The latissimus dorsi muscle is critical for overall back form and appearance. It covers all of the middle and much of the lower parts of the back. Seated rowing not only activates the latissimus dorsi, but also the teres major, trapezius, the short head and long head of the biceps brachii and the biceps brachialis muscles. Therefore, the seated rowing not only hits the muscles in the middle and lower back, but also some muscles in the shoulders and arms.
1) Sit in the seated rowing machine unit, and adjust the seat height so that the torso support contacts the chest at about mid-sternum level. This will help to brace your upper body and prevent excessive movement in your lower back. The chest brace should also be placed out far enough so that when you are in the machine, you can just reach the handles. This will ensure that you are able to get a good range of motion at the bottom of the exercise.
2) Brace your feet on the foot supports, slightly arch your back, and in-hale as you pull your hands and arms backward. Concentrate on squeezing your scapula together as the elbows are pulled backward. This will help to activate the muscles along the spine, including the trapezius muscles.
3) The elbows should point directly backward as you are pulling the handles backward. Continue pulling the handles until your hands are at about midway point in your lower ribs.
4) Slowly lower the weight and let your elbows extend and straighten your arms. Resist the weight on the way down, and do not let it drop in an uncontrolled fashion. Exhale as the weight is being lowered. Hold the bottom position for a count of two. This will stretch the middle-back musculature between each contraction. Continue to the next rep.
Make sure you control the weight. The speed of the movement should also be relatively slow on the way down. It will do you no good to lift a heavy weight by jerking it up by using momentum, and lifting away from the torso pad (because this could hurt your lower back), and letting to drop the floor in an uncontrolled fashion. You should always make the effort to try slow the weight on the downward part of the lift, as this eccentric part of the contraction is as important as the lift upward. It is also important to get your elbows back as far as possible in each rep. A complete range of motion in seated rowing is critical to ensure complete activation of the entire back musculature.