Is Working Out Before Bed Good or Bad for You?

After a long day at work, nothing soothes the soul quite like coming home to a warm bath, a good book, relaxing tunes and — a 45-minute total-body workout?

It's surprisingly true: Physical activity — even in the evenings — has many proven benefits, including better sleep. However, that hasn't quashed the belief that working out at night actually has the opposite effect of delaying bedtimes and worsening sleep quality.

Is there any truth to the matter, or is this nothing more than a battle of the early birds versus night owls in their never-ending pursuit to prove the other less-than?

"There is strong evidence that demonstrates regular physical activity actually improves sleep outcomes, including sleep quality, deep sleep, and feelings of daytime tiredness," says Dr. Aarthi Ram, a Houston Methodist neurologist who specializes in sleep medicine. "However, most American adults don't actually get enough recommended exercise to begin with, and roughly a third don't get enough quality sleep."

"Could a late-night workout lead to poor sleep?" she asks. "It's definitely possible, but it's going to depend on the person: their body, their behaviors and how they feel in response to changes in those behaviors, such as exercising more, exercising earlier or trying to get more sleep."

So what does that mean for your exercise and sleep routines? Dr. Ram breaks down the relationship between physical activity and sleep and what factors you may want to consider beyond late-night workouts that can cause a poor night's rest.

Regular exercise can improve multiple aspects of sleep

"Studies have shown that adults who are more physically active take less time to fall asleep, get more deep sleep, spend more time in bed actually sleeping and require less frequent use of sleep-aid medications," says Dr. Ram.

It's all in relation to hormones, she says. Specifically, exercise releases a cocktail of feel-good hormones, including endorphins, the body's natural painkillers that help lower anxiety and stress; dopamine, the neurotransmitter responsible for pleasure and reward; and serotonin and norepinephrine, which help regulate mood and relaxation.

Physical activity can also decrease levels of cortisol and adrenaline — hormones responsible for increasing our blood pressure, heart rate and energy levels in response to stressful or dangerous situations.

(Related: How Much Melatonin Is Too Much?)

"Exercise also helps regulate the circadian rhythm, the body's natural sleep-wake cycle," says Dr. Ram. "When this 'clock' is off, you're likely to experience trouble falling or staying asleep, trouble waking up, daytime sleepiness, headaches, fatigue and even depression."

Many things can throw your circadian rhythm out of alignment, including jet lag, unhealthy sleep habits, alcohol use, caffeine use and sleep disorders like insomnia and obstructive sleep apnea (both of which exercise has been shown to improve). Depending on a few key factors, says Dr. Ram, nighttime exercise can join that list.

Duration, type and intensity of night workouts may matter

When you work out, your muscles generate heat and cause your body temperature to rise, which is why we sweat during workouts. It's our bodies' natural way of cooling off. Vigorous workouts, such as running and endurance training, tend to raise our heart rates and body temperatures more than light-to-moderate workouts, such as walking, mowing and gardening.

However, our body temperature, like our circadian rhythm, follows a 24-hour cycle that rises during the day and falls at night. It's thought that this nightly decrease is our body's way of winding itself down in preparation for sleep.

"The theory behind why late-night workouts may interfere with our natural sleep-wake cycle is that not only can they raise our core body temperature, but they can also increase our heart rate," says Dr. Ram. "Both are naturally meant to fall at night. While the evidence is mixed, some studies have shown that vigorous physical activity, due to its greater rise in body temperature and heart rate, may contribute to worse sleep quality and more time to fall asleep."

"However, other studies have suggested that late-night workouts, even vigorous ones, have either no effect on or are, in fact, beneficial to sleep," she adds. "It's clear more research is needed."

In the meantime, Dr. Ram says most people could benefit from more exercise rather than less — whether the exercise is light, moderate or vigorous.

"Doctors want people to exercise more," she says. "Whether you exercise at night, in the afternoon or in the morning, is up to you."

(Related: Why Am I So Tired?)

Are you getting enough exercise to experience the sleep benefits?

Adults need at least 150 minutes of moderate-intensity aerobic exercise and at least two days of strength training per week to maintain good physical health, according to the U.S. Department of Health and Human Services' physical activity guidelines. The guidelines' definition of good physical health also covers brain health, including sleep, anxiety, mood and cognition.

Moderate aerobic activity is anything that gets your heart beating faster, including:

• Walking fast
  
• Biking on level ground
  
• Swimming
  
• Mowing the lawn
  
• Doubles tennis
  

Alternatively, you can swap those 150 minutes of moderate-level activity for 75 minutes of vigorous aerobic activity, exercises that leave you breathing hard and fast. Or you can mix and match exercises to total up to the recommended amount. One minute of vigorous aerobics is roughly equal to two minutes of moderate activity.

Vigorous aerobic activity includes:

• High-intensity interval training (HIIT)
  
• Jogging or running
  
• Swimming laps
  
• Biking fast or on hills
  
• Singles tennis
  
• Basketball
  

An equally important part of fitness, muscle strengthening can help to improve bone density, blood pressure, weight maintenance and maintain lean muscle mass during weight loss.

Examples of strengthening activities include:

• Lifting weights
  
• Resistance band exercises
  
• Bodyweight workouts (like pushups, pullups and planks)
  
• Heavy gardening
  

Unfortunately, most adults don't meet these guidelines: Only 26 percent of men, 19 percent of women and 20 percent of adolescents get the recommended exercise to maintain good health, according to the Department of Health and Human Services.

"An inactive lifestyle can lead to poor sleep, which can make you feel too tired to exercise," says Dr. Ram. "They unfortunately compound each other and create a cycle that can be hard to break."

(Related: How to Start Exercising in 4 Easy Steps)

Are you getting enough sleep?

Most healthy adults need at least seven hours of sleep nightly. However, everyone's sleep needs are different. For instance, one person may feel rested after just seven hours, but another may need eight or nine, which is still within the normal range of recommended sleep. Children tend to need even more: Newborns can sleep up to 17 hours, toddlers 14 and teenagers up to 10.

(Related: How Much Sleep Do You Really Need?)

Keep in mind — those numbers are in hours of quality sleep. Some people with sleep disorders such as insomnia or sleep apnea may not get enough quality sleep, no matter how hard they try. Anything less than seven hours of sleep is generally considered not enough sleep.

"Lack of sleep, whether acute (meaning 'one bad night') or accumulated (meaning several nights of insufficient or poor quality sleep), results in measurable changes in your daily performance, alertness and behavior," says Dr. Ram. "You may take longer to respond to certain tasks, your critical thinking could be affected and your energy may be low enough to where you don't even feel like doing much, including working out."

"And while you can 'catch up' on sleep on the weekends, studies in adolescents have shown that catching up is not the same but rather inferior to a good night's rest," she says.

Ultimately, more than one-third of U.S. adults do not get enough sleep, according to the Centers for Disease Control and Prevention, which Dr. Ram says may be a contributing factor in skewing people's perception that their evening workout routines are the culprit of their tiredness and fatigue.

"If you've shifted your workouts earlier, are exercising more and yet still have difficulty sleeping, it may be time to see a sleep medicine specialist to further explore the cause, whether it's exercise-induced or something else like sleep apnea or poor sleep hygiene," says Dr. Ram.

(Related: 5 Ways Poor Sleep Affects the Body)