Studies also show that exercise is also how we energize our brains. Biologist John Medina's book, "Brain Rules: 12 Principles for Surviving and Thriving at Work, Home, and School," points out that being on the move helps us think more productively. But what happens when exercise burnout strikes? Several studies have found that what leads to exercise burnout includes boredom, too little time, or too many competing obligations that push exercise off the high-priority list.

Here are seven tips to beat back exercise burnout:

1. Vary your routine. Choose working out on the stretching machines one day and then pick weights the next. Skip one day of aerobic exercise for a weightlifting session. Varying your routine staves off boredom, while also exercising different muscle groups. Make a weekly list of varying exercise routines.

2. Vary exercise times. Exercising at the same time of day can lead to boredom. The same exercise routine can also backfire if competing obligations take over that time frame. You can be flexible about when you exercise and even how long you spend exercising. Break up your practice of a 30-minute morning workout into two smaller workouts, one in the morning and one toward the end of the day.

3. Take an exercise class. Take an exercise class to vary your exercise routine. Gyms and local community centers offer classes. Choose the one that fits your budget, because you don't want money to become a reason to avoid exercise. Exercise videos also can be a lively way to change your routine

4. Exercise with a friend. Mingling with others and chatting while you exercise with other exercisers at the gym or when you go on walks keeps you interested. Feel free to share your ideas for changing the routine and you can get creative about changing your schedule if other obligations arise.

5. Don't skip a good night's sleep. A lack of adequate sleep can play a strong role in exercise burnout, because exhaustion creates stress, fatigue and a lack of focus. A lack of focus can also lead to exercise injuries. Ease into a good night's sleep by avoiding exercise late at night.

6. Stretch. Stretching exercises before, during or after your exercise routine will keep you limber and less likely to experience minor exercise injuries. If you find yourself working late, take a standing or stretching break to do a few exercises in your office before you get back to work.

7. Take an exercise break. A break from exercise will help you steer clear of exercise burnout. Take a day or two off, and call it an exercise vacation. You'll return to your routine stress-free, rested and re-focused, and if you return to your regular regime, your fitness won't suffer.