Meat and fish steam in 3-10 minutes, depending on the size and thickness of the food. Since steaming occurs at 212°F/100°C and a good poaching temperature is 140°F-170°F, it takes less time to steam meat than it does to poach it.
Additionally, overcooking meat, even meat that comes from the more tender muscles, can make it tough. That's because heat causes the proteins in the meat to firm up. Overcooking also basically squeezes the moisture out of the meat, making it dry as well as tough.