Yes, you can watch a movie while running on treadmill. There are a few things you need to take into account though to make sure it's enjoyable and safe.
First, the position of the treadmill belt and your body in relation to the television screen is important. If the belt is too low, you'll have to hunch over to see the screen, which can be uncomfortable and even dangerous if you lose your balance. If the belt is too high, your head will be tilted back at an awkward angle for extended periods of time. Positioning the belt so it's at about waist level is ideal.
Second, consider how fast you're running when deciding what type of movie to watch. A slow-paced film or tv show might not be as engaging if you're moving quickly; conversely, an action-packed thriller could be overwhelming if your heart rate is already elevated from running at a moderate pace. Choose something that matches your current energy level for best results.
Finally, use caution when reaching for the remote control or any other objects while on the treadmill; remember that you're in motion and losing your grip could cause serious injury. With a little planning and common sense, watching a movie on a treadmill can be safe and enjoyable!