Fasciculations in Healthy Adults After Consumption of Caffeine: an Ultrasound Study

Fasciculations are clinically defined as spontaneous intermittent contractions of a portion of muscles [8]. They can also be assessed with electromyography and are classified as a result of spontaneous depolarization of a lower motor neuron leading to the synchronous contraction of all of the skeletal muscle fibers within a single motor unit [9]. On ultrasound examination fasciculations are classified as involuntary twitching of small parts of the muscle, lasting for 0.2 - 1.0 seconds [10]. They result from spontaneous discharges of motor nerves, but the etiology and the site of origin of these discharges remains still uncertain and is controversially discussed [11, 12]. Depending on the associated symptoms they may be a sign of lower motor neuron disorder. They are a hallmark of amyotrophic lateral sclerosis, a neurodegenerative disease affecting upper motor neurons in the brain and lower motor neurons in the spinal cord, especially when they are widespread [13, 14]. Fasciculations can also be a normal phenomenon that almost everyone has experienced occasionally in their lives or more frequently in healthy subjects after exercise [15]. It is controversially discussed if fasciculations above the knee should raise the suspicion of a disorder even if there are no other signs of lower motor neuron affection. In a recent Dutch study the prevalence and distribution of fasciculations in healthy adults was assessed with ultrasound and it could be shown, that strenuous physical exercise causes a temporary increase in fasciculations but only in lower leg muscles in healthy adults [14]. However the fasciculations were screened only for 10 seconds 30 minutes after exercise. It is well known that the observation time for fasciculations should be 2 minutes to decide if a muscle is "fasciculation-free" [15]. The aim of this study is to investigate if fasciculations also occur in muscles after caffeine consumption and if there is a difference between the muscles of the arms and legs.

3 STUDY OBJECTIVES AND DESIGN 3.1 Hypothesis and primary objective The hypothesis about the primary endpoint, the comparison of two proportions, can be examined by a Fisher exact test.

The null hypothesis of the primary endpoint is, that there is no difference in the proportions of fasciculations below and above the knee.

The alternative hypothesis of the primary endpoint states a difference in the proportions of fasciculations below and above the knee.

Secondary objective / endpoint: