@boomerang,
When i was at university, i took phys ed courses for the interest--swimming, weight lifting--things which required equipment or facilities which i would not otherwise have access to. One class, which i enjoyed but had to drop (too heavy a load that semester) was fencing. The instructor told us that the biggest problem for people new to the sport was fatigue in the sword arm. By the end of the course, one was supposed to be able to hold a sabre (a very heavy sword) at arm's length for 15 minutes. He then told us that we do different things with our hands, arms, feet and legs. So, first we held the sabre out at arm's length in the "off hand." We were to hold it for 5 minutes. People's arms were trembling and they were moaning and groaning, but everyone held the sabre at arm's length for 5 minutes. Then we switched to the dominant hand. Nobody made it past two minutes, and most people didn't last that long. He told us we use a different set of muscles and different types of muscles for the tasks we expect of our dominant hands and our "off" hands.