The language people reach for while lifting a heavy sofa may serve a practical purpose.

In controlled experiments, participants repeated either a swear word of their choice or a neutral word while performing brief physical tests. Swearing increased grip strength by about 8 percent and power during an intense cycling test by roughly 4.5 percent. Later studies found advantages during push-ups, planks and wall sits.

Researchers first suspected that profanity triggered a surge of fight-or-flight arousal. Heart-rate measurements provided little evidence for that explanation. More recent research points instead to disinhibition. Breaking a small social taboo may reduce restraint, increase confidence and help people commit more fully to an uncomfortable effort. 

Swearing can also increase pain tolerance.

The effect is a temporary performance boost rather than newly acquired muscle. A strategically deployed expletive appears to help the body use a little more of the strength it already possesses.

It may not move the sofa by itself, but it can improve negotiations between the muscles and management.