Knickerbocker's theory does not explain why the first firm in an oligopoly decides to undertake FDI rather than to export or license. (Hills, 2008) also suggested that the imitative theory does not address the issue of whether FDI is more efficient than exporting or licensing for expanding abroad.
Isometrically, the lower back, the upper back, the abdominals, the trunk muscles, the costal muscles, and the shoulders and arms are all essential to the exercise and thus are trained when squatting with the proper form.
1 If you do air squats right, not only do air squats engage your legs and butt muscles, they also work your core, back and shoulders.  They increase mobility. To be able to squat properly, you need basic hip, ankle, and torso control.