We know that swearing increases pain tolerance. That has even been backed up by research, and now new research shows it can also increase strength and power.
Repeating a swear word was compared to repeating a neutral word during two different experiments. In the first, subjects completed a Wingate anaerobic power test. In the second, subjects completed an isometric handgrip test.
Greater performance was achieved in the swearing conditions versus the non-swearing conditions for both the anaerobic power test and the grip strength test.
Swearing is effective at increasing pain tolerance, isometric strength, and bicycle wattage. However, in the current study, autonomic arousal seemed not to be the cause. One researcher said, "Swearing seems to be a form of emotional language."
Maybe it's the emotion behind the words that allows the increase in performance. Whatever the reason, maybe you should start cussing during training. If it increases strength and power, why the hell not?