What is the safest way to get some exercise without exposing yourself to the danger of being infected with the coronavirus or infecting others, in case you unknowingly have it?

Jogging outside ?

Order two adjustable dumbbells, a bench and mat from Amazon (around 12,000) and work out in your home. That's what I did after the setsuden following Fukushima when the gyms shut down. The best 12,000 yen I've ever spent, as I still work out on this gear 3 times a week.

For cardio, on the weekend, take a train (which are fairly empty now) and head to the nearest hills for a day hike. Sorted!

Walk, hikes, runs, while keeping 2m from others. Takes some fast moves in urban areas, but it can easily be done. What a weird question at this point though when the streets are still busy enough.

Back in the 60s, 70s, and 80s Jack LaLanne had a TV show where he exercised all the muscle groups and aerobic exercise using a chair. One chair. In one place. No expensive equipment or club memberships required.

https://www.youtube.com/watch?v=y4A3mdG5zbQ

Lots of usable props inside one's home can help with that. When it's raining, I stay indoors and use my stairs for incline and decline pushups and for walking/running or just walk in place. You can also fill a bag with clothes to use as dumbbells, do captain's chair sit-ups and other core exercises without the need of gym equipment, and a whole host of other exercises. All you need is a little imagination and willpower.

These are pretty good ...

https://www.youtube.com/watch?v=FRDGlIJTVt8&list=LLzoKxKtVssDcNRhrv-gsJGQ&index=7&t=0s

https://www.youtube.com/watch?v=2DNioliqOug&list=LLzoKxKtVssDcNRhrv-gsJGQ&index=6&t=0s

What is the safest way to get some exercise without exposing yourself to the danger of being infected with the coronavirus or infecting others, in case you unknowingly have it?

The question misses one crucial point: to find a way not to endanger neighbors/others in case you already got infected without symptoms.

Solo workout at home or in open spaces is reasonably safe. Boredom may be solved with mobile devices. Though it has yet to come into my mind, we can be more creative to do something both fun and safe/healthy.

Jog and street workout. Solo rub and tug.

Switch on the computer and go to

https://www.youtube.com/user/TheWeightSaint/videos

He's back! You choose.

Walking and cycling but keeping two metres apart.

500ml beer curls.

Two basic types here. Upper body workout with dumbbells or equivalent. For the legs there are any number of country walks around this area, of different shapes and lengths, including the option of a quick nip up 250 stone steps to the local Jinja. Don't have to meet anyone, but I do keep a mask in me pocket for just in case.

Another vote for cycling...

If you are interested in calisthenics there are many prison workouts you can do in your home. I think they center around the burpee as well as pushup and pullups.

As zichi said it is dependant on location. If you are in a densely populated area, exercising out side and maintaining a safe distance from everyone else trying to do the same can be difficult if not outright impossible. In which case all the tips above for indoor exercise are the best way forward. If you live in the country then yes it is a lot easier to exercise without interacting with other people, walk the dog or what ever. If at all possible getting out of the house, even in to the garden is recognised as beneficial to your mental wellbeing, but not everyone is in a position to do that which is why there is considerable concern among mental health professionals in country’s with strict lock downs.

For cardio, on the weekend, take a train (which are fairly empty now) and head to the nearest hills for a day hike. Sorted!

I'd avoid all trains unless you live in the countryside or actually need to use one.

You can just walk around your neighbourhood and keep a safe distance (~2m) from other people

Exercise in your home, obviously.