legs, back, chest, shoulders, arms. And within legs you would prioritize multiple joints exercises like squats before leg extension. And with the chest you would chest press (higher intensity, more exhausting) before doing the flies. And with the back you would want to do a bent over row, which is done using ‘free weights’ like the barbell, and is of higher intensity, before doing a seated row. Use of machines reduces the intensity (and so the exhaustion) even if the muscle group employed is the same as in the example of bent over row and seated row.
