I preface the following comments by noting that I am not an athlete, and have never been, and have been technically overweight for much of my adult life, and probably still am.
But riding a bicycle down a hill requires no effort, riding a bicycle on level ground requires no more effort than walking on level ground even though you travel five times as fast, and even if you resign yourself to walking your bicycle up every single hill you're still not engaging yourself in anything more strenuous than walking uphill without said bicycle.
And yet every minute of your bicycle travel you're seeing something new, and every evening you get the benefit not only of meeting people in a new town, but the simple physical pleasure of enjoying a shower, fresh clothes, a meal, and a cold beverage, after a day of heavy exertion.
In short, this may be the easiest thing I have ever done.
Willpower, by contrast, is required only when we ask ourselves to spend time doing things which don't benefit us even in the moment.