Train for the flexed-arm hang directly by testing your maximum hang time. Approximately three times per week, perform sets using 75 percent of that time. Do five to seven repetitions and rest two minutes between each hold. Each consecutive week, hold your flexed-arm hang two to four seconds longer and decrease the rest time by five to 10 seconds. Do these flexed-arm hang exercises on the same day, but before, you weight train.
Perform weight-training exercises that strengthen your back and biceps muscles. Execute lat pulldowns using a pulldown machine, single-arm dumbbell rows, 45-degree bent-over barbell rows and dumbbell biceps curls. Do three sets of 15 to 25 repetitions with weights that are about 65 percent of your one-repetition maximum -- the most weight you can do an exercise in one repetition. Rest 30 to 60 seconds between sets. Aim for two or three training days per week with these exercises, and leave at least 48 hours between those training days.
Perfect your form. When you hold the flexed-arm hang, focus on keeping your hands just one fist-width apart and the elbows pulled back. Pull your core muscles in tightly to support your lower back. You may also find bending your knees slightly, but not allowing them to reach higher than your waist, helps you hold longer.