Key takeaways:

More sedentary time during childhood was associated with higher cardiac work in adolescence.
Clinicians should encourage physical activity among children and explain the risks of too much sedentary time
Moderate to vigorous physical activity during childhood was associated with less cardiac work during adolescence, according to study findings published in the Journal of the American Heart Association.

Researchers also found the reverse was true — increased sedentary time during childhood led to greater cardiac work in adolescence.

“We expected that physical activity would have beneficial associations with cardiac work,” Eero A. Haapala, PhD, a pediatric sports and exercise medicine researcher at the University of Jyväskylä in Finland, told Healio. “Therefore, the findings regarding sedentary time are alarming, if not unexpected or surprising, as children and adolescents spend increasingly long periods of time being sedentary.”

Researchers evaluated data from 153 participants aged 6 to 8 years at baseline (median age, 15.8 years; 69 girls) from the Physical Activity and Nutrition in Children study, which looked into children’s physical activity and diet in a city in Finland.

Participants wore a combined accelerometer and heart rate monitor to track physical activity, and researchers followed up with them at 2 and 8 years, calculating cardiac function at the latter timepoint with impedance cardiography. Adjusting for age and sex, the researchers analyzed the data with a linear regression analysis.

Researchers found negative associations between cardiac work at 8-year follow-up and cumulative moderate to vigorous physical activity from baseline (standardized regression coefficient [beta] = –0.323; 95% CI, –0.527 to –0.119) and cumulative vigorous physical activity (beta = –0.295; 95% CI, –0.508 to –0.083), with a similar association found for cumulative vigorous physical activity when looking at cardiac work index at 8-year follow-up (beta = –0.218; 95% CI, –0.436 to 0).

In contrast, cumulative sedentary time was positively associated with cardiac work after 8 years (beta = 0.245; 95% CI, 0.092-0.398). However, researchers noted adjusting for body fat percentage attenuated this association (beta = 0.153; 95% CI, –0.005 to 0.31).

Results differed between sexes. Higher cumulative sedentary time was associated with lower stroke volume index in girls (beta = –0.257; 95% CI, –0.496 to –0.018). However, the association was not present in boys (beta = 0.178; 95% CI, –0.038 to 0.394; P for interaction = .009)

“As we found that high levels of sedentary time and low levels of physical activity can lead to negative cardiac changes at early ages, clinicians should educate youth and their families about the detrimental effects of a sedentary lifestyle,” Haapala said. “Current physical activity guidelines state that children and adolescents should engage in vigorous-intensity physical activities at least 3 days a week. Our findings indicate that it may be a good investment for heart health to incorporate vigorous-intensity physical activity more often than the minimum recommended amount.”