Sitting at a desk burns very few calories. It can be difficult to fit exercise into your schedule when you're working on a homework deadline. If you are willing to plan ahead a little and shake up your routine, exercise can help clear your head and improve your academic work as well as prevent the weight gain that often plagues students. Keep in mind that even very short bouts of activity add up, so you don't necessarily have to commit to a 60-minute run or a trip to the gym.
Take activity breaks. Every 20, 30 or 60 minutes make a habit of putting down your pencil and doing a short burst of activity. Try 60 jumping jacks. Do 20 squat thrusts, where you jump down into a plank position and then jump back into standing position repeatedly.
Take advantage of podcasted lectures. Some professors offer MP3 recordings of their lectures, or you can record lectures during class and take them with you on a run or in the gym. You may be surprised how much more information you retain from a lecture on your afternoon run than you do sitting in the classroom.
Take your reading to the treadmill. If you've got a long reading assignment that doesn't require writing, read it on the treadmill, elliptical trainer or stationary bike. If you're going to the gym, it may be helpful to take earplugs or a music player to drown out the distractions around you.