New research suggests that being weak with laughter is no joke -- laughing actually causes changes that make our muscles go limp. The researchers studied the effects of laughter on muscle tone by examining the activity of a simple neurologic pathway, known as the H-reflex, which causes a contraction in one of the calf muscles when a nerve in the shin area is stimulated electrically.

When four study volunteers laughed aloud in response to funny pictures or jokes, this reflex virtually disappeared, and muscle contraction in response to the stimulus fell dramatically. But smiling had no such effect. The researchers are not sure exactly why this occurs, but they suspect that other strong emotions including anger or fear may cause similar changes in nerve circuits, with resulting muscle weakness.

Lancet  September 4, 1999;354:838

Dr. Mercola's Comment:

Emotions have very powerful influences on the body. This is an interesting observation that tends to support some of the work I had presented previously regarding the energetic connections of the emotions to a person’s physiology.