The researchers concluded that the mice do not show any improvement in endurance, regardless of the intensity of running on the device designated for this purpose, without the activity of nerve cells in the brain.
But when the researchers artificially activated the neurons after exercise, the animals gained greater endurance than usual, according to the study published in the journal Neuron.
“The idea that muscle remodeling requires the activation of these neurons in the brain is a big surprise,” study leader Eric Bloss said in a statement.
He added, “This really challenges traditional thinking” that the benefits of exercise come from muscles only.
By tracking brain activity in mice during and after running, the researchers found that a specific group of neurons, in the hypothalamus area of the brain (hypothalamus), that secrete a type of protein called “Steroidogenic Factor 1,” or “SF1,” became active for about an hour after the mice finished running.
As the mice continued to exercise over a period of weeks, more SF1-producing neurons became active after each exercise, and the connections between those specific neurons became stronger and larger in number, according to the researchers in the study.
The researchers also concluded that the animals that exercised had twice the number of connections between these neurons compared to the animals that did not exercise.
When the researchers “switched off” the activity of SF1-producing neurons for 15 minutes after each exercise session, the mice stopped improving their endurance and began to show worse performance on voluntary running tests.
“If you give a normal mouse a running wheel, it will run kilometers at a time,” Bloss said. “When we turn off these neurons, the mice don’t run at all. They jump briefly but can’t continue.”
When the researchers stimulated the neurons via SF1 for an hour after running, the mice showed improved endurance and reached higher speeds.
“There is a very real possibility that we may eventually be able to leverage this relationship to increase the effects of moderate exercise,” Bloss said. “If we can mimic or enhance exercise-like patterns in the brain, this could be particularly beneficial for older people or those with health problems that limit movement, who cannot engage in intense physical activity, but who could nonetheless benefit from the protective effects of exercise on the brain and body.”
