Image copyright EPA Image caption Social distancing rules mean people should stay at least 2m (6.5ft) away from each other

There's now a new phenomenon - known as "quarantine shaming" - to try to keep people indoors.

Over the weekend, photos of busy parks, markets and beaches in the US, UK and Canada caused uproar, as officials described people who ignored social distancing guidelines as selfish, arrogant or self-destructive.

On social media, some have been even more critical - the hashtag #COVIDIOTS has been trending, and people have criticised individuals seen at public gatherings, or posted that they "deserve to get the virus".

In the UK, one man posted an expletive-laden rant as he live streamed people walking on the seafront by his house - in a video that went viral.

Social psychologists say that shaming plays a significant role in enforcing social norms - especially at a time when norms are rapidly changing as a result of coronavirus.

But social distancing outdoors can also be difficult - especially when there is contradictory advice about where to go, and you can't predict how others will behave.

So what's the best way to stay safe - and avoid a public shaming - while exercising outdoors?

Can I still go for a walk?

The official advice can be confusing. On one hand, we've been told to stay home as much as possible. On the other hand, we've also been told that it's important to keep exercising - and that a walk or run in the park is OK.

In New York, the city parks commissioner Mitchell Silver encouraged residents to use the city's large number of parks, pointing out that spending time outdoors can reduce stress and boost the immune system.

Similarly, UK PM Boris Johnson has stressed that parks and open spaces are "crucial for our country and for our society", and urged people to use them responsibly.

Image copyright Getty Images Image caption Spending time in parks and green spaces is good for your physical and mental health

But when the parks become too popular - or people start gathering there in groups - it gets problematic.

Over the weekend, police in Seattle had to use loudspeakers at a park to remind people to keep 2m (6.5ft) away from each other, while in the UK, some parks, beaches and open spaces were packed over the weekend, leading to the government announcing greater restrictions on Monday.

The Stranger, a news site in Seattle, published a blog post with woodland trails for solo hikers - but decided to take down the post a day later, after learning that people were hiking and gathering at some of the trails in large groups.

And in Canada, beaches in Vancouver and Toronto were busy - even as some of the streets were quiet - prompting Prime Minister Justin Trudeau to warn people were "putting everyone else at risk".

Image copyright Reuters Image caption The more people there are at a park, the harder it becomes to socially distance effectively

Brian Labus, a professor in public health at the University of Nevada, Las Vegas, stresses that you have to treat "going outside as a risk every time you do it".

But, he adds, there are ways to reduce the risk to close to zero if you plan your trip carefully.

"If you're outside walking by yourself, you're not exposed; if you're out walking the dog by yourself, there's no risk… it's when you have contact with other people that you need to be concerned."

Running or cycling as a group - and running past others - is a no-go, due to the need to maintain a 2m distance at all times.

"If you're running past somebody and they sneeze, that's going to land on you. It doesn't matter how fast you're running - you can't outrun a sneeze," says Prof Labus.

Instead, he recommends runners and cyclists "look ahead", and pace themselves where necessary, so they can work out how to keep a distance between themselves and others on the street.

It's also important to think carefully about where you go - and prioritise avoiding crowds.

"As soon as there are large numbers in a park the risks go up," he says, as it becomes harder to maintain a 2m distance with everyone.

"Just having a bunch of people there makes it tougher to keep that distance," especially as entry points, like park gates, could get busy.

Instead, he recommends individuals "don't go where people tend to congregate", but walk through quieter places, like their own neighbourhoods.

What's the etiquette for social distancing when you leave home?

Image copyright Getty Images Image caption It's hard to social distance properly in a lift

The outbreak has also thrown up all sorts of new social dilemmas. If you pass someone when you're going for a walk, how do you greet them? What do you do if you meet someone on a narrow path? And what about if someone wants to get into a lift with you?

Lizzie Post is co-president of the Emily Post Institute, which has recently published guidelines on the etiquette of social distancing for coronavirus.

She says "our manners look really different right now", but the core principles of "consideration, respect and honesty" are still the same.

"When I walk my dog in my neighbourhood, if someone's coming and I don't see them moving, I move off on to the grass, or I'll wait in the driveway for them to pass."

Media playback is unsupported on your device Media caption 60 days of coronavirus in the US - in 60 seconds

She acknowledges that this would feel rude in normal circumstances - but urges people to overcome any feelings of awkwardness.

"The big way to communicate you're not trying to be rude is to still make eye contact or smile - or explain you're 'just social distancing'."

"All the experts say that the more you can respect the idea of physical distancing, the better off you'll be."

On narrow walkways, "you can certainly turn your face away from someone if you have to pass them in close quarters." Alternatively, she recommends treating it like a single lane bridge, and waiting for the other person to pass before you go through.

Image copyright Reuters Image caption Don't be afraid to walk on the grass to avoid others

And if someone tries to follow you into a lift?

Ms Post admits she would "probably just hop out and let them take the lift", or try to explain "I'm trying to social distance, do you mind waiting for the next one?"

"It'll feel a little awkward, but I think over time, they'll realise that you were just trying to practise good habits."

Does public shaming work?

Public shaming can be complicated - and controversial.

In recent years, some people who have been subjected to public shaming online have faced what's been described as digital "mob justice", even losing their jobs or receiving death threats.

Image copyright EPA Image caption Some pubs and bars stayed open on St Patrick's day

While there haven't been widespread reports of extreme online shaming over coronavirus, some individuals who have come under fire have said they felt unfairly targeted.

One Irish pub owner in Pasedena, California, faced heavy criticism for opening his bar on St Patrick's Day, attracting a crowd - and the ire of local residents.

Joseph Griffin told the LA Times that he had asked customers to only order takeaway or deliveries, and that he was not aware that the city had ordered all bars to close the day before.

"To have people call me and my business out online so viciously - in some cases, to have people screaming at me and the employees of this bar - was incredible."

However, experts say that shame can also be effective in establishing new social norms - and that the coronavirus outbreak is a particularly good example of where it is needed.

Media playback is unsupported on your device Media caption US students on spring break defy COVID-19 warnings

"Shaming should not be used for a problem that does not concern the audience," says Jennifer Jacquet, an environmental studies professor at New York University.

However, "coronavirus is a problem that affects all of us - a problem with severe and immediate repercussions, where we're all expected to make sacrifices… it's a true co-operation dilemma."

Prof Jacquet, who has written a book about the use of shame in encouraging co-operation, thinks this tactic has been used effectively to discourage people from hoarding supplies or flouting social distancing rules.

She believes shame can even be deployed effectively against institutions - for example, if governments are failing to enforce social distancing rules, or behind on providing coronavirus tests and protecting healthcare workers.

"I hope shame will really shine as a tool that can be used for social good."

Ms Post argues that bad behaviour can be called out in a respectful manner. For example, rather than calling those in busy crowded places "crazy" or "stupid", it's much better to raise concerns in a civil way that invites a conversation and focuses on solutions.

"We know tone matters because people feel it. If you call them names and criticise their mental wellbeing, it's very attacking behaviour."

Meanwhile, Daniel Sznycer, a social psychologist at the University of Montreal, says that shame can deter certain behaviours - but cautions that there are limits.

Shame is essentially about "reputational damage" and social norms, he says, which means that some individuals could feel ashamed about a particular behaviour - but continue to carry it out in secret.

Going outdoors is an "inherently public" act, so people who have been shamed are more likely to comply with social distancing rules, he argues.

However, shame might be less effective with behaviours that can take place behind closed doors - for example, if someone uses online shopping to stockpile supplies they don't need.

Prof Sznycer argues that "guilt - an emotion when you realise you've harmed people you love" - tends to lead to "more stable, benign and reliable" behaviour change.

"It may be that a government prompt about caring about the welfare of others could be more effective than shame," he says, although "for guilt to work, you need to value the welfare of others to begin with."