There is nothing wrong with running a treadmill. There, I said it. In fact, completing training runs, or just running for fun, on a treadmill can be a great decision! As the weather slowly turns colder over the next few months, the treadmill is a great option for runners who want to stay active over the winter, or who might be training for a race in the Spring.
The greatest benefit of running on a treadmill during the winter is that is much safer! There is no ice, no snow, no potholes, no cars whizzing by, etc. It's always 70 degrees (or close to it) during a run on a treadmill and you can feel comfortable and safe to run as long as you want. Many of our roads in our neighborhoods are not the safest for runners, and I've heard from a number of my running clients who are hesitant to run on certain areas in their neighborhood which is disappointing, but it's the reality. I've also heard of runners suffering terrible injuries running outside in the winter. Where I live in the Northeast, about half of the year the weather stinks and it's not easy to find good footing outside on roads. Why risk life and limb when you can run inside on a treadmill?
Sure, running on a treadmill can feel monotonous but it helps a lot of if you can find a treadmill at a local gym or fitness center or even in your home, that has a TV close by or if that's not an option, find a good podcast (there are lots of good podcasts on running!) and plug in the headphones and enjoy your time away from all of your other responsibilities!
As long as you are using a decent treadmill (that includes pretty much every treadmill in a reputable gym/fitness center), the running surface is easier on your joints, knees, hips, etc. than a road. If you have spent years running outside on the roads this might not be as big of a factor, but if your body has not adapted to years of running outside on the roads, the treadmill is a softer and more forgiving surface than a paved road outside.
A treadmill also gives you a precise pace if you are training with this in mind. If you have a long run for five miles that you want to run at a 9:30 min/mile pace, then go ahead and plug in the speed and hit start! If you are running outside and want to maintain a pace, it can be tricky and involves a lot of looking at your watch, especially if you are just getting used to running at a specific pace.
Finally, a treadmill can help you work on your running cadence, or the number of steps you take per minute. I often speak with my runners on their cadence if they use a GPS tracker that is able to track cadence. A treadmill is a great tool to help practice increasing cadence slowly over time. If you are running on a treadmill, try to calculate your cadence by setting a timer for 20 seconds and count the number of times your feet hit the ground. Take that number and multiply it by three and that is your cadence. Try that a few times to make sure the number is accurate. You know have a base number to use to try and increase and try and work towards 180 steps per minute. It's not a universal rule that 180 is the optimal cadence, but it's something good to shoot for if you are in the 150-160 range.
So while many of us avoid the treadmill, I suggest using the treadmill from time to time, especially when the weather can impact your ability to safely run outside! Keep on running!