CORVALLIS, Ore. - Using fitness DVDs to work out at home may seem like a good way to get started on new exercise goals this year, but those DVDs may also include negative imagery and demotivating language.

A study of 10 popular commercial exercise DVDs showed that the imagery in the fitness videos may be perpetuating and reinforcing hyper-sexualized and unrealistic body images, said Brad Cardinal, a kinesiology professor in the College of Public Health and Human Sciences at Oregon State University.

In addition, researchers found that one in every seven motivational statements on the DVDs was actually a demotivating statement that could reduce the effectiveness of the workout, diminish the user's hope and potentially cause psychological harm, said Cardinal, the lead author of the study.

"These findings raise concerns about the value of exercise DVDs in helping people develop and commit to a workout program," said Cardinal, who is a national expert on the benefits of physical activity. "There are a lot of exaggerated claims through the imagery and language of 'do this and you'll look like me.' "

The findings are being published in the latest issue of the Sociology of Sport Journal. Co-authors of the study are: OSU graduate students Kim A. Rogers, Brian Kuo, Rosalee L. Locklearand Katelyn E. Comfort; and Professor Marita K. Cardinalof Western Oregon University.

Fitness DVDs are a $250 million a year industry but there is no scientific evidence about their safety and effectiveness or the accuracy of the information contained in them, and the industry is largely unregulated, Cardinal said.

For the study, the researchers reviewed 10 popular, instructor-led fitness DVDs, evaluating both the imagery used in the videos as well as the motivational language used by the instructors. The goal was to better understand the visual and auditory messaging and how it might affect users.

Researchers found that most of the instructors and models were slim, female and white, and they typically wore revealing attire. That sends a subtle message about what people who are fit should look like, Cardinal said. This perpetuates objectification of the female body in particular and emphasizes physical appearance as opposed to improved health, he said.

The researchers also found that a quarter of the language used by instructors was motivational, but one of every seven motivational statements was considered negative. Negative statements included phrases such as "say hello to your sexy six-pack," "you better be sweating," and "you should be dying right now."

Those kinds of phrases focus on outcomes, encourage social comparison, and don't take into account individual differences in health or fitness, Cardinal said. "Tough love" phrases and strategies can also have a harmful effect because they can lead to injuries or other adverse health outcomes, he said.

Such messages could be particularly harmful to users who are turning to exercise DVDs to start a new fitness routine or who are uncomfortable in a gym or fitness class setting, Cardinal said. The exercise videos were marketed to novice exercisers while the movement skills tended to be designed for intermediate or advanced levels of fitness, and the instructors' verbal messages sometimes taunted observers to keep up.

"You're inviting into your home these images and messages that could make you feel bad about yourself, and ultimately hinder your efforts to improve your health," he said. "If the experience is not positive, the likelihood the person is going to continue with an exercise program diminishes."

Cardinal urged potential fitness DVD consumers to be mindful of the potential pitfalls of the product when selecting and using exercise videos.

"Buyers should beware when making these purchases," he said. "Remember that we all have different body shapes and styles, and our bodies may respond differently to the exercises being shown. Don't expect to get the same results as what you see on the screen or compare yourself to others."

The findings indicate that there is a need to further study commercial fitness DVDs, Cardinal said. Along with the language and imagery used in the videos, researchers should consider studying the effectiveness and safety of the types of exercises and techniques used, he said. In addition, many of the instructors appear to have little or no credentials in fitness instruction, he said.

"We don't think the videos are very psychologically safe," Cardinal said. "There are also questions about some of the exercises, which could lead to injuries and pose a real danger to the user."