Is it better for our bodies to work out at certain times of the day? Scientists have known for some time that every tissue in our bodies contains a kind of biological clock that goes off in response to messages related to our daily exposure to light, food and sleep.
However, whether and how exercise timing might influence metabolic (新陈代谢的) health has been less clear, and the results of past experiments have not always agreed. A much-discussed 2019 study found that men with Type 2 diabetes (糖尿病) who completed a few minutes of high-intensity interval (间隔) sessions in the afternoon improved their blood-sugar control after two weeks. Patrick Schrauwen, a professor of nutrition and movement sciences read that 2019 study with interest. He had been studying exercise in people with Type 2 diabetes, but had not considered the possible role of timing. Now, seeing the varying impacts of the intense workouts, he wondered if the timing of workouts might similarly affect how the workouts changed people's metabolisms.
Incidentally, he and his colleagues had a ready-made source of data in their own prior experiment. Several years earlier, they had asked adult men at high risk for Type 2 diabetes to ride stationary bicycles at the lab three times a week for 12 weeks, while the researchers tracked their metabolic health. They also had noted when the riders showed up for their workouts. The researchers pulled data for the 12 men who consistently had worked out between 8 and 10 a.m. and compared them with another 20 who always exercised between 3 and 6 p.m. They found that the benefits of afternoon workouts far outweighed those of morning exercise.
He says, "This study does suggest that afternoon exercise may be more beneficial for people with disturbed metabolisms than the same exercise done earlier. The particular and most effective exercise for each of us will line up with our daily routines and exercise tendencies because exercise is good for us at any time of day—but only if we choose to keep doing it."
