Professional Background Neurogenetic disorders, including myotonic dystrophy; therapeutics, including antisense approaches. Myotonia is a state of hyperexcitability in muscle fibers in which a voluntary contraction or electromechanical stimulation can provoke trains of repetitive action potentials. This causes delay in relaxation after a muscle contraction. The repetitive action potentials are generated by the muscle fibers, independent of any input from the motor neuron. Myotonia is caused by dysfunction of ion channels in the muscle membrane.