We all know exercise is important for physical health. However, it has a number of surprising cognitive benefits that help improve things like focus, memory, stress management, decision-making, and even brain regeneration. Here is the how and the why of it, and why you should implement exercise into your routine to enhance productivity.
Primary cognitive benefits
Dr. John J. Ratey, professor of psychiatry at Harvard University, posits that the intellectual benefits of exercise are threefold . First, he explains that exercise "optimizes your mindset to improve alertness, attention and motivation." Second, it "encourages nerve cells to bind to one another," the cellular basis for the uptake of new information. Finally, exercise "spurs the development of new nerve cells from stem cells in the hippocampus". This means that exercise helps prepare the brain for learning and also primes it to retain information more easily.
How exercise can improve decision-making
Studies have shown that aerobic exercise activates the part of your brain involved in executive function, which helps with planning and making important decisions. A study published in 2016 found that participants who took the Stroop Test (a measure of executive function) following ten minutes of repeated short sprints performed better than they did when rested.  They also achieved better results when tested 45 minutes after completing the sprints, compared to when rested. This suggests that taking a short burst of intense aerobic exercise can help improve decision-making in the time after.
Exercise and brain mass
Did you know that humans start losing brain mass from the age of 20?  One of the keys to maintaining brain mass is to push yourself past the comfort zone - physically as well as mentally. Studies have found that, in healthy young men, as little as 20-30 minutes of aerobic exercise can increase serum BDNF (Brain-Derived Neurotrophic Factor), a growth factor involved in growing new brain cells and in allowing existing brain cells to survive . Exercise therefore is a weapon you can use to combat brain atrophy and stay at your sharpest.
The effect of exercise on short-term vs long-term recall
If you're trying to prepare last minute for a test or presentation and you're trying to learn your notes, going for a run prior may help. Biomedical scientist Dr. Rhonda Patrick shares research suggesting that if you run before you try to learn something, it will improve your short-term recall (ibid.). But if you're trying to learn something and you run afterwards, you're more likely to remember it the next day or later. So, running before or after you learn something can help engrain it in your short- or long-term memory.
The relationship between exercise and mental hygiene
Whilst it is clear that exercise directly aids the processes of learning and information recall, its effect on overall wellbeing can improve workflow too. Stress is a problem for many people: at school or work we are often faced with high-stake assessments, whether it be exams, presentations, projects, etc. It is well-documented that exercise has overwhelmingly positive effects on stress management, which is crucial to developing a sustainable approach to work or studying. Specifically, exercise reduces levels of stress hormones adrenaline and cortisol, which helps to alleviate both the physical and emotional symptoms of stress.
Furthermore, people who suffer from poor mental health in the form of depression or anxiety can help themselves through exercise. It can be very hard to motivate yourself to work when you're suffering from a bout of severe mental health, but there is hope: exercise is shown to release endorphins in the brain as well as raise dopamine levels, both of which improve mood and attentiveness.
Exercise and sleep
A sleep schedule filled with regular and restful sleep is essential to maximising productivity and mental sharpness. Exercise can improve our quality of sleep: National Center for Biotechnology Information assert that "exercise is a strong entrainment signal for mammalian circadian clock", meaning that exercise helps regulate our bodies' recognition of when we should be awake and when we should rest, helping to improve energy during the day and restfulness during the night.   In addition, exercise reduces cortisol levels during the night, helping us wind down and fall asleep easier. 
The bottom line
Exercise has a multitude of benefits for our bodies and brains. It is worth finding time in your routine to include it, not just for your general health, but also because it could give you an edge to enhance your learning and take your work to the next level.