At what angle do you hold your MD in front of your body. I know this sounds silly, but I have it stuck out far in front of me (last notch on the adjustment, Fisher F4), and my arm starts hurting in just a few minutes. any suggestions?
Swing your loop just a couple of inches in front of your toes. The closer to straight down your loop is, the less weight on your arm.
Practical demonstration of this concept:
Get two large books about the same weight. Put one in each hand. Hold the left one straight out to your side, and the right one straight down by your side. Wait one minute. See which arm feels like it is going to fall off.