UKactive, a not-for-profit body for fitness chain, has written to Mr Johnson urging him to take account of plans drawn up the industry operate safely, ensuring social distancing, long gaps between classes and strong infection control.
The letter, written by chairman Baroness Tanni Grey-Thompson, urges ministers to consider the need to boost the fitness of the country in order to combat the coronavirus threat.
Describing exercise as a “wonder drug” and “a key part of the answer”, the former paralympian said the evidence showing the role that fitness plays in physical and mental wellbeing is “absolutely irrefutable”.
She wrote: “It is well known and supported by research that general good health – of which physical activity and fitness is a key part – is essential for a healthy immune system that can help people fight viruses such as Covid-19.”
Acknowledging the “difficult balancing act” facing the Government, the letter said: “Getting active in a controlled environment is a key part of any programme to reduce weight and obesity, which is now known to be a contributory factor to the severity of Covid-19 cases.”
Undue delays to gym reopenings would deny many people the chance “to safely improve their health, strengthen their immune systems and ensure they are in the best shape they can be for whatever the future brings”, she said.
The letter warned that, without reopenings soon, the industry fears the permanent closure of more than 2,800 facilities and the loss of over 100,000 jobs.
Glenn Earlam, the chief executive of David Lloyd Leisure, said outdoor swimming pools and leisure centres are capable of reopening “quite easily” within weeks under social distancing measures
Arguing that gyms should be allowed to open before shopping centres, Mr Earlam said he believed there was a “prejudice against certain sectors”.
He added: “The evidence suggests that keeping the body fit and healthy could be one of the best things to do to prevent Covid-19 – but I think gyms and leisure centres are quite far down on the pecking order of opening things up again, which seems pretty counter-intuitive.”
Six in 10 adults in the UK are overweight or obese, and the average Briton normally walks for less than 10 minutes a day, research suggests.