Going for a bike ride today and find running is a pretty high impact sport. Many runners have injuries with their knees, feet or legs from the repetitive impacts. Plus, in running you have to carry your own weight so unless you are pretty thin, running can be mighty tough - this is why so many competitive marathoners look like they are starving to death.Cycling is low impact and weight bearing. Even very big people can cycle. And cycling like running can burn a bunch of calories which makes it good for weight loss. Cyclists can also put in far more hours than other athletes (low impact again) which allows high mileage cyclists to burn more calories.But with running you only have to run 20 min and for biking you have to bike an hour or you have to bike 7 miles and run 1mile to get the same results in biking. Run Smart.