The study measured the health (and leg strength) of 150 pairs of twin sisters from 43 to 73 years of age over the ten year period. Each sister performed leg extensions on modified equipment that measured their speed and power during the exercise. Then the participants performed computerized tasks to test their memory and mental processing skills.

Researchers discovered that the stronger twin, as demonstrated by leg power, sustained their cognitive abilities and suffered fewer brain changes or decline related to aging over the ten year period.

Dr. Claire Steves who led the King’s College project said: "When it came to cognitive ageing, leg strength was the strongest factor that had an impact in our study. We think leg strength is a marker of the kind of physical activity that is good for your brain."

In a recent BBC interview, Dr. Simon Ridley of Alzheimer's Research UK said: "We know that keeping active generally can help reduce dementia risk, and it's important to take into account strength training as well as aerobic exercise."

There is growing evidence that physical activity and exercise could be as beneficial to your brain’s health as well as your body’s. In a recent article published in the medical journal Gerontology, clinicians have identified chemicals in the body released by physical exercise that may boost elderly brain function and cognition.

More recent findings published in Psychology Today suggest that physical activity can improve cognitive function throughout your entire lifespan. A study conducted at the University of Minnesota showed that participants who began aerobic activities like running and cycling as young adults (age 25) preserved their memory skills and cognitive skills well into middle age. This “mental fitness” continued well beyond the actual duration of the physical activity.

A similar study conducted at the University of Eastern Finland measured memory and cognitive skills of physically active middle aged participants 43 to 55 and discovered that exercise during middle age prevents, or at the very least, delays the onset of mental decline or dementia.

There is growing evidence of a direct link between physical activity and cognitive function and ability. Moderate regular exercise conducted as little as twice weekly releases hormones and neurotransmitters that stimulate neurogenesis, the growth and repair of neurons and brain cells - regardless of your age.