From the Guidelines
Caffeine doses exceeding 32 mmol litre−1 are required to guarantee muscle twitching, as this is the highest concentration tested in the static cumulative caffeine test that produces a sustained increase of at least 2 mN in baseline force from the lowest force reached 1. To induce muscle twitching, the amount of caffeine needed can vary significantly between individuals, but research suggests that high doses are typically required.
- The static cumulative caffeine test, as outlined in the European Malignant Hyperthermia Group guidelines, involves increasing caffeine concentrations stepwise to determine the threshold concentration that produces a sustained increase in baseline force 1.
- The test uses caffeine concentrations of 0.5,1.0,1.5,2.0,3.0,4.0, and 32 mmol litre−1, with each successive concentration administered after the maximal contracture plateau induced by the previous concentration has been reached or after exposure for 3 min 1.
- The result of this test is reported as the threshold concentration, which is the lowest concentration of caffeine that produces a sustained increase of at least 2 mN in baseline force from the lowest force reached 1.
- Individual factors, such as body weight, tolerance level, metabolism rate, and pre-existing medical conditions, can significantly influence sensitivity to caffeine and the likelihood of experiencing muscle twitching at lower doses.
- Caffeine stimulates the central nervous system and can increase neuromuscular excitability, leading to involuntary muscle contractions or twitches at high doses 1.
- If muscle twitching persists after caffeine consumption, it is advisable to reduce caffeine intake to minimize potential adverse effects.
- It is essential to note that the amount of caffeine required to induce muscle twitching can vary significantly between individuals, and the static cumulative caffeine test provides a standardized method for determining the threshold concentration 1.
From the FDA Drug Label
These include: ... (5) increased skeletal muscle tone, ... Serious toxicity has been associated with serum levels greater than 50 mg/L
The amount of caffeine required to induce muscle twitching is not directly stated in the FDA drug label. However, increased skeletal muscle tone is mentioned as one of the effects of caffeine, and serious toxicity, which may include muscle twitching, is associated with serum levels greater than 50 mg/L.
- Key points:
From the Research
Caffeine and Muscle Twitching
- The amount of caffeine required to induce muscle twitching is not explicitly stated in the provided studies, but some studies suggest that high doses of caffeine can cause muscle twitching as a side effect 3, 4.
- A study on frog single muscle fibers found that 1 mM caffeine can induce twitch potentiation, but the equivalent dose in humans is not specified 5.
- Another study on mouse muscles found that caffeine can convert activity-induced shortening of half-relaxation times into prolongations, but the dose of caffeine used is not specified 6.
- The International Society of Sports Nutrition recommends a caffeine dose of 3-6 mg/kg body mass for exercise performance, but does not mention muscle twitching as a specific effect 7.
- High doses of caffeine (e.g. 9 mg/kg) are associated with a high incidence of side-effects, but it is not clear if muscle twitching is one of them 7.
Caffeine Dosage and Side Effects
- The general consensus is that caffeine doses up to 400 mg/day in healthy adults are not associated with adverse effects, including muscle twitching 3, 4.
- However, individual tolerance to caffeine and sensitivity to its effects can vary greatly, and some people may experience side effects such as muscle twitching at lower doses 3, 4.
- The studies suggest that caffeine can have different effects on different types of muscles, and that the dose and timing of caffeine ingestion can influence its effects on muscle function 5, 6.