Now, the researchers drew anonymized records for 48,440 adult men and women who used the Kaiser health care system, had their exercise habits checked at least three times in recent years and, in 2020, had been diagnosed with Covid-19. The researchers grouped the men and women by workout routines, with the least active group exercising for 10 minutes or less most weeks; the most active for at least 150 minutes a week; and the somewhat-active group occupying the territory in between. The researchers gathered data, too, about each person’s known risk factors for severe Covid, including their age, smoking habits, weight, and any history of cancer, diabetes, organ transplants, kidney problems and other serious, underlying conditions. Then the researchers crosschecked numbers, with arresting results. People in the least-active group, who almost never exercised, wound up hospitalized because of Covid at twice the rate of people in the most-active group, and were subsequently about two-and-a-half times more likely to die. Even compared to people in the somewhat-active group, they were hospitalized about 20 percent more often and were about 30 percent more likely to die.