Lack of physical activity is a risk factor for many serious conditions. The fact that neither adults nor teenagers get as much exercise as they should is, perhaps, not very surprising. But new research shows that the situation might be a lot more worrying than previously believed.

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Teenagers get as much physical exercise as seniors, according to a new study.

The Centers for Disease Control and Prevention (CDC) recommend that adults engage in at least 2.5 hours of physical activity per week.

The CDC also report that only 1 in 5 adults gets this much physical activity. People who do not get the exercise they need are more likely to die prematurely or develop a range of serious illnesses such as heart disease, stroke, type 2 diabetes, depression, and some forms of cancer.

Not only do adults not get enough exercise, but teenagers fare even worse. Fewer than 3 in 10 high school students get a minimum of 60 minutes of daily physical activity, which is the level of exercise recommended by both the CDC and the World Health Organization (WHO).

New research, published in the journal Preventive Medicine, suggests that the situation might be even more grim than previously thought; levels of physical activity among teenagers are surprisingly low, the study finds.

The team of researchers from the Johns Hopkins Bloomberg School of Public Health in Baltimore, MD, set out to examine levels of physical activity across several age groups. Additionally, the research looked at different times of the day and their corresponding levels of activity, as well as differences in exercise patterns according to gender.

The study’s senior author was Vadim Zipunnikov, an assistant professor in the Bloomberg School’s Department of Biostatistics.

Prof. Zipunnikov and colleagues examined a total of 12,529 participants, accessing the data available from the National Health and Nutrition Examination Surveys carried out in 2003-2004 and 2005-2006.

The participants continuously wore tracking devices for 7 consecutive days, taking them off only when they went to bed or had a shower.

These devices tracked how long the participants were sedentary for, and for how long they engaged in light or moderate-to-vigorous physical activity.

The scientists divided the participants into five groups according to age: children (aged between 6 and 11), adolescents (12 to 19 years old), young adults (aged between 20 and 29), midlife adults (31 to 59 years old), and older adults (aged between 60 and 84).

In terms of gender, 49 percent of the participants were male, and 51 percent were female.

Overall, males tended to be more physically active than females, particularly excelling at high-intensity activity.

After midlife, however, physical activity levels in males plummeted, compared with females. In the group aged 60 years and above, males were considerably less physically active, more sedentary, and engaged in less light-intensity physical activity than females.

Researchers found a spike in physical activity levels in only one age group: the 20-something-year-old adults. People in this group tended to be more active in the early morning.

Surprisingly, the study found that teenagers were at the highest risk of being physically inactive, and in their late teens, this group was likely to get as little exercise as seniors.

The study is particularly significant given the high childhood obesity rates in the United States. The CDC report that approximately 12.7 million U.S. children and teenagers are obese.

Activity levels at the end of adolescence were alarmingly low, and by age 19, they were comparable to 60-year-olds. For school-age children, the primary window for activity was the afternoon between 2 and 6 p.m. So the big question is how do we modify daily schedules, in schools for example, to be more conducive to increasing physical activity?”

Prof. Vadim Zipunnikov

Furthermore, the study confirmed that children and teenagers do not meet the WHO’s guidelines for physical activity.

“The goal of campaigns aimed at increasing physical activity has focused on increasing higher-intensity exercise,” explains Prof. Zipunnikov. “Our study suggests that these efforts should consider time of day and also focus on increasing lower-intensity physical activity and reducing inactivity.”

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