Teenagers who increased the days on which they got just 20 minutes of exercise, equivalent to a short walk, were able to cut down on their smoking habit, according to a study.

It also found teenage smokers were more likely to quit altogether if they participated in a smoking cessation/fitness program-and they ramped up the days on which they got at least 30 minutes of physical activity.

"This study adds to evidence suggesting that exercise can help teenagers who are trying to quit smoking," said lead author Kimberly Horn, EdD, the Associate Dean for Research at the George Washington University School of Public Health and Health Services (SPHHS).

"Teens who boosted the number of days on which they engaged in at least 20 minutes of exercise, equivalent to a short walk, were more likely than their peers to resist lighting up a cigarette," the researcher stated.

Horn and her colleagues tracked 233 teenagers from 19 high schools in West Virginia, a state with among the highest smoking rates in the nation. The participants in the study were daily smokers with other risky behaviors.

That study found that an intensive smoking cessation intervention combined with a fitness program was the most successful way to help teenagers quit.

In the current study, Horn`s team looked to see if an increase in physical activity would help teens quit regardless of the type of intervention. In this study, as in the previous one, some teenagers went through an intensive anti-smoking program combined with a fitness intervention while others just got the smoking cessation program and still others listened to a short anti-smoking lecture.

Horn found that all of the teens increased their exercise activity to some degree-just by virtue of being in the study. However, teens who reported increasing the number of days in which they got just 20 minutes a day of exercise were able to significantly cut back on the cigarettes they smoked.

Horn`s previous study showed that the most powerful way for teens to quit smoking was if they participated in a program called Not-On-Tobacco; it was even more powerful for boys with an added fitness component. The researchers believe that the 20-minute threshold for changing smoking behavior deserves further study.

But Horn noted that the study has limitations.

"We don`t fully understand the clinical relevance of ramping up daily activity to 20 or 30 minutes a day with these teens. But we do know that even modest improvements in exercise may have health benefits. Our study supports the idea that encouraging one healthy behavior can serve to promote another, and it shows that teens, often viewed as resistant to behavior change, can tackle two health behaviors at once," she added.

And researchers still do not know the mechanism that might explain the findings. However, she says that physical activity is known to spur the release of the body`s feel-good chemicals called endorphins.

One possible explanation is that those substances might help teen smokers better deal with the cravings or weather the withdrawal symptoms that often lead to relapse, she said.

The study appeared online in the Journal of Adolescent Health, the official publication of the Society for Adolescent Medicine.