Its Scott again. We last saw him holding his plank. Here he is now performing a seated row. To engage the back muscles well, the upper back must arch backwards. Keep the shoulders down low and squeeze your armpits. So pull the low abs in and keep the low back stable. It will be tempting to stick the tummy out instead of arching the upper back. This will put too much arch in the low back and may cause back ache.
I actually dislike the seated row. The exercise does work the lats, the big muscle that runs from the arms to the bottom. But it also engages some troublesome muscles called the rhomboids. If shoulders are in good condition, this is a good thing. However, lifestyle means most people’s shoulders are not as good as they should be. Rhomboids rotate the shoulder blades upwards. Also lifestyle means many people lack the ability to bend their upper back backwards enough to properly engage the back muscles. However, done well, it is a good exercise.