Along with a healthy diet, quality sleep and regular exercise are generally cited as the vital building blocks of a healthy lifestyle. Unfortunately, there is a considerable amount of confusion around what exactly is the best time to work out — specifically in regard to your sleep quality. How does exercise affect sleep? Do certain types of exercise impact your sleep in different ways?

Understand Your Rhythms

In order to fully understand how to time your workouts, the first thing to consider is the natural changes that your body cycles through on a daily basis. When you first wake up, your core temperature is relatively low. Levels of melatonin — a hormone that causes you to feel tired — are still pretty high, however.

Throughout the day, though, your temperature steadily increases — reaching a peak around 2 to 4 p.m. That rise in temperature causes your melatonin levels to decrease. As daylight decreases, however, your temperature drops and melatonin increases.

This cycle and balance has a huge impact on your sleep. How does exercise fit in?

Impact of Exercise

As mentioned, this cycle — called the circadian rhythm — is deeply connected with the amount of sunlight that you are exposed to. According to the National Sleep Foundation and the American Council on Fitness, individuals who exercise outdoors around 7 a.m. sleep longer and more deeply than people who work out later in the day. In addition, this morning dose of sun and activity allows people to spend an average of 75 percent more time in the reparative phases of sleep.

So, does this mean that the morning is the best time to work out? Not necessarily. Since your core temperature is highest in the afternoon, moving your workouts to fit within that window can increase your performance and give you a boost of energy during a time when most people tend to lose energy. In addition, that afternoon gym session will typically keep your body temperature elevated for the next four to five hours — at which point your temperature will decrease and your melatonin will increase. As a result, your body will naturally start preparing for sleep.

But that's not everything to consider. Many workout styles are specifically designed to increase your heart rate, stimulate the release of energizing endorphins and increase your core temperature. All of these changes will wake you up and could make it more difficult for you to fall asleep. Because of this, many experts recommend avoiding any type of intense exercise two or three hours before going to sleep. It is very important to note, however, that not everyone has difficulty falling asleep after exercising.

Putting It Together

Clearly, the question of "How does exercise affect sleep?" has no easy answer. Over the long-term, your workouts can absolutely help you sleep longer and more deeply. However, an intense workout too late in the evening may have the opposite effect for some people.

Simply put, then, the best time to work out is the time that you can stick to. Remember, exercise is all about regularity. Experiment with different times of day and see how you respond — both during the day and at night.