Doctors have long counseled older patients to stay in shape by walking every day. While stronger legs may not be the goal of a walking regime, a new study suggest that there may be a correlation between leg strength and healthy brains as people age.

The study published in the medical journal Gerontology suggests that leg power may be an indicator of whether older people are getting adequate exercise for brain health, according to the BBC. The study is the result of a decades-long research project by a team from the Kings College of London that followed more than 300 participants.

Interestingly, the study looked at twin sisters, so the data is especially intriguing to medical researchers, who try to evaluate the influences of genetics versus the environment. Looking at twins can help clarify these issues, since their genetic foundation is virtually identical.

More than 150 pairs of twin sisters participated in the study, and at the onset of the trial the sisters were between the ages of 43 and 73. At the start of the study, the researchers measured participants leg power using gyn equipment to quantify both the speed and extension of leg power.

Brain health was measured at the beginning and end of the study using memory and mental processing tests. The results showed that the twin who had stronger legs at the start of the study maintained their brain health better through the ten-year period, with fewer of the brain changes that are associated with aging. The findings remained even after accounting for known lifestyle factors, such as overall heart health, and risk factors for dementia.

Still, it is challenging to evaluate the contribution of leg strength versus other lifestyle factors that could make an impact on brain health. Also, the researchers noted that they did not assess the participants for dementia.