Researchers from The Jackson Laboratory (JAX) and the University of Pennsylvania have identified a specific group of neurons in the hypothalamus that play a key role in endurance gains after exercise. Their study, published in Neuron, found that these neurons become highly active following physical activity and are necessary for improvements in endurance.
The research team focused on mice, monitoring the activity of hypothalamic cells during and after running sessions. They discovered that a cluster of neurons expressing steroidogenic factor-1 (SF1) was particularly active for about an hour after exercise ended.
"The fact that these neurons are most active post-run was quite intriguing," said Samuel S. Bloss of JAX. "It suggested that they play a role in signaling the body to start the recovery process."
Over several weeks of training, the number and strength of connections between SF1 neurons increased among exercising mice compared to those that did not exercise. Mice with more active SF1 neurons also developed more neural connections related to endurance.
To determine whether these neurons were essential for endurance gains, researchers used optogenetics to temporarily silence SF1 neuron activity for 15 minutes after each training session. Mice subjected to this intervention failed to improve their endurance despite continuing with rigorous daily exercise routines for three weeks. Additionally, these mice did not show typical muscle gene expression changes associated with endurance adaptation.
Bloss explained, "If you give a normal mouse access to a running wheel, they will run kilometers at a time. When we silence these neurons, they effectively don't run at all. They hop on briefly but can't sustain it."
In another experiment, artificially stimulating SF1 neurons after treadmill workouts led mice to outperform controls in both distance and speed by the end of their training period.
These results suggest that long-term benefits from exercise are coordinated by brain activity rather than solely by muscle adaptation. The findings may open new avenues for enhancing or replicating some effects of physical activity through targeting specific brain circuits.
"There's the very real possibility that we can eventually take advantage of this circuit to boost the effects of moderate exercise," Bloss said. "If we can mimic or enhance exercise-like patterns in the brain, that could be particularly valuable for older adults or people with mobility limitations who can't engage in intensive physical activity but could still benefit from exercise's protective effects on the brain and body."
Lauren Lepeak of JAX is also listed as an author on the study.
