Anyone who has ever slung a sledge hammer knows what a workout that is for your upper body, but sledge hammers should not be restricted to a construction site. Although swinging one around your gym probably isn't safe or allowed, you can exercise with a sledge hammer or outside as you would with free weights such as kettlebells and unilaterally loaded dumbbells.
The overhead swing is an all-over upper body toner. Overhead strikes work your arms, shoulders, back and chest. This exercise challenges your muscular endurance as you continually swing the sledgehammer, switching sides to get an even workout. To perform the overhead strikes, take the sledge hammer outdoors and put a tire on the ground in front of you. Grab the sledge hammer with your left hand on the bottom and your right hand near the hammer at a comfortable distance apart. There is no exact best distance, just what feels right. Raise the sledge hammer above your head and over your right shoulder, and then bring it down toward the center of the tire. The body twists back toward the right as you raise the hammer and twists forward again as you strike down. This motion is similar to chopping wood. Switch sides after 10 reps. Perform the exercise for the desired amount of time.
The Russian twist is a classic core exercise that you can do with a dumbbell, medicine ball or lying on an exercise ball. You can also do this cradling a sledge hammer. The Russian twist targets your abdominals. To perform the Russian twist, sit on the floor and hold a sledge hammer horizontally in front of your chest with your elbows bent. Bend your knees and place your feet flat on the floor. There needs to be room for the sledge hammer to move without bumping your legs. Next, lean back slightly with a straight spine. Twist to the right and then return to center. Then, twist to the left. Returning to center between each rep keeps momentum from taking over. This also gives your abs the additional challenge of stabilizing your spine isometrically. Turn the sledge hammer over after you complete half of the desired number of reps. The disproportion of the weight due to the hammer being on one side makes your core work harder to stabilize your body.
The seated pronation exercise is typically done with a unilateral dumbbell. A unilateral dumbbell has a weighted plate only on one side. Performing this exercise with a sledge hammer is more challenging though because of the longer length of the handle. This is ideal for people looking for large increases in forearm strength. To perform this exercise, stand holding the sledge hammer with your right hand, grabbing close to the hammer end. Bend your elbow to 90 degrees and hold your arm at your side with your elbow at shoulder level. Start with the sledge hammer vertical with the handle pointing to the floor. Then, turn your hand inward until the handle points almost toward the ceiling. This is pronation, which means turning the palm face down. Return to the starting position. Perform the desired number of reps and then repeat with the left hand.