7 causes of muscle aches

If you’re sore after exercise, your muscle pain is easily explained. If it arises out of the blue, it could be one of these causes.

By Todd Hartley | Jun. 18, 2021 Medically reviewed by Jesse P. Houghton, MD, FACG

Almost everyone knows what muscle pain feels like. Whether it’s sore pecs and deltoids after a weightlifting session or aching muscles from an illness like the flu or Rocky Mountain spotted fever, it’s hard to make it through life without muscle aches every now and then. In most cases, such as with exercise or illness, the causes of muscle aches are easy to identify. But sometimes, the answers aren’t so simple, and muscle aches can become chronic and life-altering. That’s when it’s time to see a healthcare provider and figure out what’s really going on.

7 causes of muscle aches

Part of the reason muscle pain, or myalgia, is so common is because it has so many causes, both physical and emotional, and it can involve single muscles, groups of muscles, or even someone’s entire body. Treating muscle pain correctly depends on the cause, so it’s important to get the correct diagnosis if the cause isn’t readily apparent. Here are some of the most common causes of muscle aches, pains, and soreness.

1. Exercise and activity

If you play sports, lift weights, jog, hike, bike, or even work in your garden, chances are you’re familiar with the connection between muscle overuse and pain. Your muscles could be straining or cramping in the middle of a workout or a long run—a condition called acute muscle soreness —and the next day, you might feel even worse.

“Let’s say you haven’t done anything all week, and you’re the weekend warrior, and then, two days later you feel like you got hit by a Mack truck. Well, that’s something called delayed-onset muscle soreness,” says Naresh Rao, DO, the founder and CEO of MAX Sports Health and head physician for the U.S. men’s water polo team.

Acute muscle soreness is most often caused by a buildup of lactic acid, which is produced by your muscles when your body breaks down carbohydrates to use for energy (glycolysis) in excess of the available oxygen. This is often the case during intense workouts when the muscles need more oxygen than your lungs and blood can provide. The lactic acid can build up quickly, leading to acute muscle soreness during or immediately after the activity. People who suffer from claudication, which is pain caused by too little blood flow to the muscles during exercise, may also experience acute muscle soreness. The pain typically goes away when they stop exercising. Whereas the build up of lactic acid can occur in healthy individuals, claudication can be a sign of a vascular problem and should be evaluated by a doctor.

Delayed-onset muscle soreness, which was once thought to be caused by lactic acid, as well, is actually the result of tiny injuries to your muscle fibers. When your muscles are called on to do more than they’re accustomed to, they can suffer microscopic damage that can lead, a day or two later, to inflammation, stiffness, and muscle soreness.

Fortunately, activity-related muscle aches usually resolve quickly and, in most cases, aren’t something to worry about. “Muscle pain that occurs after exercise is pretty normal in most people,” says David Dickoff, MD, a neurologist and assistant clinical professor of neurology with Mount Sinai Hospital. “In fact, it’s often a good feeling, a feeling people like to have. It’s a sense of fatigue in the muscles that lets you know that you had a good, aggressive day of skiing, or a nice softball game, or a nice long walk.”

2. Stress, anxiety, and tension

When you’re stressed out or anxious, your muscles can tense up suddenly or for long periods of time. The American Psychological Association calls this “almost a reflex reaction to stress—the body’s way of guarding against injury or pain.” Long periods of tension due to chronic stress can lead to muscle aches, which is why many stressed-out people suffer from shoulder, neck, and back pain. Muscle tension can also contribute to joint pain and other stress-related conditions like migraine headaches and mental health issues.

To help alleviate stress-related muscle aches, physicians often recommend simple at-home measures such as getting more exercise, taking breaks from sitting at a desk to get up and move around, meditation and other relaxation techniques, and gentle stretching. You can also make ergonomic modifications like upgrading to a better chair or working at a standing desk. If it’s possible, getting more sleep may also help ease muscle pain. Meditating for up to 30 minutes before bedtime has been shown to help some people sleep better.

3. Injuries

When muscles are extended or flexed beyond what they’re used to, they can begin to tear. In many cases, when the tears are microscopic and don’t involve the larger muscle, the resulting muscle strain, or pulled muscle, is a simple injury that resolves immediately or in a day or two. However, more serious cases, which can involve a partial or complete tear of the entire muscle, can be extremely painful and often debilitating. Sprains, which involve connective tissue like ligaments and tendons, can also cause sore or painful muscles.

When a bone gets broken or a muscle, joint, or soft tissue gets injured, the muscles surrounding the injured area are often affected, as well. This may occur as the body tries to compensate for the injured part of your body, which might not be working the way it should. The additional strain on the surrounding muscles and bones will often lead to significant muscle spasms and soreness.

4. Underlying medical conditions

Many types of illnesses, infections, and autoimmune diseases can cause muscle pain, but the biggest culprit is one that most people wouldn’t guess.

Dr. Dickoff says with restless leg syndrome, or RLS, patients often mistake the uncomfortable feeling as “cramps”—even though they’re not truly cramps. “Restless leg syndrome is a really important consideration for patients with myalgias,” he says, “because it can be genetic, and it may be present in up to 15% of the population, which means that in America some 35 million people may experience RLS.”

Immune system diseases, such as lupus and multiple sclerosis, can cause arthritis (inflammation of the joints), or myositis, an inflammation of the skeletal muscles you use to move your body. This can lead to muscle pain, fatigue, and muscle weakness. Muscle pain due to inflammation is also a common symptom of many bacterial and viral infections, such as coronavirus, viruses that cause the common cold, the flu, malaria, and the illnesses Lyme disease and Rocky Mountain spotted fever, both of which result from a tick bite.

Another common cause of myalgia is dehydration, which forces your body to pull fluids out of your tissues, leading to body aches and pains. Less common causes include high blood pressure, which can lead to circulation problems, limiting blood flow to muscles, and rapid weight loss, which can cause dehydration and thereby muscle cramps.

Other illnesses and conditions that can cause muscle pain include:

Amyotrophic lateral sclerosis (ALS, or Lou Gehrig’s disease)
Certain cancers, such as sarcomas and leukemia
Chronic fatigue syndrome
Compartment syndrome
Dermatomyositis
Diabetes
Hypothyroidism
Muscular dystrophy
Myofascial pain syndrome
Peripheral artery disease
Rhabdomyolysis
Rheumatoid arthritis
Spinal muscular atrophy
Thyroid disorders

If you have persistent muscle aches without an obvious cause, it may be a good idea to talk to a healthcare provider about these conditions.

5. Fibromyalgia

Characterized by the Centers for Disease Control (CDC) as “a condition that causes pain all over the body (also referred to as widespread pain), sleep problems, fatigue, and often emotional and mental distress,” fibromyalgia affects about 4 million adults in the U.S. The exact cause of fibromyalgia isn’t known, but people with the condition experience numerous muscle-related symptoms like widespread pain and stiffness, tingling or numbness in the hands and feet, and pain in the face and jaw, including temporomandibular joint (TMJ) syndrome.

“Fibromyalgia manifests with multiple pains in various areas,” says Dr. Rao. “You pretty much have what we call trigger points. There’s a whole map of them all over your body, and if you have multiple ones affected, ranging from hip pain to shoulder pain, and your elbows hurt, and all your muscles hurt, then it could definitely be a sign that you want to get that checked out.”

Fibromyalgia can often be treated effectively through medications and self-help measures like exercise, stress-management techniques, good sleep habits, and cognitive behavioral therapy (CBT), which can help treat underlying mental health issues like depression or anxiety.

6. Polymyositis or polymyalgia rheumatica

Taking its name from the Greek words poly (many), myo (muscle), and itis (inflammation), polymyositis is an inflammatory disease that causes chronic inflammation and muscle weakness, especially in the muscles closest to the center of the body, like the thighs, hips, back, neck, and shoulders. According to The Myositis Association, the muscle weakness associated with polymyositis usually happens over days, weeks, or months and can affect your ability to walk, run, climb stairs, or get back up after a fall.

Polymyalgia rheumatica (or PMR) is a similar inflammatory muscle disease whose name means, literally, “many muscle pain that flows.” Polymyalgia rheumatica causes muscle pain and stiffness, particularly in the shoulders and hips.

“Polymyositis simply means you have inflammation in many muscles,” says Dr. Dickoff. “Polymyalgia means that you have aching in many muscles [as the actual muscles in PMR are normal].”

The causes of polymyositis and polymyalgia rheumatica aren’t known, and there are no cures, but treatment with medications, physical therapy, lifestyle changes, and home remedies can help ease symptoms and help weakened muscles regain some of their strength.

7. Medications

Myositis (inflammation of muscle cells) is a side effect of a number of medications and therapies, including chemotherapy, radiation therapy, statins used to lower cholesterol, and high blood pressure medications, such as angiotensin-converting enzyme (ACE) inhibitors. If you’re on a new medication or undergoing chemo or radiation therapy, and you experience muscle pain, be sure to seek out a healthcare provider’s medical advice before stopping your treatment.

When to see a doctor for muscle pain

In most cases, if muscle pain is related to increased activity or a minor injury, it should go away shortly and can probably be treated at home with simple measures. But if your muscle pain lasts for more than three days or you have severe, unexplained muscle pain, make an appointment to see a medical professional as soon as you can.

“Muscle aches where you have loss of motion should be a red flag,” says Dr. Rao. “For example, you may have a little neck tension, but if you feel like you can’t move your neck without sharp pain, that’s important. And another one is if the pain is just out of control. We use the scale of 0 being no pain and 10 being the worst pain you’ve ever had. Once you start getting to 5 or 6, and if it’s been lasting more than one or two days, you definitely want to have someone take a look.”

Other symptoms that warrant a call to the doctor include:

Any sign of infection, such as swelling or redness around the sore muscle
A tick bite or a rash, especially the telltale bullseye rash of Lyme disease
Muscle pain that might be caused by a medication you’re taking
Poor circulation in the affected area (usually causes a red, purple, or blue skin color and a colder temperature).
Sudden weight gain or water retention (urinating less frequently)

Call 911 or get yourself to a hospital emergency room if you experience any of the following along with your muscle pain:

Trouble breathing or dizziness
Extreme muscle weakness (especially one sided)
High fever
Very stiff neck or severe headache
Vomiting

How to treat muscle aches

Muscle pain and soreness from activity, exercise, or minor injury often requires little more in the way of treatment than the tried and true RICE (rest, ice, compression, elevation) method. Give your sore muscles time to recover, put an ice pack on them, keep the affected area elevated, and you should recover just fine. Many people also get relief from over-the-counter anti-inflammatory pain relievers like Advil (ibuprofen), Tylenol (acetaminophen), aspirin, and Aleve (naproxen).

If at-home measures alone aren’t enough to treat muscle pain, doctors may prescribe stronger pain-relieving medications, including:

Regular exercise and gentle stretching can help restore muscle tone and ease soreness. If you don’t get much exercise, start a new regimen slowly and build up to more intense activity over time to avoid exercise-induced muscle pain. Massages can be effective at relieving pain, as well, especially pain caused by overuse or fibromyalgia. Relaxation techniques, acupuncture, meditation, yoga, staying well hydrated, and getting more and better sleep may also help. Work with your healthcare provider to find the method that works best for you.