Even daily exercise may not prevent the effects of sitting for two hours

Regular exercise may improve fitness without cancelling out what happens to the body during a long, uninterrupted period of sitting. Researchers at Dalhousie University found that healthy young adults still experienced impaired function in a leg artery after sitting for about two hours.

The controlled study involved 21 participants. Eleven completed a 12-week high-intensity interval training program, while 10 continued their usual daily activities. Researchers used ultrasound to examine the popliteal artery behind the knee and measured how well it dilated before and after prolonged sitting.

The exercise group clearly improved its aerobic fitness and cardiorespiratory endurance. But after the participants sat continuously for about two hours, ultrasound still showed a marked decline in the artery’s dilation response. The temporary deterioration did not disappear because the participants had undergone intensive training.

The finding does not mean exercise is ineffective. Instead, the researchers said, better overall fitness and avoiding uninterrupted sitting address separate health indicators. Sitting at a desk for long periods without getting up can still affect local blood circulation, even among people who exercise regularly.

The study appeared in Applied Physiology, Nutrition, and Metabolism. Because the sample was small and consisted entirely of young people, the researchers said further studies are needed. They nevertheless advised people to stand up and move regularly during long periods of sitting.