You mentioned you are a body builder, I assume you work legs one day & another body part the next day, therefore giving your legs a rest. To build muscle you do tear it down, but then you give it a day or two to repair. I have been out of weight lifting / body building for 20 plus years, but in the day there was theories of only working a body part one time a week. What your doing is aerobic almost, not building muscle, I think aerobic classes are only one hour a day.
Follow what you know for body building, working out a bow muscle is the same, if your pulling a bow or lifting a weight, just the difference between using a machine or free weight.
Dan