University of Wisconsin researchers have found that the same cravings for food, drugs and sex are related to the desire to exercise and have found evidence for exercise addiction in mice.

University of Wisconsin researchers studied the exercise patterns of two sets of mice, one group comprised of normal laboratory mice while the second group included mice that had cultivated a tendency for wheel running over 29 generations. The study was planned to find changes in brain activity, and both groups were given the option of whether to run.

The study showed that the same brain area in mice that is stimulated by cravings for sex, food or drugs is also stimulated by running. For six days the two groups of mice were allowed to run on the wheels, but on the seventh day, half of the mice from each group were denied access to the running wheel. The mice that were denied the ability to run had higher levels of neuronal stimulation than those who had run on the wheel.

“These mice have run for six days,” Stephen Gammie, an author of the study, explained. “They want to run, and they’re ready to run, but they can’t. Change in brain activity is an indication of their motivation to run.”

Researchers believe the ability to run in humans may be an addiction that cannot be easily cut off. Humans can get what is called “runner’s high.” When exercising, the brain releases neurotransmitters, called endorphins that can cause a feeling of euphoria. Prolonged exercise such as running can cause a burst of this euphoric feeling.
“There are plenty of people who become ‘addicted’ to running because of the endorphine release they get,” UW faculty associate of kinesiology Kristine Hallisy said.

UW sophomore Emily Kanarek said she likes the effect that exercise has on her. “Exercise makes you feel good, and because of that, it makes you want to do it more and more,” she said.

People can often become so attached to exercise that when physical activity is taken out of their daily routine, either from injury or heavy workload, a sense of loss may occur. They can become depressed, because their normal release of stress has been taken away, and they are not releasing as many endorphins as they are accustomed to. A sensory that goes through the human brain when exercising also affects emotions. Hallisy said if people are not allowed to exercise, it may take an emotional toll on them.

Exercise can also take a physical toll if it is done too much. Over-exercising makes microscopic tears in the body’s tissues that can cause serious injuries, hurt performance in other activities and cause a lot of pain.
“Everything should be done in moderation,” Hallisy said.

UW sophomore Jeff Cohn said he thinks that people need to be careful when exercising. “If the person is exercising on a normal healthy workout there is nothing wrong with it. If the person is doing it more then their body can physically handle, however, then there is a problem,” he said.