2 . A small study out of Skidmore College examined the advantages of morning vs, evening exercise for both women and men. Paul, professor for health at Skidmore, led the study.

“We had the groups divided into evening and morning groups,” he says. “We found women and men answered differently to different types of exercise depending on the time of the day, which surprised us.”

The study showed that for women who want to lower blood pressure (血压), the risk of heart disease or reduce fat, morning exercise works best. Those women hoping for upper body muscle (肌肉) gains or mood (心情) improvement should consider evening exercise. For the men, the findings were somewhat different: Evening exercise lowers blood pressure, the risk of heart disease, and feelings of tiredness. But similar to women, they burn more fat with morning exercise.

“For many people, the best time to exercise will depend on their chronotype,” says Heisz, author of Move the Body, Heal the Mind.

“Chronotype is your body’s natural habit to sleep at a certain time—it’s what decides whether you’re a night owl or an early bird. For the 25% of the population that considers themselves a night owl, getting both enough sleep and enough exercise can be difficult,” adds Heisz.

He continues, “Sleep—which provides your body the necessary time to recover (恢复) and make gains from exercise—should always be the first choice. When it comes to exercise, regardless of research on the advantages of certain exercises at particular times of the day, your results will not be good if it doesn’t allow enough time for sleep.”

3 . As we age, even if we’re healthy, the heart just isn’t as efficient in processing oxygen as it used to be. In most people the first signs show up in their 50s or early 60s. And among people who don’t exercise, the changes can start even sooner.

“Think of a rubber band. In the beginning, it is flexible, but put it in a drawer for 20 years and it will become dry and easily broken,” says Dr. Ben Levine, a heart specialist at the University of Texas. That’s what happens to the heart. Fortunately for those in midlife, Levine is finding that even if you haven’t been an enthusiastic exerciser, getting in shape now may help improve your aging heart.

Levine and his research team selected volunteers aged between 45 and 64 who did not exercise much but were otherwise healthy. Participants were randomly divided into two groups. The first group participated in a program of nonaerobic (无氧) exercise—balance training and weight training—three times a week. The second group did high-intensity aerobic exercise under the guidance of a trainer for four or more days a week. After two years, the second group saw remarkable improvements in heart health.

“We took these 50-year-old hearts and turned the clock back to 30-or 35-year-old hearts,” says Levine. “And the reason they got so much stronger and fitter was that their hearts could now fill a lot better and pump (泵送) a lot more blood during exercise.” But the hearts of those who participated in less intense exercise didn’t change, he says.

“The sweet spot in life to start exercising, if you haven’t already, is in late middle age when the heart still has flexibility,” Levine says. “We put healthy 70-year-olds through a yearlong exercise training program, and nothing happened to them at all.”

Dr. Nieca Goldberg, a spokeswoman for the American Heart Association, says Levine’s findings are a great start. But the study was small and needs to be repeated with far larger groups of people to determine exactly which aspects of an exercise routine make the biggest difference.