What many students fail to realize is that physical activity can have a positive affect on academic performance. Even those that conceptually understand these positive effects may have difficulty pulling themselves away from their books. I was one of those students. It wasn't until the last half of my first year in chiropractic college that I decided to stay committed to my workout routine regardless of the number of exams I was in the middle of writing. Coincidentally, I noticed a boost of 5-10% in my exam marks when I continued to exercise during those high-stress times. The quantity of my study hours was a little lower but they were of higher quality.
There are a number of proposed mechanisms for why these academic/ cognitive improvements are seen with regular physical activity. Increased blood and oxygen flow to the brain, increased levels of norepinephrine and endorphins resulting in a reduction of stress and improvement of mood, and an increase in growth factors that help to create new nerve cells and support synaptic plasticity are some of these mechanisms.
Research in this particular area has steadily increased over the last 10-15 years. The studies in this area are diverse with considerable differences in study methodology, study populations/participants, etc. making it difficult to definitively say that "exercise = improved academic scores". We still don't know if aerobic exercise trumps anaerobic exercise, if team-based sports have the same effect as individual sports, etc.
In a broad sense, all we have at this point is a positive relationship between physical activity and improved cognition. I'm confident that as research continues to be published on the topic, the consistency and strength of this relationship will continue to build.
There is no one-size-fits-all approach with this.
Start small and see what works for you.
Make adjustments as needed.
You may be surprised with what kind of positive affects you've been missing out on!