Activity levels among children fell below national guidelines after Covid-19 restrictions eased, a study finds.
A university of Bristol study found by the end of 2021, less than a third were meeting the recommended guidelines of 60 minutes of physical activity daily.
The findings showed children in England aged between 10 and 11 were doing eight minutes less activity than before 2021.
Researchers said it "highlights a greater need" to work with families, and schools to get children active.
Nearly 400 children and their parents from 23 schools in Bristol were recruited for the study.
They wore accelerometers to measure the intensity of physical activity and answered questionnaires about their lifestyles.
The information was compared with data from 1,296 children and their parents who were recruited from 50 schools in the same area prior to lockdown.
University of Bristol Professor Russ Jago said the results were "surprising".
"Changes in physical activity patterns did not revert to previous levels once freedoms had been restored," he said.
"These findings highlight a greater need to work with children, families, schools, and communities to maximise the opportunities for children to be physically active as we emerge from the Covid-19 pandemic."
Researchers said children were less active at the weekend than during the week, taking part in 46 minutes of moderate to vigorous physical activity on Saturdays and Sundays.
The study also revealed a marked increase in sedentary time, with children spending 25 minutes longer being sedentary per day than previously during the week.
University of Bristol statistician Dr Ruth Salway said: "The key strength of this study was we used data collected before and after the pandemic, using the same methods and in the same schools.
"The data clearly demonstrates children's physical activity had deteriorated once the restrictions were lifted."