Barkley and Lepp were interested in the relationship between smartphones and fitness levels because, unlike the television, phones are small and portable, therefore making it possible to use them while doing physical activity. But what the researchers found was that despite the phone's mobility, high use contributed to a sedentary lifestyle for some subjects.

More than 300 college students from the Midwest were surveyed on their cell phone usage and activity level. Of those students, 49 had their fitness level and body composition tested. The researchers' results showed that students who spent large amounts of time on their cell phones -- as much as 14 hours per day -- were less fit than those who averaged a little more than 90 minutes of cell phone use daily.

One subject said in the interview data: "Now that I have switched to the iPhone I would say it definitely decreases my physical activity because before I just had a Blackberry, so I didn't have much stuff on it. But now, if I'm bored, I can just download whatever I want."

The study is believed to the first to assess the relationship between cell phone use and fitness level among any population. Barkley and Lepp conclude that their findings suggest that cell phone use may be able to gauge a person's risk for a multitude of health issues related to an inactive lifestyle.

The study appears online in the International Journal of Behavioral Nutrition and Physical Activity.