Older adults who have good cardiac fitness may experience more brain activity during learning and perform better in memory tasks, a new study has found.

In a study by Boston University in the US, older adults who scored high on cardiorespiratory fitness (CRF) tests performed better on memory tasks than those who had low CRF.

Further, the more fit older adults were, the more active their brain was during learning.

Difficulty remembering new information represents one of the most common complaints in ageing and decreased memory performance is one of the hallmark impairments in Alzheimer's disease.

Healthy young (18-31 years) and older adults (55-74 years) with a wide range of fitness levels walked and jogged on a treadmill while researchers assessed their cardiorespiratory fitness by measuring the ratio of inhaled and exhaled oxygen and carbon dioxide.

These participants also underwent MRI scans which collected images of their brain while they learned and remembered names that were associated with pictures of unfamiliar faces.

The researchers found that older adults, when compared to younger adults, had more difficulty learning and remembering the correct name that was associated with each face.

Age differences in brain activation were observed during the learning of the face-name pairs, with older adults showing decreased brain activation in some regions and increased brain activation in others.

However, the degree to which older adults demonstrated these age-related changes in memory performance and brain activity largely depended on their fitness level.

In particular, high fit older adults showed better memory performance and increased brain activity patterns compared to their low fit peers.

The increased brain activation in the high fit older adults was observed in brain regions that show typical age-related decline, suggesting fitness may contribute to brain maintenance.

Higher fit older adults also had greater activation than young adults in some brain regions, suggesting that fitness may also serve a compensatory role in age-related memory and brain decline.

According to the researchers this study highlights that CRF is not only important for physical health, but is also associated with brain function and memory performance.

"Importantly, CRF is a modifiable health factor that can be improved through regular engagement in moderate to vigorous sustained physical activity such as walking, jogging, swimming, or dancing," said Scott Hayes, assistant professor at Boston University School of Medicine.

"Therefore, starting an exercise programme, regardless of one's age, can not only contribute to the more obvious physical health factors, but may also contribute to memory performance and brain function," said Hayes.

The study was published in the journal Cortex.