Whether you can’t start the day without your morning run or you prefer to squeeze in your sweat sessions at the gym after a stressful workday, it’s a given that exercising at any point in the day is always better than being a couch potato. But does it really make a difference whether you work out in the morning or the evening? Turns out, it might, depending on your goals.MORE: Time-Crunched? Try These Quickie WorkoutsA recent study at Appalachian State University found that morning workouts are best if you want a better night’s sleep (and who doesn’t want that?). The researchers tracked the sleep patterns of people ages 40 to 60 who walked on a treadmill for 30 minutes, three times a week. Participants worked out at three different times: 7 a.m., 1 p.m. or 7 p.m. Turns out, those who hit the treadmill at 7 a.m. slept longer and had deeper sleep cycles than those who exercised at other points in the day. In fact, the morning crowd spent up to 75 percent more time in the reparative “deep sleep” stage at night.As a bonus, early birds also experienced a 10 percent reduction in blood pressure during the day and a 25 percent dip at night.The sleep changes that occur with morning exercise can alter our bodies mentally and physically, according to Scott Collier, Ph.D., the lead author of the study and an assistant professor in the department of health, leisure and exercise science at Appalachian State University.“The better you sleep, the better it is for your body,” explains Dr. Collier. “It increases your cardio health, decreases stress and anxiety, helps you maintain your weight and lowers your blood pressure. Plus, the more time spent in deep sleep, the more time your body has to repair itself.”COLUMN: Five Ways Sleep Keeps You Young Adds Collier: “If we can find the best time to exercise and get good sleep, we can we prevent the likelihood of people going from a pre-hypertension to hypertension state.”While morning exercisers can reap these rewards, along with a greater likelihood of sticking to their workouts, afternoon exercise comes with its own physical and psychological benefits, too.One small study found that afternoon exercise boosts workout performance. Researchers analyzed a group of cyclists who worked out at 6 a.m. or 6 p.m. and found that the evening exercises had higher power outputs. They theorized that the more complex the movements required to perform the exercise are, the more that the time of day can impact the performance. In other words, you may perform better in the afternoon if you’re swimming, running or biking versus something simple like walking.We may even be less prone to injury if we hit the gym or the pavement later in the day. That’s because our core body temperatures are higher at that time, making our muscles and joints more adaptable to exercise. But rolling out of bed for a workout doesn’t mean you’re doomed for injury, notes Felicia Stoler, an exercise physiologist and author of “Living Skinny in Fat Genes: The Healthy Way to Lose Weight and Feel Great.”“Morning exercisers will only get injuries if they don’t do something to warm up first,” says Stoler. But that doesn’t mean stretching, which Stoler says can lead to injuries when your muscles aren’t warmed up. Instead, she suggests opting for a brisk walk, light jog or jumping jacks.MORE: The Best Workouts for Your Body ShapeWhen it comes to weight loss, it’s a toss-up between mornings and evenings. In a study of post-menopausal women, participants were split into two groups. One group walked in the morning, while the other walked in the evening. At the end of the study, evening strollers did better overall with weight loss, losing more fat mass than morning walkers.On the flip side, research shows that exercising in a fasted state—which is usually only possible before breakfast—is better for weight loss because our bodies burn a greater percentage of fat for fuel during exercise, instead of relying on carbohydrates from food.Bottom line: Don’t sweat the time of day too much—just break a sweat whenever you can. “When it comes to weight loss, the key is to exercise whenever you can get it done,” advises Stoler. “It’s not always realistic to say you should exercise at a certain time. Exercise is beneficial regardless of the time of day you do it. That’s really what it boils down to.”QUIZ: How Physically Active Are You?