A healthy body does indeed make a sound mind— a new study confirms that people who practice sports regularly have a better sustained attention span than those in poor physical health. The benefits of physical fitness also translate to higher functioning of the autonomic nervous system (ANS), which promotes general brain functions.

In a study published today in the journal PLOS One, researchers from the University of Granada in Spain put 28 young Spanish men through a series of computerized attention tasks in order to see how fitness level related to their performance.

Half of the participants were college students who had low physical fitness according to the standards of the American College of Sports Medicine, and the other half were either athletes at the same university or members of the Andalucía Cycling Team's under-23 division.

The attention tasks tested sustained attention, the ability to respond to randomly timed interruptions of a monotonous task; temporal attention, the ability to judge when particular timed events will occur; and time perception, the ability to judge differences in the duration of two different stimuli.

The researchers also measured their heart rate variability (HRV), which indicates how efficiently the autonomic nervous system alters the heart rate in response to physical demands like exercise. Previous research has suggested that increased physical fitness can improve vagal tone, a biological process in the brainstem that promotes efficient autonomic nervous system functioning and greater HRV. While exercise improves HRV, high anxiety levels and cognitive stress can decrease it.

Participants wore electrodes measuring HRV on their chests throughout the attention tasks, at rest, and during a stationary cycling session that tested their fitness level.

The results showed that the physically fit group performed much better on the sustained attention tasks, though there were no differences in the other two types of attention. The athletes also showed more rapid reaction times than their sedentary counterparts.

The attention tasks did seem to affect heart rate variability in different ways, indicating possible differences in how the autonomic nervous system responds to distinct types of attention. Time perception tasks reduced HRV more than the other tasks, which the researchers believe suggests that the autonomic nervous system is more stressed by perceptual demands than by attentional demands.

The sedentary participants also showed a general decrease in HRV as more time passed, suggesting that their lower fitness made them less able to deal with cognitive stress over long time periods.

The results suggest that the cyclists' strong physical fitness "appeared to be associated with the processes implicated by sustained attention," said lead researcher Antonio Luque Casado in a statement.

His findings add to previous evidence that exercise can boost brain function. Other studies found that practicing sports can prevent cell death in the brain, and promote the growth of new neurons in key brain areas related to memory, movement, and higher-order thoughts.

The New York Times also announced separate studies about the brain-boosting benefits of fitness today, including one published in The Journal of Aging Research, indicating that different types of exercise can improve distinct types of memory even in old age.