When we row with relaxed shoulders and arms, hanging on the handle as the legs do the work, we are using the lattisimus dorsi muscles (the 'lats'), a wide swath of muscles that connect under the arm pit from the upper arm across the middle to lower back.
If you do pull-ups like you row, you can get your body moving largely using the lats. It is not just an arm exercise.
As you row, over time you will discover that your back will strengthen, in part as a result of the response of the lats to their use in every stroke. This strength is a good thing, helping the body to maintain good posture and giving it support for daily activities.
Since you use the lats, consider stretching the lats. A set of a dozen lats stretches is in the works. In the meantime, try these:
- Lie on your back, knees bent and feet flat on the ground. Hold the arms straight up from the shoulders. Set the lower back against the floor. And slowly bring the arms, holding them straight, in an arc over your head back to the floor so that they are in line with your back (the 'above your head' position, but you are prone).
- Squat down comfortably and hold onto a weight machine or door frame or something else that will support your weight (could even be an exercise partner doing this in mirror image). Holding on with arms straight out in front of you, let your body settle backwards and feel the lats stretch.
- Stand up straight and raise your arms over your head.
- Hold onto a chin-up bar and hang.
You will like the way these feel.