa Anita and Golden Gate will do so with no race day medication, including Lasix. This means all two-year-old horses starting in 2020 and after will be racing medication free."
The park dates back to 1907 and was featured in the 2003 movie "Seabiscuit."
Stronach Chief Operating Officer Tim Ritvo said, "The horses are the one thing that unifies us all. We are looking forward to welcoming everyone back to Santa Anita (Friday)."