Brief intervals of exercise during otherwise sedentary periods may offset the lack of more sustained exercise and could protect children against diabetes, cardiovascular disease and cancer, according to a study by the US National Institutes of Health. The study involved 28 healthy children of normal weight who were randomly assigned to one of two groups. Children in the first group remained seated for three hours and either watched television, read, or engaged in other sedentary activities. Children in the second group alternated sitting with three minutes of moderate-intensity walking on a treadmill every 30 minutes for the three-hour period. Between seven and 30 days later, each child was tested again but switched groups. For each session, the children took an oral glucose tolerance test. On the days they walked, the children had blood glucose levels that were, on average, 7 per cent lower than on the sedentary day. Their insulin levels were 32 per cent lower.

Older adults who regularly engage in moderate to vigorous physical activity have more variable brain activity at rest than those who don't, and this is associated with better cognitive performance, according to a new University of Illinois study. One hundred adults aged between 60 and 80 were given accelerometers to measure their physical activity over a week. The researchers also used functional MRI to observe how blood oxygen levels changed in the brain over time, reflecting each participant's brain activity at rest. And they evaluated the microscopic integrity of each person's white-matter fibres, which carry nerve impulses and interconnect the brain. More active adults had higher brain variability and also performed better on complex cognitive tasks, especially on intelligence tasks and memory. They also had better white matter structure than their less-active peers.