Yellowbird

I'm curious as to how you train your shoulders for carrying a boat? I have little problem carrying a 70+ pound pack for days on end in the mountains (as long as I have my one alleve tablet per day :) ) but slap a 55 lb Bell northwoods on my shoulders and I'm hurtin at about 1/2 mile. What a wimp ;). Maybe it's the thin hard closed cell foam that my buddy insists on using, (ya think that might have something to do with it ;D)

Anyway, just curious as to what people do to train shoulders to carry a boat. I didn't know there was such a thing.