physiologic tremor physiologic tremor physiologic tremor is a tremor or trembling of a limb or other body part. the recorded frequency is in the range of 8-12hz. 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. physiologic tremordifferential diagnosishyperthyroidism