I think I will always prefer running outside. I enjoy finding new paths to run and basically getting familiar with my surroundings in an intimate way. You can only achieve that on foot. But since I joined the gym, I have been making use of the treadmill (and the exercise bike but that's another post). Initially I thought I would really hate the treadmill--you know, running (sometimes fast) but going nowhere. It turns out that there are some really cool things about the treadmill.
First of all, it allows me to run. This winter has just been brutal and some days I can't go out for a run due to ice or other terrible conditions. Some days I just don't want to deal with the cold (in another post, I'll give a rundown of my cold weather running gear). It was a nice surprise to find out that whether I'm running outside or on the treadmill, I just really like to run. And since I'm in the gym lifting weights three times a week anyway, I've been running more now than in the warmer months. I finish lifting and then I run for 20-25 minutes--I don't have to carve out another special time to go for a run.
Secondly, the treadmill keeps track of my stats: how far I've run, how many calories I've burned, etc. and that's really cool. While I use www.mapmyrun.com to tell me how many miles I cover on a given run, that's the only information I really know when I run outside (since I have not yet invested in a GPS/heart rate monitor watch). It's interesting to know exactly when I hit 2 miles or to push myself to break 300 calories.
I don't have any specific mileage goals but during the warmer months I would run about 6 or 7 miles for my long run and 2-3 for my short. Because of the treadmill, I can still keep my mileage up and also it encourages me to keep better track of my miles (I write everything down right on my NROL4W log sheets). I had always struggled in terms of keeping a training log for my running and while jotting it down on my log sheets is not formal or systemized, I still have a better idea of what I'm doing and how to improve.
Still, I cannot do a long run on the treadmill. I get bored far too easily and then I get antsy. So I've been doing intervals and I have to say, this is a really fun way to use the treadmill. I enjoy trying different interval combinations. Here's a site I found with lots of options. Here is an example of something I've been doing recently which I call 1/2/3/4/recover.
One minute at effort level 1 (an easy pace--you can talk easily, maybe even sing)
One minute at effort level 2
One minute at effort level 3
One minute at effort level 4 (basically sprinting)
One minute to walk it off and almost completely recover
There are many ways to do intervals. You could do hill intervals by changing the incline (which I haven't done yet but look forward to doing). The combinations and possibilities seem to be endless.
Basically, intervals keep it interesting for me. And It doesn't take an hour--after about 20 minutes, I've worked up a sweat and I'm ready to go home and shower. I just couldn't do an hour on the treadmill--the thought of it is even too much for me. But intervals are a quick, effective and fun way to use the treadmill. I may even continue to use it during the warmer months just because, like I said, I'm at the gym anyway.
Oh, by the way, intervals that I control (because some of the treadmills have preset interval programs) are made possible by the Gymboss interval timer, one of the best fitness purchases I have ever made.