That's why I've pretty much given up canvas. I just can't deal with the weight through the machine. My left shoulder is almost back to normal but the rotator cuff is pretty delicate. I find that if I hold a coffee mug (empty) at my left side, then try to lift it to shoulder height - straight out to the side in line with my body - I can sometimes get it up there, sometimes not. Kills me because I've always been very strong for my size and height. Sucks getting old.
Anyway, have your wife photo/video you at your machine sewing. Look for faults in your posture and motions. You maybe doing this to yourself a bit. I was, simply by having my seat too low. My left shoulder was hunched up higher than my colllar bone, aggravating the problem. I also was using my left elbow to hold/push canvas through the machine. I'd bind the fabric to the table with the elbow and hold or push. Be very conscious of your position and motions. You probably ARE now that you're in pain.
June
Anyway, have your wife photo/video you at your machine sewing. Look for faults in your posture and motions. You maybe doing this to yourself a bit. I was, simply by having my seat too low. My left shoulder was hunched up higher than my colllar bone, aggravating the problem. I also was using my left elbow to hold/push canvas through the machine. I'd bind the fabric to the table with the elbow and hold or push. Be very conscious of your position and motions. You probably ARE now that you're in pain.
June