From the Guidelines
Muscles most likely to twitch after consuming high amounts of caffeine and salt include eyelids, facial muscles, hands, calves, and feet. These muscles are prone to twitching due to the stimulant effects of caffeine, which increases neuron excitability and calcium release in muscle cells, as well as the disruption of electrolyte balance caused by high salt intake, particularly affecting sodium, potassium, and magnesium levels 1.
Key Factors Contributing to Muscle Twitching
- Caffeine intake: High amounts of caffeine can increase neuron excitability, leading to involuntary muscle contractions 1
- Salt intake: Excessive salt consumption can disrupt electrolyte balance, interfering with normal nerve-muscle communication and causing twitches
- Electrolyte imbalance: Sodium, potassium, and magnesium levels are particularly affected by high salt intake, contributing to muscle twitching
- Muscle type: Small, fine muscles with high nerve innervation, such as those around the eyes, are especially susceptible to twitching
Recommendations to Reduce Muscle Twitching
- Limit caffeine intake to less than 400mg daily (about 4 cups of coffee) 1
- Maintain proper hydration to help regulate electrolyte balance
- Reduce sodium consumption to under 2,300mg per day, as recommended by the American Heart Association 1
- Ensure adequate intake of potassium and magnesium through foods like bananas, leafy greens, and nuts If muscle twitches persist despite these measures, they may indicate an underlying medical condition requiring professional evaluation 1.
From the FDA Drug Label
Signs and symptoms reported in the literature after caffeine overdose in preterm infants include ... fine tremor of the extremities, hypertonia, opisthotonos, tonic-clonic movements, ... The muscles most likely to twitch after consuming high amounts of caffeine are those in the extremities, as evidenced by fine tremor and tonic-clonic movements.
- Extremities muscles, such as hands and feet, may exhibit twitching or tremors.
- Tonic-clonic movements suggest that muscles throughout the body, including those in the arms and legs, may be affected. 2
From the Research
Muscles Affected by Caffeine and Salt
The muscles most likely to twitch after consuming high amounts of caffeine and salt are:
- Fast-twitch muscles, such as the extensor digitorum longus (EDL) muscle
- Slow-twitch muscles, such as the soleus muscle
Evidence from Studies
Studies have shown that:
- Caffeine potentiates the twitch responses of both soleus and EDL muscles in a dose-related manner, with the soleus being more sensitive 3
- Caffeine concentrations below 5 mmol l-1 potentiate twitch and tetanic force in both fast- and slow-twitch mammalian skeletal muscles primarily by increasing both the basal and stimulus-evoked release of Ca2+ from the sarcoplasmic reticulum 3
- Electrically-evoked twitch and tetanic tension were measured in isolated rat soleus muscle after exposure to caffeine, and twitch tension was potentiated, reaching a peak of 150% of Resting Tension at 0.5 mM caffeine 4
- The ergogenic effects of caffeine on power output were higher in muscles with a slower fiber type, such as the soleus muscle 5
- Caffeine concentrations below the physiological maximum can directly potentiate skeletal muscle power output, with greater gains likely in activities powered by slower muscle fiber type 5
Comparison of Fast- and Slow-Twitch Muscles
Comparing the effects of caffeine on fast- and slow-twitch muscles:
- The soleus muscle is more sensitive to twitch potentiation and contractures evoked by caffeine than the EDL muscle 3, 4, 6
- The EDL muscle is more sensitive to 4-chloro-m-cresol, a substance that induces a dose-dependent caffeine-like transient contractile response, than the soleus muscle 7
- The effects of caffeine on contractile properties of slow-twitch and fast-twitch rat muscles are temperature-dependent, with the soleus muscle showing a higher extent of potentiation of twitch tension by caffeine at 20 degrees C than at 35 degrees C 6