Whether you like to break a sweat during a 6 a.m. workout or burn off steam with a 6 p.m. visit to the gym, exercising regularly at any point of the day helps keep you healthy and fit. Everyone has their own theories and preferences regarding the “best” time of the day to train, but does it really make a difference whether you work out in the morning or the evening?

It all comes down to what your fitness goals are. Are you working out for a good night’s sleep? Maybe you’re trying to lose weight or increase muscle mass. The best time of the day for you to work out depends on your answers to these questions. If you know what your goals are, look below for the best times.

Weight Loss: Morning/Evening Workout

When it comes to shedding the pounds, it’s a tie between morning and evening workouts. A 2010 study published in The Journal of Sports Medicine and Physical Fitness found evening strolls led more post-menopausal women to lose weight and fat mass than women who went on morning strolls. Evening strolls were also found to change women’s dietary habits; they ate more in the mornings. Eating breakfast in the morning can reduce the likelihood of obesity, stabilize blood sugar levels, and even suppress appetite later on in the day.

Conversely, a 2010 study published in the Journal of Physiology found exercising before breakfast helps dieters achieve better weight loss results because the body burns a greater percentage of fat for energy during exercise rather than depending on carbs from food. This study was the first to show that fasted training is more beneficial than fed training to energize the body and improve glucose tolerance in a fat-rich diet. Morning workouts prime the body for an all-day fat burn.

To lose weight, it all comes down to when you’re the most available to commit to a regular workout routine.

Boost Muscle Strength: Evening Workout

A rule-of-thumb is that muscle strength tends to be at its lowest in the morning, and then increases gradually until it reaches peak levels in the early evening. A 1998 study published in the journal Medicine and Science in Sports Exercise observed how time of day affected muscular performance in a cohort of untrained men in their early 20s. The men performed a series of strength tests at different times, including 8 a.m., 12 p.m., 4 p.m., and 8 p.m. Muscle strength was greatest in the evening, but only during exercises that involved faster movements. In other words, maximal muscle strength varies with the time of day and is contingent on the speed of the workout.

Boost Muscle Size: Evening Workout

One question many fitness gurus have is whether an evening or morning workout will help them build more muscle and lose fat faster. A 2009 study published in the Journal of Strength and Conditioning Research found there are greater gains in muscle size when trainers work out during the evening hours. A group of young men were trained between 5 p.m. and 7 p.m. for the first 10 weeks of the study. Then, for the next 10 weeks, the men were divided into two groups: a morning group (7 a.m. to 9 a.m.) and an afternoon group (5 p.m. to 7 p.m.). The researchers found all men gained size and strength, but the afternoon group gained an average of 3.5 percent more, compared to 2.7 percent more in the morning group.

These findings are best explained by a phenomenon known as temporal specificity, in which muscular strength adapts to be at its strongest at the time of the day the training occurred. If you’re consistently training in the evening, it will improve your muscle strength in the evening.

Boost Work Performance: Afternoon Workout

To boost your work performance, especially if you’re in an afternoon slump, work out in the afternoon. A 2009 study published in the journal Chronobiology International found evening exercises delivered more of an energy boost to cyclists who worked out at 6 p.m. rather than 6 a.m. The afternoon is better for high-intensity exercises, such as swimming, running, or biking, rather than walking. In part, this is because core body temperature is higher in the afternoon, which means muscles and joints are readier for exercise — there’s also a lower chance of getting injured at this time.

Improve Sleep and Reduce Stress: Morning Workout

Setting up your alarm clock for early morning workouts can actually give you a good night’s sleep and reduce your stress levels. A 2011 study published in the Journal of Strength and Conditioning Research tracked blood pressure levels and sleep patterns in participants between the ages of 40 and 60. Each participant exercised moderately by walking on a treadmill at 7 a.m., 1 p.m., and 7 p.m. for 30 minutes three times a week. The researchers found that all of the participants who exercised at 7 a.m. experienced an overall 10 percent reduction in blood pressure and a 25 percent drop in blood pressure at night.

Morning workouts also helped the volunteers sleep longer and go through deeper sleep cycles when compared to exercising at other times of the day. The morning group spent up to 75 percent more time in the deep sleep stage at night. These early birds not only increased their cardiovascular health, but also decreased their stress and anxiety thanks to a good night’s sleep. Basically, the more deep sleep the body gets, the more time the body has to recuperate.

Regardless of the time of day you work out, consistency is key. In theory, this means it’s best to work out whenever you’re able to stick with it on a daily basis. The Centers for Disease Control and Prevention (CDC) suggests 150 minutes of moderate-intensity aerobic activity every week and muscle-strengthening activities on two or more days a week that include all the major muscle groups, such as legs, hips, back, abdomen, chest, shoulders, and arms. However, breaking it up into smaller chunks of time during the day, about 10 minutes, at a time is fine.