Exercise classes set to high-tempo music were banned in South Korea on Monday under the country’s strictest and most unusual Covid restrictions to date.

As part of measures to try to stem the virus, treadmills must be set at a maximum of 6 kilometres per hour (3.7 mph), the Yonhap news agency reported, without explaining why.

In another new rule, group dance programmes, such as spinning, aerobics, hot yoga, gymnastics and skipping, must be carried out with low-tempo music between 100-120 beats per minutes, it added.

Last year, after dozens of people were infected with Covid at fitness dance classes at several sports facilities within less than a month, Korean researchers said that transmission could have been exacerbated by the intensity of the workouts.

The restrictions are in place for at least two weeks in the capital, Seoul, and neighbouring areas, which are at the centre of South Korea’s rapidly spreading fourth wave. On Friday, the country reported its highest ever one-day number of new Covid infections at 1,378.

Coronavirus South Korea Spotlight Chart – Cases default

This time around, there have been fewer serious cases and deaths than in previous outbreaks with many older and otherwise vulnerable people having received vaccines. But health authorities are worried about the spread of the Delta variant and a rising number of younger patients who have not yet been vaccinated.

The new restrictions also mean that private gatherings of three or more people are banned from 6 pm to 5 am. Only two to four members of an immediate family are allowed to gather depending on what time of the day it is, unless they live together or need care.

However, up to 49 relatives are allowed to attend weddings and funerals.

Rallies and protests are banned, although not completely: one-person demonstrations may go ahead.