The chin-up is one of the best exercises you can do for strength and muscle building. This is a compound exercise that works every muscle on you upper body. It primarily targets the lats and biceps, and it also works the rhomboids, traps, chest, shoulders, triceps and forearms. Your core, abs and lower back will also assist as stabilizers.
Since chin-ups work so many muscles at once, they will help you build much more muscle than by doing many smaller movements combined, this is great for people who don't have a lot of time to exercise. The chin-ups will also improve your posture, making you look much better. This is especially important if you have a desk job. Just a few chin-ups a day can help you correct back problems caused by sitting slouched for extended time.
Chin-ups are a great test of strength and fitness. But they are also very hard to perform. If you have never done them before, most likely you won't be able to do even one. Don't get discouraged though, the chin-up is very important to learn because it has so many benefits. Try an easier variation like the cable lat pulldown or assisted pull ups to work your strength up to the point you will be able to do a complete bodyweight chin-up.
The chin-up is a variation of the pull up. The difference between the two moves is that with the chin up you position your hands with a underhand grip (palms facing your body). While with the pull up, you use a overhand grip (palms facing forward). The change in hand position affects what muscles are worked most. Both variations work the lats in a similar way, but the chin-up allows greater involvement of the biceps and and the chest to assist the motion, while the pull ups isolate the back muscles more. So for most people chin-ups will be easier to perform.
Keep your form strict rather than utilizing momentum to power yourself over the bar. Doing chin-ups with a leg whip, and a jerking motion might feel easier and allow you to do more reps, but it will not train the proper muscles and will decrease your strength gains. It will also increase the risk of injury.
Focus on pulling your elbows, not your hands. As with any pulling exercise that you perform for your back, you should always focus on pulling the resistance using your elbows. This simple trick will help you keep the pressure where you want it, on your lats, while minimizing the stress on your arms. Imagine your hands and forearms are merely hooks that attach you to the bar. Instead of thinking about pulling your body upwards towards the bar, focus on driving your elbows down toward the floor instead.
Don't place the hands too wide. The hands should be positioned shoulder width apart or narrower. Having a wider grip will not result in wider lats, but might cause shoulder damage.
Use the full range of motion. It is important to remember that the chin-ups are a back exercise. Doing partial reps doesn't allow your lats to work properly which encourages the arms to do most of the work. Finish the reps with arms almost straight but not locked at the bottom, and your chin over the bar at the top.
Don't let your elbows flare too forward. Try to keep the elbows under the bar, and focus on driving them towards your back. This will keep the pressure on your lats instead of the biceps, and will keep you in a better mechanical position making it easier to pull the chest up.
Keep your body slightly tilted backwards. In order to perform a good chin-up the shoulders need to be retracted and set to engage the posterior muscles. To hit your back properly during chin-ups, think of raising the rib cage toward the bar, and arch the back a little.