Gyms in South Korea's capital Seoul and its surrounding region have been told not to play music with a tempo higher than 120 beats per minute (bpm), in order to limit the spread of Covid-19.
Treadmills will be limited to a maximum of 6km/h (3.7 mph).
Health officials say the restrictions will prevent people from breathing too fast or splashing sweat on each other.

A quick look at K-pop bpms suggests Blackpink fans might suffer a bit more than followers of BTS.
South Korea is battling a new outbreak of the virus, with 1,100 new cases recorded on Sunday.
Prime Minister Kim Boo-kyum warned on Friday that the country had reached "maximum crisis level".
Those attending exercise classes such as Zumba, spin and aerobics in the greater Seoul area will face the 120bpm limit from Monday.
People are also only allowed to spend two hours at a time at indoor sports facilities and must not use the shower.
All sports facilities must close by 22:00.
The move has been questioned by gym owners.
Kang Hyun-ku, who owns a gym in Seoul, asked whether there was any proof a choice between classical music and BTS had an impact on spreading the virus.
He also told Reuters many people used their own earphones, asking: "How do you control their playlists?"
But officials say the measures help prevent gyms from closing completely.

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Experts say it is hard to know whether people have been infected at gyms. Figures from the UK last year suggested that they were not a significant hotspot for infections.