Recent studies indicate that motivation to exercise may be inherited.  This indicates that perhaps some of us are born with a strong desire to exercise while others struggle to find an exercise routine that makes us happy.   

In “Are You Programmed to Enjoy Exercise?,” Gretchen Reynolds writes:

“It’s possible that some of us are born not to run. According to an eye-opening new genetics study of lab rats, published in The Journal of Physiology, the motivation to exercise — or not — may be at least partly inherited.”

For years, scientists have been perplexed by the question of why so many of us fail to exercise on a regular basis when we know we should.  There are many obvious reasons, such as busy schedules and worrisome health complications, but researchers have recently speculated that genetics may play a key role.  In one recent study, sets of adult twins wore activity monitors to track their movements. The results indicated that the twins were more alike in their exercise habits than a shared upbringing alone would explain. The willingness to exercise or not depended a lot on genetics, these studies concluded.  But the specifics on the genes involved and their role in the individuals’ activity remained a mystery.  As a result, scientists at the University of Missouri delved into these issues and created their own groups of exercise and sedentary enthusiasts.  .

They concluded that it is possible that some of us are born not to run. According to this recent study of lab rats, published in The Journal of Physiology, the motivation to exercise or not to exercise may be genetic.  

The researchers accomplished this task by inter-breeding normal rats that had voluntarily run on wheels in the lab. Rats that enjoyed running were bred while those who were more sedentary were bred.  This process continued through several generations, until the researchers had two distinct groups of rats – one group that would happily run for hours on their wheels and others that were content to sit and think about whatever rats think about in their spare time. 

During early stages of the experiments, researchers found some interesting differences in brain activity.  In most situations, the genes create proteins that tell young cells to grow up and join the working world. However, if the genes do not function this way, the cells do not receive the necessary chemical messages and remain in a protracted, stagnant state. These undeveloped cells do not join the cognitive network and do not contribute to healthy brain function.

In general, these genes worked normally in the brains of the rats that are bred to run. However, their expression was quite different in the non-runners’ brains, particularly in a portion of the brain called the nucleus accumbens, which is involved in reward processing. In many animals, including humans, the nucleus accumbens is illuminated when we engage in activities that we enjoy.

As a result, when the scientists closely examined the brains of the two types of rats, they found that the animals bred to run had more mature neurons in the nucleus accumbus than did the non-runners, even if neither group had actually done much running. In practical terms, that finding indicates that the brains of those born to the running line are innately primed to find running rewarding as the more mature neurons in the reward center of the brain could be expected to fire robustly in response to exercise.

Conversely, the rats from the line that is more reluctant to running, with their sparse complement of mature neurons, would probably have a weaker motivation to exercise.

These results may appear to be dispiriting, but the study showed that the brains of those who were less inclined to exercise were changing.  Compared to others in their family that had remained sedentary, those who were involved in the study were responding to exercise in ways that would seem likely to make it more rewarding.

According to Dr. Booth, a leader in the study, that data suggests that “humans may have genes for motivation to exercise and other genes for motivation to sit on the couch.” Over generations, one set of genes could predominate within a family.

The bottom line is that people can decide to exercise, regardless of genetic inheritance.  If you’re not excited to exercise, do what makes you happy and try to “rewrite” your brain so that exercise becomes a pleasurable experience.