At its base there is a great working principle that can be beneficial even to natural bodybuilders, namely — training of opposing muscle groups. (fitnessandpower.com)
By combining these three exercises you can exercise the two opposing muscles in the core of the body at the front and the back. (mystrengthtraining.com)
They simultaneously work opposing muscle groups, don't necessarily require the use of specialized equipment and are simply one of the most effective exercises for building upper body mass and strength. (fitnessandpower.com)