4 Reasons You're So Tired After a Workout and What to Do About It

It's normal for you to feel tired after exercise, but there are things you can do to help you feel less exhausted after your next workout.
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Exercise should make you feel energized — not exhausted. But you're bound to feel lethargic after your workout from time to time.

When you exercise, you burn calories and expend energy. Depending on the length and intensity of your workout, you're physically stressing your body, which means you need water, nutrients and rest to recover. Here are some reasons you might feel especially tired after a workout and what you can do about it.

Read more:Exercise Burnout is Real — Here's How to Avoid It

Causes of Tiredness After a Workout

Many different factors can contribute to that sluggish feeling you're experiencing after working out. Some of the most common culprits include:

1. You're Pushing Yourself Too Hard

While it may sound obvious, the more intense your fitness routine, the more exhausted you'll typically feel after a workout. During low- to moderate-level exercise, the body harnesses energy from a molecule called adenosine triphosphate, or ATP, which uses oxygen to keep you moving, according to the University of New Mexico. Staying at moderate intensity allows you to work out while also effectively recovering afterward.

When your routine is too strenuous, however, the demand for ATP is higher, and it can leave your energy reserves depleted. That's why you may feel extreme fatigue after a really grueling training session.

2. You're Not Eating Correctly

Keeping your body properly nourished helps you feel good during and after exercise. Your diet has a direct effect on your muscles' ability to recover after a workout and on your energy levels after the fact.

Each day, you'll want to eat a whole food-based balance of carbs, healthy fats and protein, according to the Mayo Clinic. Before you sweat, opt for a fast-digesting carb snack, like bananas or oatmeal. Then, follow your workout with some protein and carbohydrates to support muscle repair and rebuilding.

Read more:4 Trainers Share the Pre-Workout Foods They Eat to Boost Their Performance

3. You're Not Drinking Enough Water

Regardless of your fitness level or preferred exercise, drinking enough water during and after your workout is important. When you exercise, your body can lose large amounts of fluid through sweat.

As a result, it's easy to become dehydrated if you don't drink water frequently, according to the University of Utah. When the body reaches a state of dehydration, tiredness or lethargy can occur and your muscles can't adequately recover.

4. You May Have a Medical Condition

In most cases, feelings of fatigue after exercise are easily improved by modifying your pre- and post-workout routine or by altering your fitness regimen. However, this isn't always the case.

Certain medical conditions make it harder to recover from a workout, including diabetes, chronic fatigue syndrome, COPD, multiple sclerosis and sleep apnea, according to the Mayo Clinic. Issues with your thyroid or heart may also be to blame. If you have any concerns, it's best to speak to your physician so that these conditions can be ruled out.

Read more:160 Exercise Statistics You Should Know

Why You Might Feel Sleepy After a Workout

It's important to differentiate between feeling tired or worn down after exercise and feeling the need to go back to sleep. While it may seem like splitting hairs, distinguishing between the two sensations can help you hone in on their root cause.

If your bed is calling after a workout, one of these three things may be why.

1. The Time of Day

Your body's natural circadian rhythm plays a role in the time of day that's best for you to work out. That internal clock, which is influenced by light and darkness, is involved in regulating your internal temperature, blood pressure and heart rate, according to the National Institute of General Medical Sciences.

These, in turn, influence your ability to complete and recover from a workout. Just as a night owl may have a hard time focusing on a work-related task in the early-morning hours, an early bird may become more easily exhausted by a late-night workout. Listen to your body's natural rhythms to avoid exhaustion.

2. Inadequate Sleep

Sleep and exercise go hand in hand. Regular exercise has been shown to improve sleep quality and feelings of fatigue during the day, according to Johns Hopkins Medicine. On the other hand, failure to get an appropriate amount of sleep the night before a workout can cause the same amount of exercise to seem more challenging.

In addition, getting enough sleep replenishes your energy reserves, according to the National Sleep Foundation. A sleep-deprived individual who already lacks energy and attempts to work out can become extremely sleepy after exercising.

3. Possible Medical Conditions

Certain diagnoses, like sleep apnea, can lead to feelings of sleepiness, according to the National Sleep Foundation. Exercising with one of these can further exacerbate your fatigue and make you feel as if returning to bed is the only option.

Taking certain supplements or medications can also contribute to the problem. Consult your health care provider early on to help you manage your sleepiness and make regular exercise more manageable.

Read more:10 Surprising Ways Sleep Affects Your Whole Body

5 Ways to Reduce Tiredness After Exercise

In most cases, a few simple changes to your daily routine can help improve or prevent fatigue and sleepiness after your workout. Try these five tips to improve your wellbeing after you exercise.

1. Listen to Your Body

Even if you're only exercising once or twice a week, don't blame yourself for getting tired. Instead of forcing yourself to march back into the gym, take the cues your body is giving you. This way you won't feel overly exhausted post spin class.

When you're tired, your body is demanding rest and nutrients to rebuild your muscles and energize you, according to the National Sleep Foundation. Although your workout might have been what pushed you over the edge, chances are you're neglecting your body before you even hit the gym.

2. Eat Before and After Your Workout

It's imperative to eat nutritious foods both before and after you exercise to fuel your body and replace lost calories, vitamins and minerals. Be sure to avoid eating too soon before your exercise routine, however, as this may lead to stomach discomfort.

If you plan on exercising for less than an hour, eat carbohydrates that will provide a quick burst of energy, like a handful of grapes or a small amount of fruit juice. If you're working out for longer than an hour, a bowl of Greek yogurt with a handful of granola can help provide you with the energy to sustain your routine.

After your session, refuel your body with a snack or meal that contains both protein and carbohydrates, like oatmeal with fruit and almond butter. This will replace the glycogen stores that have been depleted during exercise, providing an energy boost.

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3. Hydrate Properly

Staying hydrated is crucial to preventing dehydration as you sweat off fluid while you exercise. This involves drinking plenty of fluids before, during and after your workout.

Drink 2 to 3 cups of water two hours before exercise. Have a cup five to 10 minutes before your session begins and then 1 cup for every 15 to 20 minutes of exercise, recommends the University of Colorado Hospital.

4. Get Plenty of Sleep

If you've been burning the candle at both ends, exercise might be impossible. If you're spending your nights studying, working or taking care of your family instead of sleeping, you're depriving your body — and this can make you feel even more tired after a workout.

Get seven to nine hours of sleep a night to allow your muscles to rest and rebuild, recommends the National Sleep Foundation. Getting too little or too much sleep can lead to tiredness after a workout (not to mention throughout the rest of the day).

Read more:10 Habits That Are Ruining Your Sleep (and How to Fix Them)

5. Talk to Your Doctor

In rare cases, fatigue or exhaustion may be the result of a medical condition. If you have any medical symptoms in addition to your exhaustion after exercising, contact your doctor.