"We are not staying open for financial gain but more for our members' mental and physical well-being," says Chris Ellerby-Hemmings, the co-owner of EmpoweredFit gym in the Wirral.
"The reason for doing it is to be listened to."
The gym, which has 14,000 members, is one of dozens in Merseyside that have remained open despite new lockdown rules ordering them to shut.
Some medical experts say gyms could encourage the virus to spread, as they are humid and confined spaces with shared equipment.
But Mr Ellerby-Hemmings told the BBC his gym was Covid secure. "I want to ask the government or local government to show us the evidence as to why we should be closed."
The Liverpool City Region is the only area to be under the toughest Tier Three Covid-19 restrictions which came into effect at midnight, making it illegal for gyms in the area to open.
Any venue mandated to close that remains open faces fines of up to £10,000 for repeated offences, Liverpool City Council said.
Mr Ellerby-Hemmings is acting as spokesperson for the outlets defying the order to close. He says "gyms are not a major spreader of Covid" and there have not been any cases of Covid in the gyms that have remained open, either before or after the previous lockdown.
He also points to research by the gyms' trade body UK Active which found that for 22 million visits across England between 25 July and 13 September only 78 cases have been reported.
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