I cycle twice a day with my dog Bosun on an extension waist lead. He is a very active Bearded Collie cross with chase and behaviour issues so can't go off lead - given he needs about 10-15 miles a day of running this is the only way I can keep him fit and healthy. For him it is the morning/evening patrols and he sees it firmly as his 'job'.
After a few offs in the early months, he's become an expert at pacing alongside, anticipating which side to cut as we overtake and which side of the bollards etc I am going to go. When he is working he simply ignores all distractions - squirrels under the nose, cats in the way, rats by the river, and all the other inquisitive or barmy dogs who want to have a go. On a mission. Off the bike - he is a menace. He was in the last chance saloon after an incident with a horse rider in Richmond, and the cycling has effectively saved his life. It was the suggestion of the top (most expensive) dog behaviourist in the UK after vet and other behaviourist consultation. Still got a lot of work to do but he may yet make it to old age.
Every few weeks I get someone tell me I am being cruel to the poor animal, and I am a lazy irresponsible so and so etc. I respond by asking exactly what their professional qualifications for the allegation are in case they have something useful to say - not yet - and then they get the full works. I then spend the day feeling bad.