Mentally, you may have a tougher time dealing with the monotony of the treadmill. It’s easier to distract yourself when running outside. The bottom line: If you’re training for a specific outdoor race, try to train outside as much as possible to get prepared for race conditions.
What’s the Difference Between Running on a Treadmill and Running Outside?
Running on a treadmill feels somewhat easier physically because the ground is being pulled underneath your feet and there’s no wind resistance. Running outside demands more from your body because you’re propelling your body forward stride for stride. Many treadmills are padded, making them a good option if you’re overweight or are injury-prone (especially with knee issues) and want to decrease the impact. You can better simulate outdoor running by setting your treadmill at 1% incline.