To get the most out of your arm workouts, remember the following points:
Do not lock your elbows. When you lock your elbows it causes the wrists and shoulders to lock too. Hyperextending the arms, especially while lifting weight (including body weight), increases the risk of injury. To get the most benefit when performing arm exercises use your elbows’ full range of motion, but without forcing your arms into a locked position.
Pay attention to exercise form. It’s common for shoulders to slump forward or hunch up towards the ears. This puts the shoulders in a vulnerable position when lifting weights. To prevent poor posture make sure your chest and shoulders are open. To help with this, every few moves shrug your shoulders downward and roll them back to reset your form.
Choose the right weight. Choose a weight that allows you maintain proper form but is heavy enough to challenge you. For example, if you are performing 8 to 12 reps of an arm exercise, the last two reps in each set should be difficult to finish, while still maintaining good form. However, if you start using other muscles to help lift the weight, use momentum, or otherwise change your form choose a lighter weight.