Should we be wearing masks while exercising? Jacinda Ardern, Ashley Bloomfield respond to confusion

With the whole country under a snap alert level 4 lockdown this week after cases of COVID-19 were detected in the community for the first time in months, many of us are back to our old lockdown exercise regimes: Walks around our neighbourhoods accompanied by kids on scooters or bikes, or runs up local mountains. 

Prime Minister Jacinda Ardern announced on Wednesday compulsory mask use for New Zealanders aged 12 and over while visiting essential services currently open during alert level 4 like supermarkets, pharmacies and service stations. 

But some confusion has reigned over whether we should be donning masks while exercising outdoors on walks and runs, especially if practising social distancing from others.

Now we know: You don't have to wear a face mask during strenuous outdoor exercise, but you must practice physical distancing of at least 2m from others during these times.

In Thursday's press conference, Ardern and Director General of Health Ashley Bloomfield addressed the uncertainty. 

"We have not mandated mask use for exercise outdoors in level 4 - our general advice is when you go out, wear a mask," said Ardern. 

"But we also want to be practical about [it]... someone, for instance, may be engaging in a very strenuous run where wearing a mask might become difficult - I couldn't speak to personal experience [on that]." 

Ardern said in "those circumstances" practising "good, decent social distancing" is a must. 

"We know from other countries with Delta that just walking past  someone is a risk," she said.

"So generally when you leave the house, wear a mask...but we will be practical there."

Bloomfield pointed to the recent investigation into a case of COVID-19 transmission at Auckland's Jet Park quarantine facility, which was likely caused by room doors being opened simultaneously for just seconds at the same time.

"So we know it can be a very transient exposure," he added.