It's actually multiple muscles, and the myth may have emerged because you've probably never felt your tongue get tired. Even still, it isn't the strongest muscle system. The honor of strongest single muscle likely belongs to the masseter, in your jaw. From Scientific American:
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By sticking a pliable air-filled bulb into a subject’s mouth, scientists can measure the maximal pressure the tongue can exert on an object. This device, called an Iowa oral performance instrument, is placed on the tongue and subjects are asked to push it toward the roofs of their mouths as hard as they can. Scientists also use this bulb to measure endurance, or how long the tongue can hold a certain posture.
It is no secret that spacesuits are heavy. The full spacesuit worn on the space shuttle, including life support system, clocked in at 310 pounds. At the same time, these suits are bulky, and hard to move around in. So researchers are looking for alternatives—skinnier suits that would weigh less, be more maneuverable, and maybe even have the bonus of helping to support the muscles and skeletal system, which can take a beating during prolonged periods of weightlessness.
Txchnologist has a story up right now about the quest for a better spacesuit. It includes a in-depth look at the BioSuit, which Pesco wrote about here back in 2007. But there are other approaches being explored, as well.
One concept I found particularly interesting might not do much to solve the bulk issue, but could make a big difference for astronaut muscle tone.
In this case, the engineers hope to retain astronauts’ muscle and bone strength by affixing cell phone-size gyroscopes to their arms and legs to imitate gravity. “The property of these control-moment gyroscopes is that they resist changes in angular momentum and thus could apply a couple of pounds of force (torque, in reality),” [researcher Kevin Duda] says.
With a pair of the rechargeable battery-powered units on each appendage—forearms, upper arms, calves and thighs—the astronauts would feel resistance to motion that would to some degree simulate that of normal gravitational force. When floating in deep space or near asteroids, the gyroscopic units, perhaps installed in backpacks, could help astronauts to stabilize their attitude so as to “maintain orientation toward the task at hand to boost operational efficiency.”
The last space suit on the Moon
The seamstresses behind NASA's space suit
Spacesuit adjusts for gravity, or lack thereof
Download 1st chapter of book about the spacesuit's history
Interview with space suit designer
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