Hysterical strength is a display of extreme strength by humans, beyond what is believed to be normal, usually occurring when people are in life-and-death situations. The classic anecdotal example is of parents lifting vehicles to rescue their trapped children. The extra strength is commonly attributed to increased adrenaline production, though supporting evidence is scarce, and inconclusive when available. Research into the phenomenon is difficult, though it may be possible as adrenaline is known to affect muscle twitch and endurance.