New York, July 31 (IANS): Ever wondered why you get more physically exhausted when certain issue keeps you worried? This could be because brain work accelerates the development of physical fatigue, says a new study by Indian-origin researchers.

The study showed that when we attempt mental tasks and physical tasks at the same time, we activate specific areas, called prefrontal cortex (PFC), in our brain. This can cause our bodies to become fatigued much sooner than if we were solely participating in a physical task.

Typically, endurance and fatigue have been examined solely from a physical perspective, focused primarily on the body and muscles used to complete a specific task.

However, the brain is just like any other biological tissue, it can be overused and can suffer from fatigue.

"Not a lot of people see the value in looking at both the brain and the body together," said Ranjana Mehta, assistant professor at the Texas A&M Health Science Center School of Public Health in the US.

The researchers found that there were lower blood oxygen levels in the PFC following combined physical and mental fatigue compared to that of just physical fatigue conditions.

Through simultaneous examination of the brain and muscle function it is apparent that when participating in highly cognitive tasks, brain resources are divided which may accelerate the development of physical fatigue, the study said.

Co-author of the study is Raja Parasuraman, professor of psychology at George Mason University in Virginia.

The findings were detailed online in Human Factors: The Journal of the Human Factors and Ergonomics Society.