There are perhaps a hundred things that could go wrong with the squat: valgus of the knees, flexion of the lumbar spine, excessive tilting of the pelvis, etc.. As it happens, the practice of strength and conditioning is as dedicated to fixing these problems as it is to improving the movements they plague. Combining certain exercises can have a synergistic effect when it comes to addressing movement deficiencies, making these “combo” exercises extremely useful to have.
One common error with the squat is rotation, whereby the lifter exhibits a turning/twisting of the torso throughout the set. Most of this can be traced back to either poor core strength or a lack of proper bracing. The danger of this is that it predisposes the spine to injury due to the presence of shear stress as well as the displacement of load (barbell).
Location and equipment courtesy of TripleFit
The Pallof press is commonly used as a means to teach and strengthen an individual's ability to generate tension in the core for the purpose of resisting a rotational force. Combining with a squatting movement allows one to to transfer that skill directly over to the other. This movement can be done on either a cable pulley machine or with a resistance band looped around a sturdy post.
Only a light to moderate amount of tension should be used with the Pallof-press-squat; too much will cause the body to cant to one side as a means of providing a counter-weight. Performing these in a similar repetition range as regular Pallof presses seem to work best. Remember: the purpose of this exercise is to build and reinforce proper movement habits, not creating a “burn”. Do not let fatigue mask your ability to execute this exercise correctly, or sacrifice proper form for the sake of getting more repetitions in.
The Pallof-press-squat can be performed both as a warm-up to “remind” yourself how to move, as well as a substitute for your regular core movement. The load you use may be light, but be sure to brace and generate tension just like how you would with a heavy bar on your back or a dumbbell/kettlebell in your hands. Treat it like the actual thing and you will see real results!