Extreme Fatigue After Exercise? Here’s What Your Body’s Trying to Tell You

Don't sweat it: Mild fatigue after exercise — on top of being sweaty, a bit sore and tuckered out — is A-OK, especially if you're new to exercise. There's a limit, though. If you feel completely exhausted after a workout, it could be a sign of a health problem — or that you overdid it. So, where's the line?

"It is normal to feel a bit winded, slightly tired or even mildly sore after, depending on the nature of the workout," Tim Bish, CPT, lead coach at Row House Chelsea in New York City, tells LIVESTRONG.com. "But these symptoms shouldn't feel overwhelming or unmanageable."

How long does workout fatigue last? In general, "normal" fatigue should last a few hours or overnight. But a good night's sleep should allow your body and brain to bounce back, Bish says. Drinking water, eating, stretching and/or taking a hot shower or bath should also help, he says.

Some tightness in the muscles for one to three days, known as DOMS (delayed onset muscle soreness), is also normal, according to the International Sports Science Association (ISSA). On the other hand, extreme fatigue tends to linger.

"Excessive fatigue will often not respond to these tactics and should be monitored carefully," Bish says. If you feel like you're not recovering well, or you're more sleepy than you should be post-workout, here's what might be going on — plus, how to avoid feeling fatigue after a workout in the future.

Pushing beyond your capabilities during your workout (use this guide to tell if you're working out too hard or not hard enough) can leave you feeling completely gassed and add days to your recovery time.

In extreme cases, it can also cause a concerning amount of damage to your muscles, resulting in a rare but dangerous condition called rhabdomyolysis, according to Harvard Health Publishing.

This can happen when intense exercise causes muscle tissue breakdown beyond what the body can handle. However, the condition isn't all that common among most regular exercisers, but does occur in more advanced athletes like marathoners, bodybuilders and CrossFitters.

When muscles break down, a substance called myoglobin is released into your bloodstream, according to the National Library of Medicine (NLM). The kidneys then filter it from the blood. If there's too much, though, it can overwhelm and damage kidney cells.

If you feel weak and nauseous after your workout or have dark-colored urine, you might have rhabdomyolysis. Other symptoms include joint pain, muscle fatigue in your legs or other body parts and weakness.

Increase your workout intensity and duration slowly over time and stick to low-impact workouts when you're sore, says certified personal trainer and therapeutic exercise specialist Erin Nitschke, CPT, EdD.

"There's no one-size-fits-all approach when it comes to workout programming [or recovery]," she says. "The biggest key to success is starting slowly and choosing activities that are enjoyable and fulfilling."

As a general rule, moderate-intensity exercise on most days of the week is best, says Kush Patel, MD, a sports medicine doctor at Sports Medicine of Central Pennsylvania-UPMC.

Over time, you want to work up to reaching the Physical Activity Guidelines for Americans recommendation of two days of total-body strength training per week, plus at least 150 minutes of moderate-intensity or 75 minutes of vigorous-intensity aerobic activity each week.

Overtraining syndrome — as the name implies — occurs over time from too much training, according to a March 2012 guide in ‌Sports Health‌.

"Overreaching" is basically a short-term version of overtraining. Both issues come from too much exercise and not enough rest. However, overtraining happens over the course of a month or more, while overreaching may occur after a single, intense workout.

Per the March/April 2015 issue of ‌ACSM's Health and Fitness Journal‌, symptoms of overreaching usually resolve quickly once you stop exercising and get more rest. However, the symptoms of overtraining can last two months or more.

What are the symptoms of over-exercising? If you have either problem, you'll notice you're constantly fatigued and sore. You might also get sick more often due to a suppressed immune system.

Your mental health is affected by overtraining and overreaching, too. Your sleep can be disrupted, you may experience symptoms of depression or you can experience the absence of menstruation (amenorrhea).

Nitschke recommends fitting in at least one full rest day between vigorous workouts. A general rule of thumb is to rest a muscle group for at least 24 to 48 hours after training it.

Prioritizing sleep can help, too. Try to keep a consistent sleep schedule, aiming for seven to nine hours of sleep per night, Nitschke says. (If you find it challenging to sleep after a workout, we can help.) With plenty of rest, you might not feel so tired after working out — or in general.

Working out makes you sweat, which can feel good if you're properly hydrated. However, if you're not prepared for your workout and you lose too much fluid, you can become dehydrated.

Thirst isn't the only symptom of dehydration, according to the NLM. You might notice you're actually sweating and urinating less, as your body attempts to preserve fluids. You could also get tired, feel dizzy, have a headache or experience a decrease in performance.

In serious cases, you can be confused and even faint. Your heartbeat can become rapid or irregular, and it's possible to go into shock, per the NLM.

Heat complicates dehydration. Because your body uses sweat to cool off, exercising in a hot environment can make you lose fluids more rapidly. If you're going to work out somewhere exceptionally warm, make sure to hydrate more than you usually would.

Hydrate before, during and after a workout, even if you don't necessarily feel thirsty. Aim for about 20 ounces a couple of hours before your workout, plus 8 ounces 30 minutes before you begin.

Drink 7 to 10 ounces every 10 to 20 minutes during your sweat session, then sip on another 8 ounces within the 30 minutes post cooldown, according to the American Council on Exercise. And make sure to stay hydrated throughout the rest of the week by following these water consumption tips.

Be careful not to over-hydrate, though, as this can result in hyponatremia, per the Mayo Clinic. Drinking too much water too quickly can lead to a decrease in sodium and brain swelling. This condition is rare but can result in serious health consequences.

Inadequate nutrients or eating too few calories can cause your energy levels to take a nosedive. Hypoglycemia, or low blood sugar below 70 mg/dl, can also happen as a result of intense exercise, according to the American Diabetes Association (ADA).

"This is when blood glucose levels drop too low to support the energy demands of a person's body. The condition can affect people with and without diabetes," Dr. Patel says. "When you exercise, your muscles need more sugar to supply energy."

Your body uses up sugar that's stored in the muscles (called glycogen) and in your bloodstream to fuel all the cells that need it, per a March 2018 study in ‌Nutrients‌. Because of this, "moderate to intense exercise may cause your blood sugar to drop during exercise and for the next 24 hours following exercise," Dr. Patel says.

There is a wide range of symptoms of hypoglycemia, which may occur during or after your workout. Per the ADA, physical symptoms include shakiness, rapid heartbeat, nausea, headache or general weakness. There are also mental symptoms like confusion, anxiety, nightmares or mental fatigue. In extreme cases, you can have seizures. If you notice these signs, talk to your doctor.

To prevent low blood sugar during or after exercise, eat something after working out with carbohydrates within three hours of your workout, Dr. Patel says. You probably don't need a full meal, but a quick snack with 20 to 30 grams of carbohydrates, such as one medium apple, should help. You can also have a sports drink that contains carbs.

In general, eating enough calories will give you the energy you need to get through workouts and the fuel your muscles need to recover. Nitschke recommends eating an overall well-balanced diet that includes lean proteins, healthy fats, complex carbohydrates and enough calories. (Here are six signs you're not eating enough.)

If you think you might be overdoing it, that's a red flag. Listen to your body, and if you're uncertain if you're over-exercising it, talk to a trainer for personalized advice about how to tailor your workout intensity, length and frequency.

Or if you notice you're feeling exhausted after workouts and the next day fairly regularly, keep a symptom log to share with your doctor. Bish suggests seeking professional help immediately if you have:

• Difficulty breathing
• Recurring pain or discomfort
• Headaches
• Confusion
• Nausea and/or vomiting
• Heart palpitations
• Tingling
• Sustained pain
• Fatigue that's overwhelming or unmanageable

"Your doctor should always be a collaborator in your fitness regimen. Working out should ultimately make us feel stronger, more pliable and more energized," Bish says.

Only you can determine how severe your fatigue is. Are you a bit more tired than usual and maybe a bit sore, too? You might want to wait it out. Or does it go on for days with no signs of improvement? Talk to your doctor.

"Trust your instincts. If something isn't feeling right, don't wait to see how it goes," Bish says. Speak with your doctor so they can help you identify any conditions that may be impairing your ability to exercise and can help you create a plan to work around that safely.