People commit the cardinal sin of grunting at the gym (just ask Terry Crews) because it appears to be a natural occurrence of inhaling deeply, breath holding, and then exhaling. I would guess some might have an ulterior motive, like being noticed, or in a competitive situation to intimidate a fellow lifter or opponent.
In the past it has been suggested that inhaling deeply, holding one’s breath while straining, and then exhaling was an appropriate method of generating great force. In fact, data suggests that the “fluid-ball” created by this process protects the spine from injury. There has been recent concern for this technique in that breath holding can lead to higher systolic, diastolic, and mean arterial pressures as well as cause a decrease in middle cerebral artery pressure. A decrease in middle cerebral artery pressure could lead to “weight-lifter’s blackout.” Thus, most resources suggest a minimal amount of breath holding or Valsalva maneuver during straining maneuvers.
Vocalising during a maximal muscular effort appears to be a positive influence on improving performance.
Early studies show that “shouting” during grip strength increased force by 7.4%. Our early work on grunting during an isometric dead-lift demonstrated 1%, 2%, and 5% increases in power-lifters, American university football players, and a graduate student control group, respectively. These beneficial changes were “competitively” but not statistically significant. Even vocalising the “Kiap” during karate has been shown to increase strength. More recently, our research with tennis players has demonstrated statistically significant increases in forehand and serve velocities (4.5 mph) of university tennis players, regardless of gender, grunting experience, or like or dislike of grunting. Thus, vocalization appears to increase force and velocity.
So having established that grunting does actually have a positive effect on exercise performance the next key question is whether or not the volume of the grunt can be lowered while still achieving the same results. The short answer is yes. We will present data at the American Physical Therapy Meeting in Indianapolis in February 2015 that will demonstrate no difference in isometric tennis forehand forces when subjects grunted (noisy) or performed a more quiescent form of exhalation. Our findings suggest that benefits of a more aesthetically pleasing quiescent exhalation may be used and can replace grunting yielding similar benefits.
