Cardiorespiratory fitness is a measure of the body’s ability to deliver oxygen to skeletal muscles during sustained physical activity. Findings from a new study suggest that higher cardiorespiratory fitness may increase the brain’s gray matter.

Gray matter contains the cell bodies, dendrites, and axon terminals of neurons in the brain. Loss of gray matter is associated with cognitive decline and memory loss – hallmarks of dementia. Physical inactivity promotes gray matter losses and is a major risk factor for dementia.

The new study involved more than 2,100 adults between the ages of 21 and 84 years living in Germany. The authors of the study assessed the participants' cardiorespiratory fitness based on peak oxygen uptake during exercise on a stationary bike. They also measured the participants' gray matter and total brain volume using magnetic resonance imaging (MRI).

The MRI analysis revealed that for a single standard deviation increase in peak oxygen uptake, gray matter volume increased by more than 5 cubic centimeters in regions associated with emotion, memory encoding, learning, and decision making. These findings suggest that physical activity that promotes cardiorespiratory fitness might be a means to prevent dementia associated with gray matter losses.

Sauna bathing is an exercise mimetic and promotes many of the cardiovascular benefits associated with exercise. Dr. Rhonda Patrick describes some of these effects in this podcast.

• Link to full study.