Regular exercise causes long-lasting elevations in the brains basal glycogen levels though the buildup of repeated supercompensation.
Exercise supercharges your brain. According to the latest findings from a Japanese study, exercise results in sustained elevated glycogen levels (Brain glycogen super compensation following exhaustive exercise, 2012, Takashi Matsui, et al.). Glycogen levels have been shown to be elevated in skeletal muscle following exercise, but this is the first study to report of the phenomenon in the brain.
Exercise's effect on glycogen levels in the skeletal muscle have been known for some time. During exercise, glycogen stores are depleted, but the body returns to an elevated level of glycogen in a process called supercompensation. Supercompensation was first reported in the skeletal muscle in the 1960s. In the 1980s researchers found that skeletal muscle responds to exercise training by maintaining higher basal levels of glycogen. This adaptation to exercise training lengthens the amount of time the muscle can work before exhaustion.
To study the effects of exercise on glycogen levels in the brain, researchers trained mice for 60 minutes a day, 5 days a week for 3 weeks. At the end of the study glycogen levels were observed in the liver, skeletal muscle and brain. During exhaustive exercise, glycogen levels in the brain dropped 50-60%. Glycogen levels in the liver and skeletal muscle dropped 80-90%. The brain was the first to recover from exercise-induced glycogen depletion by peaking at 6 hours after exercise. This supports the "Selfish Brain Theory": the brain wins during competition for energy resources within the body. Following supercompensation, the brain returned to pre-exercise glycogen levels about 48 hours after exercise. The skeletal muscle took 48 hours to return to pre-exercise glycogen levels following exercise. A supercompensation peak 24 hours after exercise was recorded in the skeletal muscle. The liver did not show supercompensation and took 48 hours to recover pre-exercsise glycogen levels. These results can be seen in the figure below.
More insight was achieved by comparing glycogen levels in the brain between exercise-trained mice and a sedentary control. Glycogen levels in the brain were found to be significantly higher in the exercise-trained mice. The exercise-trained mice were killed 72 hours following the last bout of exercise and their brain tissue was evaluated. The cortex and hippocampus, but not the hypothalamus, brainstem or cerebellum, were found to have significantly higher levels of glycogen than the control. This suggests that supercompensation in the brain results in a long-lasting increase in glycogen levels. The differences in brain glycogen levels between exercise-trained and sedentary control mice can be seen in the figure below.
An interesting correlation was found between exercise-induced glycogen depression and the supercompensation that followed. The glycogen depression and supercompensation that followed were positively correlated; that is, a greater glycogen depression results in a stronger glycogen supercompensation in the brain.
Exercising daily causes the brain to have elevated levels of basal glycogen after just three weeks. What are some potential benefits? There are obvious benefits to endurance athletes. Low sugar levels in the brain are a major source of fatigue. Therefore, elevated glycogen levels would help alleviate onset of fatigue during endurance competition. In addition, increases in glycogen levels have been linked to an increase in cognitive. It has been reported on exercismed.org that students who exercise demonstrate better academic performance (See Lifestyle Impact on Academic Performance). Could the glycogen that supercharges their brain be the biological mechanism?
Exercise is the supercharger of brains.