Physiologic tremor

Physiologic tremor is a tremor or trembling of a limb or other body part. The usual frequency is about 10 times per second. It occurs in normal individuals, especially when they are stressed by anxiety or fatigue. It is therefore common in sports such as rock-climbing where it is known by names such as Elvis leg or sewing machine leg. It may occur in an enhanced form as a pathological symptom of conditions such as hyperthyroidism or stimulants such as caffeine.