These point are very confuse in the actual and past sport.It is not well defined "back squat". For example, 20 cms of difference in the place of the bar, make it a "neck exercise" or a "leg exercise". Anatomys are very different, so risks of injuries and individual perception of exercise.Objectives and lifes of the athletes are different.The logica employed is not strictly, is a "fuzzy logica". Examples and more examples, opinions, but not much scientific and rigourous information. In the discurses are confused the concepts of "necessary" and "sufficient". And not well defined "convenient".A experimental design implies control of several variables, sofisticated sampling and statistical treatment of data.I think these opinion -in both senses - as conjectures, legitim, valid, but conjectures, referencies, not absolutes trues. A basis for experiment and for investigate.