The Gym Group (GYM.L), which operates 190 budget gyms across the UK, saw its revenue hit hard by the pandemic but has seen demand grow more recently and is hopeful of better results going forward.
In the six months to June 2021, during which gyms were only open for two months, its revenue was down 21.4% year on year to £29.3m ($40.4m).
In the periods of government-enforced closure, the gyms earned close to zero revenue as they "froze" memberships.
Pre-tax loss was £28.5m, roughly the same as last year.
But The Gym Group's stock was up 7% on Thursday afternoon after it said a strong recovery in membership numbers followed the re-opening of gyms in April, with 730,000 members at 30 June 2021, up from 547,000 at the end of February.
Over two-thirds of its members are under the age of 34, and the company said younger people often lacked space to work out at home.
"The physical gym will always be really important for people and I think that's coming through in our numbers," CEO Richard Darwin told the BBC's Today programme.
“The results reflect both the significant disruption caused by the pandemic and the start of our recovery out of COVID,” the company said.
“With gyms re-opening in April and all remaining COVID restrictions being lifted in July in England, we have seen strong demand for our gym memberships and now look forward to a period of sustained recovery and accelerated growth.”
The firm opened three new sites in July and August and plans to open 37 more by December next year by converting former shops.
"We have identified some exciting growth opportunities to expand our estate further and raised additional funds from shareholders to capitalise upon them," said Darwin.
The company said it took a number of actions to mitigate the impact of the pandemic, including reducing costs and capital expenditure to conserve cash.
It also received government support in the form of business rates relief, furlough payments and local authority grants.
Gyms reopened in England on 12 April this year, and later in Scotland, Wales and Northern Ireland.
Watch: How to live off a student loan