Single fiber EMG abnormality Increased jitter at single fiber EMG Increased jitter at single fibre electromyography Increased jitter at single fibre EMG Increased jitter values are not pathogonomic for myasthenia, but indicate disturbed neuromuscular transmission. UMLS:C4021045 The variation in the time interval between the two action potentials of the same motor unit is called jitter. This term therefore applies to increased variability in the interval between successive action potentials of the same motor unit, which is measured by electromyography (EMG).