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The NutCracker Effect

The Old Top Sheet Hurts – OUCH!!

As the top sheet and blanket (the lever) are often tucked tightly around a thick heavy mattress

(the load), the feet are subject to a “nutcracker effect,”

as they have become a veritable bed sheet fulcrum (the nut).

“Give me a lever long enough and a fulcrum on which to place it and I shall move the world”
(Greek: Ἀρχιμήδης; c. 287 BC – c. 212 BC) 



The tightness at the bottom of the bed is indeed due to the mechanical force of a lever—a second class lever (just like a nutcracker)—as the ‘effort’ is located at one end of the lever and the fulcrum is located at the other end of the lever opposite to the effort. Since the bed is supposed to be so comfortable, the analogy is not readily apparent. But think about it:

  • The lever is actually the sheet. To help you visualize: imagine the sheet was a solid geometric plane of wood connected at the bottom of the bed with a hinge. You would never be willing to put your feet into that wooden crusher. Of course, a bed sheet—unlike a solid geometric plane of wood—has some give; but, down close to where it is tucked in it is surprisingly taut and unyielding. Ah-ha…now you’re beginning to understand the ‘nutcracker effect’!
  • The load is where the sheet is tucked-in under the heavy mattress

  • The fulcrum—or the nut—is your feet. OUCH!!







 The Toes Point Up in the "TV Viewing Position"!


Calf and foot cramping occur in a broad range of the population—from world class athletes, to middle aged people, to pregnant women. The unnatural position of having one’s feet constrained against a taut sheet for a period of time acts as a pseudo binding. This may lead to muscle contractions which can set off a sudden cramp or a spasm. 

Even the Ancient Egyptians wanted their Pharaohs comfortable in the afterlife. 


As our life styles have evolved over the last half century, so too has the role of the bed. The bed has become far more than the province of sleeping and conjugality. With most bedrooms sporting flat-panel TVs and their occupants possessing laptops, smart phones, and tablets etc., the bed is the locus of more entertainment, communication, and commerce than ever before.

Many people prefer to do these activities while under the covers:

  • as a prelude to falling asleep
  • first thing in the morning before officially starting the day
  • if they’re not feeling well
  • when there is a chill in the air
  • if they are wearing little or no clothing and still want to be comfy


The dilemma is that the reclined on the back watching TV, reading, sleeping, or resting position – under taut, tight, tucked-in covers – is not comfortable. The feet are designed to support our body weight; accordingly, they have structural rigidity and prefer to be, more or less, at a 90-degree angle. They are not designed to point for any length of time. Mechanically, the very act of lying on one’s back forces the individual’s feet to naturally maintain their right angle.