Pollution from the burning of Indonesia's rain forests appears to be claiming another casualty: physical fitness in Singapore.
Poor air quality is keeping people indoors, denting demand for outdoor exercise in the usually balmy city-state.
"We're an outdoor fitness company, with up to eight sessions a day outside," Lisa Clayton, a director of OzFit/UFit Bootcamps, said Wednesday. "We have had to cancel pretty much most of them over the last two weeks."
She said her company usually catered to as many as 100 people a day training outside, but has instead hosted bootcamps at indoor locations, such as condominium function rooms, for about 60 people a day.
What's colloquially called the haze, but is actually air pollution, is an annual event in Singapore as Indonesians deliberately set forest fires to clear land, but this year, it's lasted longer than usual because El Nino weather conditions mean there's less rain.
The Pollutant Standards Index, a global gauge of air quality, ranged between 97 and 111 in Singapore early on Monday, after several days of less-gritty levels under 100, according to the National Environment Agency (NEA).
A level between 100 and 200 indicates unhealthy air quality, while levels above 300 are considered hazardous. The gauge climbed over 300 in late September but hasn't yet topped the 400-plus mark hit in 2013.
Indonesia finally accepted Singapore's offer of personnel and equipment to help fight the forest fires on Wednesday after weeks of waffling over the decision.
Homebound residents aren't just bad for Singapore's fitness companies. The local economy is already hurting, with some analysts believing it slipped into a recession in the third quarter, and the haze is likely to take a further bite out of consumption.
"The protracted period of hazy conditions will certainly weigh on the retail industry, who will likely see their slim margins (on already high operating costs) being eroded further with households opting to stay home and tourists deferring their plans to visit the region," Weiwen Ng, an economist at ANZ, said in an email last week.
He noted that previous years' hazy seasons had resulted in sharp drops in retail sales, even though the city-state's malls tend to be packed on days when the air quality worsens. Many Singaporeans don't have air-conditioners in their homes.
"While they might seek safety in the air-conditioned malls, I doubt they will spend," Ng said.
Consumers certainly aren't spending at outdoor-focused businesses.
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"I have lost 90 percent of my business," said Isabella Malique, the owner of the SUP School, which rents standup paddleboards at the beach on Sentosa island, a resort just off the coast of Singapore.
"I don't even have enquiries," she said, adding that she was concerned it would take a long time to regain lost interest once the haze finally clears.
She has another worry: the end of the haze is likely to be followed closely by the start of Singapore's rainy season, which may leave her business with little income for nearly six months.
Those customers aren't necessarily searching out gyms to keep up their fitness level.
Pure Group, which operates both gyms and yoga studios, said that member check-ins hadn't changed much over the past month or so.
"As much as we would like to think that many members are avoiding the outdoors and increasing their visits to the gym, this is not entirely the case," Hannah Yang, the marketing manager at Pure, said via email last week. "Many have taken ill due to the haze and have been putting yoga and gym aside for the time being."
Effects of the haze can range from respiratory symptoms, such as coughing and asthma attacks, to fatigue and headaches.
Sports teams are also struggling to practice.
"We've not been able to fully relocate training indoors," Thomas Gascou, the captain of the German Dragons, a dragon boat team, said Thursday. Dragon boating is an Asian paddling sport, with teams of 10 or 20 paddlers competing in long boats.
The haze has forced the German Dragons to cancel most of its water-training sessions over the past few weeks, Gascou said, noting that one session held when the air quality was "borderline" resulted in several people feeling light-headed and sick.
He moved some of the general fitness training to one of the government's community gyms but noted that while outdoor "land" sessions generally see as many as 60 people, that dropped to around 20 indoors.
All the effort to continue training may be for naught: There's a strong chance that the haze will force the next race, the Singapore River Regatta, scheduled for October 31, to be canceled or postponed.
It wouldn't be the first competition to get the axe; the first day of the international FINA Swimming World Cup on October 3 and the Race Against Cancer, a 15km and 10km running race set for last month, were both cancelled.
—By CNBC.Com's Leslie Shaffer; Follow her on Twitter