Noting that there is no clear guidance on the intensity and duration of PA that adolescents require to maximize CRF, Samuel Joseph Burden, from the John Radcliffe Hospital in Oxford, England, and colleagues examined the strength of association between each PA intensity and CRF. PA was assessed by wrist-worn accelerometers, and CRF was assessed with 20-m shuttle runs among 339 adolescents aged 13 to 14 years.
The researchers found that up to about 20 minutes of daily VPA, greater VPA was associated with better CRF, at which point the association plateaued. In partial models, there were no associations for moderate and light PA and sedentary time with CRF. Median CRF was seen for adolescents performing 14 minutes of daily VPA. Participants in the upper versus the lower quartile of VPA had 1.03 z-scores higher CRF (95 percent confidence interval, 0.75 to 1.30).
“This modest duration and more specific intensity of PA may provide a better underpinning for future guidelines that currently recommend a longer duration of less specific activity (moderate to vigorous physical activity) each day,” the authors write. “Further work should aim to test whether interventions based on this new target offer significant improvements in adolescent cardiometabolic health.”