Forced mild physical training improves blood volume in the motor and hippocampal cortex of old mice.

Objectives: To assess the effect of mild forced physical training on cerebral blood volume (CBV) and other brain parameters in old mice. Setting: Treadmill in the animal house. Participants: Thirty old (>25 mo) male mice were randomly assigned to one of three groups, exercise (E), exercise plus testosterone (T) (ET), and rest (C). Intervention: Mild physical training on treadmill (30 min a day at belt speed = 8 m/min, five days a week) with or without one weekly injection of testosterone. Measurements: CBV, quantitative transverse relaxation time (T2) maps, and cortical thickness were measured by magnetic resonance imaging. Results: A significant increase of CBV was found in the motor and hippocampal cortex of E and ET mice; cortical thickness was not affected. T2 maps analysis suggested that water distribution did not change. T administration did not add to the effect of physical training. Conclusion: This work provides first quantitative evidence that exercise initiated at old age is able to improve the hemodynamic status of the brain cortex in key regions for movement and cognition without inducing edema.