Gym bosses say they are “extremely disappointed” at the government’s decision to allow pubs to reopen on 4 July but not indoor sports facilities.
Humphrey Cobbold, head of the Pure Gym chain, told the BBC indoor gyms were not high risk for coronavirus and his sites were ready to reopen safely.
And the boss of the David Lloyd group called the decision bizarre and illogical.
The government hopes gyms can reopen in mid-July, subject to health guidance.
On Tuesday, Prime Minister Boris Johnson promised to relax social distancing rules in the UK, allowing pubs, restaurants, hotels and and other firms to reopen after three months of lockdown.
But gyms and swimming pools are among businesses that will have to stay closed over fears they are not coronavirus safe.
Some medical experts say gyms could encourage the virus to spread, as they are humid and confined spaces with shared equipment. Heavy breathing during exercise could also transmit infections, they say.
But Mr Cobbold, who runs 269 gyms across the UK, said strict processes would protect customers and staff, with limits on the number of people per venue and members required to book their own spaces to exercise.
“Quite how the government can describe us as a close proximity venue relative to pubs of 600 sq feet, ours are 17,000 sq feet on average, [makes no sense],” he told Radio 5 Live’s Wake up to Money.
“We have excellent air extraction systems, much better than the systems in most offices and supermarkets, or cinemas and venues like that.”
He added that the firm had reopened its 230 European gyms over the last six weeks, with not a “single incident of transmission or infection”.
Glenn Earlam, boss of David Lloyd Clubs, called the government’s decision to prioritise reopening pubs over gyms “bizarre” and “completely illogical”.
“If people come to health and fitness facilities it helps boost their immune system. The chief medical officer has regularly said that health and fitness is one of the best things you can do to protect yourself from Covid-19,” he said.
There are fears that the effects of the pandemic could result in permanent closures of gym and leisure facilities. Nearly half of the UK’s public leisure facilities – more than 2,500 sites – may have to shut due to financial challenges, a survey by charity Community Leisure suggested this week.
The head of Greenwich Leisure, Mark Sesnan, told the BBC that his firm, which runs gyms, swimming pools and leisure centres for councils across the UK, was in a risky position.
“There is no money coming in and the expenses are still going out… At the moment it is still rescueable, but much longer and the country will have a problem with public facilities struggling with ever being able to reopen.”
A spokeswoman for the Department for Culture, Media and Sport said: “We are continuing to work with representatives from the gym and leisure centre sectors on plans for a safe, phased reopening with the ambition for this to happen from mid-July, subject to public health guidance.
“We need to make sure that plans are comprehensive with all risks minimised. We are fully committed to making sure the public can exercise and stay healthy, as outlined in our guidance for outdoor exercise.”