Most believe in order to be strong you have to have tons of muscle and for enough guys I've witnessed doing crazy feats that theory is not necessarily true. Sure muscles look cool and all but if you don't have strong tendons, your muscles won't mean jack shit in situations where muscles won't be enough. The tendons are what hold the whole structure together forming this machine of nerves and bone capacity to move in the best directions possible. Even having flexible tendons make a huge difference in how you move and hold a heavy resistance. Because of training with a sledgehammer, it builds tendons like steel cords (for you marvel fans, think of Vibraniam or Adamantium) and not to mention the increase of testosterone using a heavy resistance through intense exercise.
A favorite hammer of mine is the Thor Hammer that is purely made as if the Norse gods had access to it themselves. You don't have to know Norse Mythology yet the moment you see a hammer of this magnitude, it brings a sense of presence that only a few can ever understand. Picture as if Thor handed you this hammer and you were the chosen few to hone it's power and feel the spirits of Valhalla coursing through your veins and bringing the strength of thunder and lightning into your blood stream the moment you hold it in your hands. It has no equal and it can be used in various areas of training and turning your grip into a structure that is no longer human flesh and bone but that of superhuman machinery of solid matter and the strongest steel that you can imagine. Even the Epic Sledgehammer has that very found affect and if you can handle it, treat it with respect and people will be afraid to shake your hand.
The way I train in using Sledgehammers is by swinging and hitting the tire with such force as possible and for as long as possible. The way I count reps is by taking my deck of cards and do the amount of reps the card requires. I don't also train by the reps themselves, I go after the total amount of weight I have lifted with that hammer for example: If you took a 13.8 lb Thor Hammer and your reps were say 500, you didn't just hit the tire 500 times but you have lifted nearly 7000 pounds total when you mathematically multiply the weight and the amount of reps. That's more than 3 tons, can you say freakish strength? How would that feel to you, being able to handle that much weight and having that amount of strength/endurance? My last workout was with the Epic Sledgehammer and it weighs approx. 39 pounds, that's a lot of hammer; now picture moving that amount of weight in just over 30 min. 600 times. that's over 23,000 pounds being moved, that's over 11 tons. I train by the ton because I don't want to just hit a tire with a heavy object, I want to see how much weight I can move within a period of time that brings out the very pinnacle of strength and conditioning. If you're a strength athlete or an arm wrestler; think how much strength you will acquire doing this type of training in your arsenal. This can aid you winning some big competitions and take down some of the strongest opponents imaginable. Feel the power of the hammer and make your grip the strongest it can be.