Logan Steele
There are many reasons why muscles shake, and it is usually a normal response to strenuous exercise. Muscle shaking can be caused by muscle fatigue, low blood glucose, stress, or anxiety. When you exercise, your brain sends signals to your muscles through the nervous system, recruiting the muscle fibres needed to complete the activity. The more strenuous the activity, the more motor units are needed to complete the task. As more motor units become fatigued and drop out, the muscle contractions become more synchronous and less smoothly organised, resulting in a trembling movement.
| Characteristics | Values |
|---|---|
| Cause | Muscle fatigue, low blood glucose, stress, anxiety, alcohol consumption, caffeine intake, medication, nervous system attempting to recruit more muscle fibres |
| Prevention | Lowering workout intensity, reducing number of reps, increasing rest time between sets, eating a nutritious meal before working out |
| Interpretation | Positive sign of a successful workout, a “yellow light” to slow down, a sign of the brain attempting to reconnect with the specific area being worked on |
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Muscle fatigue
The underlying causes of muscle fatigue can be classified as either central or peripheral. Peripheral fatigue is produced by changes at or distal to the neuromuscular junction, which is the site where nerves and muscles interact. On the other hand, central fatigue is related to changes within the central nervous system (CNS), which can affect neurotransmitter concentrations and impact the ability to generate muscle contractions.
There are two main causes of muscle fatigue: neural fatigue and metabolic fatigue. Neural fatigue occurs when a nerve's ability to generate a sustained signal is limited, impacting the force of muscular contractions. This is more common in novice strength trainers or individuals performing extremely powerful contractions. Metabolic fatigue, on the other hand, is caused by a shortage of fuel (substrates) within the muscle fibres or the accumulation of substances (metabolites) that interfere with muscle contractions. These metabolites, such as lactic acid and inorganic phosphate, can directly or indirectly affect the release of calcium, which is essential for muscle contractions.
The symptoms of muscle fatigue include muscle weakness, myalgia (muscle pain), shortness of breath, muscle twitching, trembling, and cramps. In some cases, it can also lead to an inappropriate rapid heart rate response to exercise, known as an exaggerated cardiorespiratory response. It is important to note that muscle fatigue should not be confused with muscle weakness, although weakness can be an initial symptom. As muscle fatigue progresses, individuals may lose their grip strength or become unable to perform certain movements, such as lifting or pushing with their arms or legs.
To prevent and manage muscle fatigue, it is crucial to stay hydrated, maintain a healthy diet, and ensure proper nutrition before workouts. Additionally, warming up, stretching, and gradually increasing the intensity of exercises can help protect against muscle fatigue and improve recovery. In more severe cases of muscle fatigue, medical attention may be required, and doctors may recommend physical therapy or prescribe medications to address the underlying cause.
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Low blood glucose
Muscle shakes during or after a workout can be caused by low blood glucose, also known as hypoglycemia. Hypoglycemia can occur when the body does not have enough nutrients to fuel the muscles, leading to a depletion of glucose or blood sugar. This can be particularly common when working out on an empty stomach.
Certain foods can also trigger a sudden spike and subsequent drop in blood sugar levels, leading to hypoglycemia. Simple carbohydrate foods like white rice, potatoes, white bread, cake, and pastries are examples of such foods. After bariatric surgery, the body may absorb sugars more rapidly, stimulating excess insulin production and resulting in hypoglycemia.
To prevent muscle shakes due to low blood glucose, it is recommended to eat a nutritious meal at least an hour before working out. Snacks high in carbohydrates or natural sugars, such as peanut butter or orange juice, can help stabilize blood sugar levels and prevent muscle shaking caused by hypoglycemia.
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New movements
Trying a new movement or exercise can cause muscle shaking. This is because new movements require the activation of different muscle fibres and neuromuscular junctions. As these fibres and junctions activate for the first few times, they might twitch and shake until they become accustomed to the new stimulus. This is known as "muscle activation".
The more strenuous the activity, the more motor units are needed to complete the task. Motor units are made up of a motor neuron and muscle fibres. The longer you work out, the more these signals slow down and become less intense. These changes can make your muscles rapidly alternate between contractions and relaxations, resulting in tremors.
This shaking is not something to be ignored, but it also doesn't necessarily mean you need to stop your workout. Think of shaking as a "yellow light", a sign to slow down and be ready to take a break.
If you are practising a new movement, you may also experience shaking due to muscle fatigue. This is a common reason for tremors after exercise, as your muscles tire and your body activates more fibres to keep going. You may also experience muscle fatigue if you hold a muscle in one position for a long time.
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Stress and anxiety
Shaking or trembling is a common symptom of anxiety. When you experience anxiety, your body enters a fight, flight, or freeze mode, releasing stress hormones like adrenaline and cortisol. This results in heightened alertness and physical changes such as increased muscle tension and nerve activity, rapid heart rate, increased blood pressure, and increased blood flow to your muscles. The rapid contraction and relaxation of muscles can lead to a shaking or trembling sensation throughout the body, including the hands, legs, and voice.
While this physiological response is meant to protect you from danger, it can be uncomfortable and disconcerting. The good news is that there are strategies to manage anxiety shakes. Here are some techniques to help you regain control and calmness:
- Breathing exercises: Focusing on your breath can help prevent hyperventilation and reduce the likelihood of entering the fight, flight, or freeze mode. Deep breathing exercises, practiced regularly, can help you feel more grounded and reduce anxiety-related symptoms.
- Cognitive techniques: These techniques help shift your focus away from anxious thoughts and redirect your mind towards more calming or neutral patterns of thinking. This can be achieved through positive visualization, challenging negative thoughts with self-compassion, and using distraction techniques like simple tasks or hobbies.
- Progressive muscle relaxation: This technique focuses on contracting and then releasing different muscle groups, often combined with deep breathing. The goal is to get your body to relax and stop trembling. Gentle stretching can also help relieve muscle tension and reduce shaking.
- Physical activity and exercise: Exercise is a natural anxiety reliever. It releases endorphins, decreases cortisol, and reduces stress hormones while increasing natural mood boosters. Yoga, when practiced consistently, can help people with anxiety relax and experience fewer stress responses to triggers. Walking or light exercise can also help burn off excess adrenaline and calm your nervous system.
- Mindfulness and meditation: Mindfulness practices, including meditation, can help reduce stress and anxiety symptoms. Apps like Headspace offer guided meditations to promote awareness and relaxation. Practicing these techniques when you're calm can make them more effective when you need them during anxious moments.
- Lifestyle changes: Adopting a balanced diet, rich in nutrients, is essential for supporting brain health and regulating mood. Effective time management can also reduce overwhelm and avoid unnecessary stress. Incorporating regular breaks and relaxation techniques can help prevent stress accumulation and promote overall well-being.
- Therapy and medication: Engaging in cognitive-behavioral therapy (CBT) with a therapist can help address anxiety by identifying and altering negative thought patterns. Selective serotonin reuptake inhibitors (SSRIs) are a common and effective treatment option for anxiety, often used in conjunction with psychotherapy.
It's important to note that shaking can be a symptom of anxiety even if you don't have a diagnosed anxiety disorder. However, if you're experiencing persistent or severe shaking, it's recommended to consult a healthcare professional to determine the underlying cause and receive personalized treatment.
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Nervous system
Muscle shaking during exercise can be attributed to two main causes. Firstly, muscle shaking can occur when the muscles are tired or fatigued. Secondly, muscle shaking can be a result of attempting a new movement or lifting a heavier weight, indicating that the body is trying to do something it is not accustomed to. In both cases, muscle shaking is a sign that the nervous system is attempting to recruit more muscle fibres to accomplish the task at hand.
The nervous system plays a crucial role in muscle movement and coordination. When exercising, the brain sends signals through the nervous system to activate specific muscle fibres required for the activity. This process is known as muscle recruitment. The more strenuous the activity, the greater the number of motor units, which consist of a motor nerve cell (neuron) and the muscle cells it innervates, are needed to complete the task.
During intense exercise, some of these motor units can become fatigued and cease to function optimally. This leads to an asynchronous contraction and relaxation of the muscles, resulting in a trembling appearance. The motor units that are still functioning have to work harder, leading to a jerky and uncoordinated movement. This is why you may experience shaking during those last few reps of a challenging workout.
Additionally, muscle shaking can occur when attempting a new type of exercise or movement. In this case, the body needs to activate different muscle fibres and neuromuscular junctions, which may twitch and shake as they adjust to the new stimulus. This is often a temporary response as the body adapts to the new movement pattern.
It is important to note that muscle shaking can also be influenced by other factors such as nutrition, stress and anxiety, and in rare cases, medical conditions affecting the nerves. Experiencing muscle shakes during or after a workout is usually a normal response, but if it persists or interferes with your daily life, it may be advisable to consult a healthcare professional.
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Frequently asked questions
Your muscles shake when you're working out because they are constantly alternating between states of contraction and relaxation. This happens because your body is recruiting more muscle fibres to help you complete the task.
When your body experiences a new stimulus, it might require new muscle fibres and neuromuscular junctions to activate. As those fibres and junctions activate for the first few times, they might twitch and shake until they get accustomed to the new movement.
Involuntary muscle shaking after a workout is usually caused by muscle fatigue or low blood glucose. It could also be because you're isolating certain muscle groups, causing them to fatigue more quickly.
When you're stressed or anxious, your body experiences a state of "hyperarousal" or "hyperstimulation". This means your body is in a constant state of semi-stress response readiness, which can manifest as muscle shakes.
To prevent muscle shakes during a workout, you could lower the intensity of your workout, reduce the number of reps per set, or increase the length of time between sets. Eating a nutritious meal at least an hour before your workout can also help prevent muscle shaking.
