All dogs should be let outside for exercise twice a day, but how strenuous that exercise should be depends, in part, on the size of the dog. Larger breeds need more space to roam so, in addition to regular play in the house or garden, they should also be taken for walks twice a day and these should last for at least 30-60 minutes each.
Smaller breeds often require less of a workout, so letting them out into the garden for a runaround, in addition to their daily walk, can be an appropriate form of exercise. I’d still recommend one daily walk per day; two walks per day would be advisable. The government recommends at least 30 minutes of exercise per day for humans, so this is a good starting point for all fit and healthy adult dogs.
Some breeds, such as border collies, springer spaniels, German shepherds and Siberian huskies, have been bred as "working dogs", so are suited to covering long distances. These types of dogs shouldn’t have any trouble tagging along on a long run, as long as it’s built up as part of their routine