The only problem with treadmills as opposed to outdoor or track running is the impact it has on a lot of peoples joints. People with knee or ankle or hip injuries are highly advised not to use a treadmill. I am not sure what you mean about the long distances part as it really depends on your fitness ability. However, you will burn about the same amount of calories however far you go even though it will take less time the faster you go or more time the slower you go. IE 3 miles is 3 miles burned whether walked or ran, etc. Ofcourse the different types of activities from walking or running will utilize either more of a fat burn or muscle work. A great way to build up endurance is by intervaling your running and walking. For example, start out running 4 mins, walking 1 for a total of 30 mins. Over time you can get down to like 9 mins run 1 min walk and then 14 plus a minute walk, until you can run the whole thirty. Clients i have training for triathalons or like 5k runs I usually suggest this to help build a runners endurance. Walking and running will also develop muscles in different ways depending on which one you are doing. It really depends on your fitness goals and your current ability. As far as a treadmill every day? I would try and avoid it due to the impact, though norditrac has come out with a few new models with shock absorbers. Otherwise try the ellipticals or tracks or town lake as well!
Whitney Denise

George TabaresFitness Specialist/Eastern Bodywork
Running injuries generally occur when there is a preexisting condition. This can be due to old injuries, a lack of flexibility, improper running shoes, faulty running surfaces, or combination of each.
"Long distances" are relative to the person's inherent abilities and current fitness status.
Power walking is very effective for burning fat and minimizing muscle loss. Running at a long slow pace is great for burning fat. Running at a sprint speed will utilize extra calories from carbohydrates thereby using them before they are stored as extra weight, and sprinter's never lacks muscle tone. Last but not least are intervals which tend to have benefits from both sides of the equation; fat burning, carb utilizing and muscle tone maintenance.
Enjoy your next run.