Could running in high temperatures further boost exercise-induced neurogenesis? Though probably unrelated, I've always felt that workouts in warm weather are more satisfying.
Aerobic exercise is well-documented to increase neurogenesis in animals.
The brain was originally thought to have a fixed number of neurons by adulthood. Neuroscience underwent a paradigm shift with the discovery that new neurons are born (and functionally integrated into neural circuitry) well into adulthood.
Neurogenesis has since been implicated in depression and a number of other disorders. Hundreds of peer-reviewed articles have been published in the last two decades about the role of neurogenesis in the mechanism of action of antidepressants.
Neurogenesis and Extreme Temperatures
Researchers asked whether exercise-induced neurogenesis is affected by ambient temperature.
Specifically, they hypothesized the following:
Spoiler: they were wrong (partially)!
The brain is sensitive to both hot and cold temperatures and thus the body goes to a great deal of trouble to ensure that it maintains homeostasis.
The authors assumed that since heat dissipation is taxing and the brain must be kept cool, that running in the cold would boost neurogenesis and running in the heat would suppress neurogenesis.
To the authors surprise, aerobic exercise at both low and high-temperatures increased neurogenesis compared with aerobic exercise at normal temperatures.
Though the underlying mechanism remains unknown, it may be that temperature extremes plus exercise are mild stressors that result in beneficial adaptations in the brain. I'm thinking specifically of eustress.
Mild stressors improve performance (e.g., being moderately nervous before an exam), but chronic unpredictable stress impairs performance.
Moderate oxidative stress has been known to result in improved antioxidant defense, whereas severe oxidative stress overwhelms protective mechanisms, resulting in oxidative damage.
Maynard ME, Chung C, Comer A, et al. Ambient Temperature Influences the Neural Benefits of Exercise. Behav Brain Res. 2015;