Whether you’ve caught a cold or simply need to rest, short-term muscle weakness happens to almost everyone. Even a hard workout can attribute to muscle weakness.
But if you develop persistent muscle weakness, or muscle weakness with no apparent cause or explanation, it may be a sign of an underlying health condition.
Muscle weakness is a lack of muscle strength; muscles may not contract or move as easily as they should.
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Your muscles contract when your brain sends a signal through your spinal cord and nerves. If your brain, nervous system, muscles or the connections between them are injured or affected by disease, your muscles may not contract normally, causing muscle weakness. Here are some typical causes.
As you age, muscles tend to lose strength and bulk and become weaker.
Physically inactive people can lose as much as 3 to 5 per cent of their muscle mass each decade after age 30. Even if you are active, you will still experience some muscle loss. This is called age-related sarcopenia.
It can be frustrating to realise you can’t do the things you could when you were younger. However, in many cases, it’s still possible to increase muscle power and strength – or at least prevent further weakening – with a careful and safe exercise routine.
If your doctor suspects sarcopenia, he/she may test for it by seeing how fast you can walk.
Lack of use
Deconditioning is one of the most common causes of muscle weakness and can be bought on by a sedentary lifestyle. If muscles are not used, then the fibres within them are partially replaced with fat, causing muscle wasting.
Muscle wasting causes the muscles to tire much quicker than when they were fit but the condition is reversible with sensible, regular exercise.
Muscle power is greatest and recovery times are shortest in our 20s and 30s. However, building of muscles through regular exercise can be done at any age. Many successful long-distance runners are aged over 40. Muscle tolerance for prolonged activity such as marathon running remains high for longer than the powerful, short-burst activities such as sprinting.
Infections and illness
Colds and flu are among the most common causes of temporary muscle fatigue, usually due to inflammation.
If the inflammation is severe, such as with a bad case of influenza, the weakness can last longer than other flu symptoms.
Some medications, such as prednisone and cholesterol-lowering statins, can cause muscle weakness. This usually starts as tiredness or fatigue and can worsen. Check with your doctor if you experience these problems.
When a muscle is damaged, bleeding inside the tissue can cause swelling and inflammation. This makes the muscle weaker and usually painful to use. See a doctor if your injury gets worse.
Regular stretching and exercises can help to keep your muscles strong and prevent future injuries.
Some conditions that affect the nervous system can cause muscle weakness. These conditions are often chronic and affect the way nerves transmit messages to the muscles.
Cervical spondylosis: Age-related changes to the cushioning spinal disks in the neck can cause cervical spondylosis. This puts extra pressure on nerves, resulting in muscle weakness.
Guillain-Barré syndrome: This rare neurological disorder can cause mild to severe muscle weakness.
Botulism: This rare condition occurs due to exposure from botulinum toxin. It also causes progressive muscle weakness.
Multiple sclerosis: This autoimmune disorder occurs when the immune system attacks and damages the nerves. Signs and symptoms of MS vary widely, but they often include numbness or weakness in one or both arms and legs.
Myasthenia gravis: This autoimmune disorder causes the immune system to attack the muscles, which can affect movement as well as breathing.
Amyotrophic lateral sclerosis: Known as ALS, this can cause progressive muscle weakness.
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Anaemia occurs when a person’s haemoglobin levels are low, often due to an iron deficiency. It has many causes, including heavy periods, poor diet, blood loss, pregnancy, genetic conditions, infections and cancers. It reduces the blood’s capacity to carry oxygen to muscles, so they tire more easily.
Other symptoms of anaemia include:
- shortness of breath
- cold hands and feet
- an irregular heartbeat.
If your muscles get weak suddenly, it might be a stroke. Most of the time, muscle weakness related to a stroke will affect one side of your body and not the other. You may also notice:
- blurred vision
- trouble walking or talking
- loss of balance and/or coordination
Underactive thyroid (hypothyroidism)
If you have an underactive thyroid, you often feel generalised tiredness or fatigue. If left untreated, it can lead to muscle degeneration and wasting, which can be severe and hard to reverse.
Hypothyroidism is a common condition that can be identified with a blood test.
Other symptoms include:
- weight gain
- feeling cold
- dry skin and hair
- a slow heart rate
- joint and muscle pain
- depression or mood disorders.
Depending on the cause, weakness may occur in one muscle, a group of muscles or all the muscles, and may be accompanied by pain, atrophy, cramping or other types of muscular symptoms.
To diagnose the underlying cause, a doctor will discuss your symptoms, medical history and what makes the symptoms worse or better.
Because muscle weakness can be due to serious diseases, failure to seek treatment can result in serious complications and permanent damage.
Have you ever experienced muscle fatigue? Is there anything you have found that reduces the discomfort or frustration? Share your thoughts in the comments section below.
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Disclaimer: This article contains general information about health issues and is not advice. For health advice, consult your medical practitioner.