It is a question that has bedeviled physicians, nutritionists and trainers for generations: Why do some people hit the gym every day without fail, while others can barely find the motivation to hit the restroom in the morning?

Now scientists may have found a clue. A new study in the Journal of Physiology suggests genetic loading may influence the level of activity in which most of us engage on a daily basis. A rat study suggested that identical twins have a tendency to exercise a similar amount no matter what environment with which they are faced. Researchers then bred rats that were inclined to be highly active, and a separate group inclined to be more sedentary. Once again, the rats did as their genes predicted:

Even so, Dr. Booth said, his group’s data would seem to suggest “that humans may have genes for motivation to exercise and other genes for motivation to sit on the couch,” and over generations, one set of these genes could begin to predominate within a family. But predispositions are never dictatorial.

The silver lining in this particular study, however, is that rats who spent more time sedentary soon began to mimic their active counterparts; studies indicated that their brains actually began to look more like their motivated cousins across the lab. It seems possible that you, too, can raise your energy level just by, well, raising your energy level.  Just say to yourself “I will do it!”  Get out there and move!

We have plenty of hard data that tells us exercise can prevent knee pain and back pain, and prevent costly orthopedic knee surgeries. This study should be a strong reminder that exercise is a choice we can all make when necessary.