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UC Davis Health System

UC Davis Health System

Researcher pinpoints barrier to maintaining training programs among middle-aged non-exercisers

Photo of woman jogging on treadmill This study notes that lack of an increase in vigor and a decrease in fatigue among adult non-exercisers may contribute to the difficulties they have in maintaining a regular exercise program.

Middle-aged non-exercisers enjoy far lower levels of mood enhancement from aerobic exercise than do their counterparts who exercise regularly, according to a new study by a researcher from the Department of Veterans Affairs and UC Davis Health System. The finding may explain why this population so often has difficulty initiating and continuing new training programs.

"The lack of an increase in exercise-induced vigor or related mood enhancement factors among adult non-exercisers may contribute to the difficulties experienced by these people in maintaining a regular exercise program," said lead author Martin Hoffman, chief of Physical Medicine and Rehabilitation at the Department of Veterans Affairs, Northern California Health Care System in Sacramento, Calif. Hoffman also is a volunteer clinical professor in the UC Davis Department of Physical Medicine and Rehabilitation.

Hoffman said, "Trainers would be wise to share this information with those who are initiating an exercise program so that they may be more likely to persist through the initial phases of the program."

The study, published online in the February issue of the Archives of Physical Medicine and Rehabilitation, is unusual for its focus on middle-aged non-exercisers rather than the young, fit population that is the norm for exercise-related studies. Also, few studies have been conducted comparing exercise-induced mood alterations between regular exercisers and non-exercisers.

Hoffman analyzed pre- and post-exercise responses to mood-related questions among three groups — non-exercisers, regular-to-moderate exercisers and ultra-marathon runners — consisting of eight men and eight women in each group. Participants were aged 28 to 59, with a mean age of over 40 for each group.

Participants completed a Profile of Mood States both before and after 30 minutes of treadmill exercise. The profile measures mood states through a list of 65 adjectives for six dimensions of mood, including tension/anxiety, depression/dejection, anger/hostility, vigor/activity, fatigue/inertia and confusion/bewilderment. The exercise involved walking or running at the individual's self-selected speed, corresponding to a "somewhat hard" effort for 20 minutes, preceded and followed by five minutes at a "very light" level.

Photo of Martin Hoffman"The lack of an increase in exercise-induced vigor or related mood enhancement factors among adult non-exercisers may contribute to the difficulties experienced by these people in maintaining a regular exercise program."
— Martin Hoffman, study lead author

The most striking results were changes in vigor and fatigue. The study found that the aerobic exercise session resulted in an increase in vigor and a decrease in fatigue among the ultra-marathon runners and regular moderate exercisers. In contrast, non-exercisers showed no improvement in these scores. Although total mood disturbance improved in all three groups after exercise, the two groups of exercisers showed approximately double the effect of the non-exercisers.

The lack of an increase in vigor and a decrease in fatigue among adult non-exercisers may contribute to the difficulties they have in maintaining a regular exercise program, the study states. The study recommends conveying such information to this group so that they may increase their chances of persisting through the initial phases of an exercise program.

"Obesity and inactivity come at a high societal cost," said Hoffman. "Additional knowledge on how to help people be more active can help tremendously. This study predicts and pinpoints a previously unidentified barrier to initiating new exercise programs in middle-aged adults. That information can in turn be used to help these non-exercisers continue through the initial phase of new training programs, when so many are inclined to drop out."

To what degree can post-exercise mood changes be attributed to what is known as an "endorphin rush"? This term has been adopted in popular speech to refer to feelings of exhilaration brought on by pain, danger or other forms of stress, supposedly due to the influence of endorphins. However, this term does not occur in the medical literature, and for good reason, Hoffman said.

"To document a runner's high or endorphin rush directly, we would have to conduct invasive post-exercise analysis of spinal fluid," he said. "Such testing simply isn't practical on human subjects, and indirect evidence has so far been inconclusive. Thus, the concept that post-exercise mood changes are induced by specific biochemical compounds circulating through the nervous system necessarily remains hypothetical and anecdotal for now."

Potential future research includes longitudinal studies of non-exercisers willing to follow a closely monitored conditioning program over several weeks to determine whether their post-exercise Profile of Mood States responses change over time in favor of increased mood enhancement. If those responses continue to be limited, further investigation of a genetic basis for a blunted mood enhancement from exercise might be in order.

Hoffman and co-author Debi Rufi Hoffman self-funded the current study, which supports the latter's doctor of psychology studies at the California School of Professional Psychology, affiliated with Alliant International University in Sacramento, Calif.