According to a CNN article by By Sandee LaMotte of Tuesday, June 2, 2020, "Scientists believe exercise increases blood circulation to the brain, especially areas like the amygdala and hippocampus — which both have roles in controlling motivation, mood and response to stress. For one thing, it releases endorphins, the body's feel-good hormones."
It goes on to say that "high-intensity interval training ... increased stress and inflammation ... [and] could make an already stressed-out system more jittery, "especially in individuals who were not accustomed to exercise," said study author Jennifer Heisz in an article she wrote."
Further more the article states "Studies have found that tai chi and qi gong increase blood levels of endorphins, reduce levels of the stress hormone cortisol and improve immune function, a key benefit in the age of coronavirus. And brain scans of people using tai chi and qi gong find increased alpha, beta and theta brain wave activity, suggesting increased relaxation and attentiveness."