I'm new to archery , and from what I've been watching you supposedly squeeze your back muscles together to pull the bow back. I'm a finger shooter so it's different than with a release. I just use my arm and pull hard with my arm.
You may feel as though you are using your arm muscles to draw the bow, but I assure you that unless your DW is under10lbs you are using back muscles to draw the bow. One way to understand this is simply isolating your back (stand with back straight against a wall) and try moving 20/30/40/50/60/70lbs around with only your arms - my guess is there are very few that can manage. I consider myself quite strong and big build (210lbs) and I can only manage about 40-50lbs of "arm only" weight with a struggle - 20-30lbs would be more comfortable and 10-20 for long term reps.
It is difficult to learn the proper way on your own. I recommend you try and find a coach in your area and take a few lessons. Fingers does make a difference, just think of all the Olympic style recurve shooters.
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