The researchers at the National Cheng Kung University Medical College suggest exercise promotes the production and maturation of new stem cells by helping restore a brain chemical known as neurotrophic factor and its receptor, TrkB.

When fewer new stem or progenitor cells are produced in the hippocampus -- a part of the brain which plays an important role in memory and learning -- impairment of the learning and memory functions result, the researchers said.

The researchers found exercising middle-aged mice improved their production of new nerve cells by about 200 percent over that produced in sedentary mice. Exercise also significantly enhanced stem cell production and maturation in the young mice, the study said.

The effect of exercise in young mice was stronger than the effect in the older mice.

The study was published in the Journal of Applied Physiology.