You could try using an anti-inflammatory cream, something containing a heating element, and massage it really well into your hands, fingers and wrist before you start sewing, then repeat it through out the day. It will help loosen up the tissues and tendons in your hands and warm them up prior to using them.
Like doing warm-up stretches before competing in sports events. If you can't use a cream just try massaging each hand really vigorously until you generate heat from them.
When you come home at night, soak them in a cooling ice-bath, 5 minutes in, 5 minutes out, for about 20 minutes, then repeat it before you go to bed and try not to use them for anything that requires, gripping or clasping.
Rest them up for the next day.
Hope this helps, hugs n roses, Meganne
Devon, Are you using the leather needles? They actually cut a hole as they sew and make the sewing much easier. I made some leather curtains once. What a job they were! Can you make your project simpler in any way to cut down the sewing time?
Also, make sure the pressure foot is on the highest setting so you aren't fighting that too. Is there any way you can cut down on how many hours you are doing this sewing? There is only so much you wrists can handle. Are you wearing the heavy-duty wrist braces with the steal supports. You can permanently damage them, and you would have to file it as a workplace injury and get compensation for it. It's not worth having permanent damage to your joints.
When I sewed on leather I did use the teflon foot and put a piece of tissue paper (cut strips) on top and the bottom. Made the stitch length longer. It's heavier than fabric and if you can extend your work surface that will help support the weight of the leather. My DH came to my rescue a few times and helped hold while I sewed. At the time I was sewing the leather I only had a denim needle that broke a few times and used tape instead of pins.
DeVon, I am so sorry to hear that you wrist are hurting - use some hot & cold packs on them - tonight - might help for tomorrow's work. *4U