It has already been recognised that age affects how physical fitness reflects mental fitness in people, especially those who are getting older. However, a new study shows that older fitter men can still perform better mentally as exercise could help them use parts of the brain commonly used by younger people.

The new study explains how older adults experience the phenomenon called hemispheric asymmetry reduction in older adults (HAROLD). This phenomenon reflects the reorganisation of the brain to respond on the decreasing brain capacity and efficiency because of age-related structural and physiological decline.

HAROLD occurs when an aging adult tend to use both sides of the prefrontal cortex (PFC) in doing mental tasks instead of just one due to brain reorganisation. Older adults use the right and left PFC to perform tasks that involve temporary storage and manipulation of memory, long-term memories and inhibitory control.

Earlier studies have already found that young adults commonly use the left side of the PFC. In the current study, those physically fit, older adults have also been found to use the left side of the PFC, which indicates that they can perform better mentally with this youth-like, task-related side of the brain.

The study, published in the journal NeuroImage, shows the direct link between physical fitness, brain activity and brain function in a group of older Japanese men. The researchers first measured the aerobic fitness of 60 older men, ages 64 to 75, before a mental test.

As the participants were proven physically fit, they were asked to take a “colour-word matching Stroop test” to measure their brain function. The Stroop test involves showing the participants names of colours but being asked to name the colour of the letters which is different to what they can read.

The difference in the colour of the letters and the name of the colour it shows, like the word “blue” is printed in colour “red” for example, requires the brain to take longer time to react. The reaction time has been used by the researchers to measure the participants’ brain function.

The researchers also measured the activity in the PFC region of the brain of the participants during the test through the neuroimaging technique known as functional near infrared spectroscopy (fNIRS).

The results show that older adults tend to have both sides of their PFC active during the Stroop test, without having a difference between right and left regions. The result proves the HAROLD phenomenon occurs on older male adults.

The analysis of the test results shows that men who favour the left side of the PFC have faster reaction times. The researchers said that aerobic fitness was linked to shorter reaction times and higher left-PFC activity.

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