Is yawning a sign of high blood pressure

Athletes do it before competition. Concert violinists do it before going onstage. Paratroopers even do it before throwing themselves out of a plane for the first time.

What is excessive yawning a sign of

Of all the involuntary physical reflexes humans experience before stressful events, yawning seems not only improbable, but also kind of ridiculous—like sneezing a lot before a knife fight.

Most of us (rightly) associate these 3 to 6-second oscitations with sleepiness and boredom---not feats of daring and skill.

According to Robert Provine, a University of Maryland, Baltimore County, neuroscientist and author of Curious Behavior: Yawning, Laughing, Hiccupping, and Beyond, we really do yawn most when we're tired. "Right after waking and before bedtime," he says, "which is consistent with yawning's role in facilitating state changes: sleep to wakefulness, wakefulness to sleep, arousal to de-arousal, or vice versa."

But yawning does more than just engender physiological state changes.

Human fetuses begin yawning in the womb after about 20 weeks; dogs frequently yawn when asked to do t

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