UPDATE: On July 13, the day Santa Clara County allowed fitness centers to reopen, the county Public Health Department released a statement in the afternoon that reversed its updated order because it was recently added to the state's monitoring list, effectively shutting down all gyms by Wednesday, July 15.

Starting Monday, gyms and fitness centers that have been shuttered for months throughout Santa Clara County will finally be allowed to reopen. But they're going to have to follow some pretty stringent rules that go far beyond what the state requires.

County health officials released guidelines this week outlining how gyms and fitness facilities will be allowed to reopen starting Monday, July 13, marking the end of four months of mandatory closures due to the coronavirus pandemic. Patrons will be required to wear face coverings at all times -- even while exercising -- and gyms must cap the number of customers based on the square footage of the facility.

Perhaps the most onerous restriction is the blanket ban on any indoor cardio and aerobic exercises, including the use of treadmills, exercise bikes, elliptical machines and any activity that "induces heavy breathing and elevated heart rate." Indoor dancing and calisthenics are also prohibited, as are indoor and outdoor contact sports.

In drafting the rules, health officials say gyms and fitness centers are important to reopen, but also pose significant public health risks, with communal equipment and heavy respiration mostly taking place indoors, where the risk of transmission is higher.

"Gyms and fitness facilities must take extra precautions to reduce the risk of COVID-19 transmission for clients and staff," according to the guidelines. "Gym and fitness activities are strongly urged to move activities and equipment outdoors wherever possible."

Other counties that were quicker to reopen gyms, including San Mateo County, have largely deferred to state guidelines for their own safety precautions. Those rules still require plenty of precautions, including frequent and thorough cleaning of locker rooms and showers and requiring staff or patrons to wipe down equipment and mats before and after each use, but are noticeably more lax.

In Santa Clara County, all locker rooms, showers, indoor pools, spas and saunas must remain closed.

YMCA fitness centers will be reopening later this month in a phased approach, with some branches opening on July 20, followed by another batch opening July 27. Joey Sanchez, the communications director for YMCA of Silicon Valley, said the nonprofit is taking the extra time to look through the county's requirements for a smooth opening.

"We're not planning to jump in as quickly as possible just because it's available," he said. "We're making sure that everything they are requiring is adhered to, that everything is properly sanitized and all our personnel are properly trained."

Sanchez said the YMCA has an edge in the sense that it already has experience reopening gyms in San Mateo County earlier this month, albeit under a very different set of rules. He said the operations team was surprised to see Santa Clara County will be requiring face masks at all times, even when customers get to their station and begin working out.

The indoor prohibition on cardio workouts will also be tough to navigate, and may require them to push some of those activities outdoors, he said.

"The surprise for us was not being allowed to do indoor cardio. That's a huge thing for people coming to the Y obviously, and so we'll have to find different ways for people to work out."

Another sticking point is the cap on the number of people allowed inside at any given time, limited to one staff member per 250 square feet inside the facility and one customer for every 150 square feet. YMCA centers in Santa Clara County will likely have to use a reservation system to keep track of capacities, Sanchez said. Anyone interested to see when individual YMCA locations will open can check the nonprofit's [www.ymcasv.org/reopening-guide reopening webpage.

24 Hour Fitness, which operates more than a dozen gyms in Santa Clara County including two in Mountain View, is expected to reopen all of its local facilities right on July 13, with some big changes in mind. Open hours are being cut down, and gyms will have 30 minute closures during the day for club cleaning in between 60-minute workout sessions. Members are asked to make reservations one day in advance of showing up, and in other counties have been required to wear masks "unless extreme physical exertion or health restrictions" would prevent it.

In order to adhere to social distancing, the fitness center chain has decommissioned cardio and strength equipment previously packed tightly together to ensure proper spacing.

Planet Fitness, a national chain that operates three gyms in Santa Clara County, declined to give a start date for its reopening plans. Becky Zirlen, a spokeswoman for the club, said that safety is a top priority, and that the reopening date will be determined with that in mind.

"Now more than ever it's important to stay active, in order to stay healthy, and we look forward to safely and responsibly welcoming our members back," she said.

On top of social distancing and other health requirements, the chain will have to curtail its tradition of serving up pizza and bagels to its members, with county rules prohibiting indoor dining at fitness centers. Similar to restaurants, gyms can still serve up takeout meals or allow patrons to eat outside.

Gyms will be reopening as part of a larger update to the county's health restrictions aimed at curbing the spread of the coronavirus, which will also allow hair salons, nail salons and activities that can safely accommodate small gatherings. The order, announced on July 2, was briefly thrown in limbo over the Fourth of July weekend when state officials initially denied the county's plans. After a confusing back-and-forth, state officials finally gave Santa Clara County the go-ahead to proceed with its reopening plans on Monday.

The coronavirus and mandatory shutdown of fitness centers across the country has had a disastrous financial impact on gyms, which are among the last businesses that have been allowed to reopen. 24 Hour Fitness, based in San Ramon, announced last month that it was filing for Chapter 11 bankruptcy protection and will shutter 100 locations throughout the U.S., including 13 Bay Area locations spanning from Morgan Hill to Fairfield. The two gyms in Mountain View will remain open.