Pullups and chinups are performed using a fixed, elevated bar, and both exercises are good for building strength in your hands, forearms, upper arms, shoulders, back and abdominals. They are intense exercises, so to improve your performance, do fewer repetitions more often, rather than a high number of repetitions less frequently.
Pullups Vs. Chinups
While both exercises work similar parts of your body, there is one subtle difference. Pullups are performed with your hands wrapped over the bar and your palms facing away from you. The grip for chinups is with your palms facing toward you, or facing in toward each other, which makes them slightly easier to perform.
To assess the optimum number of repetitions for your ability, perform as many pullups or chinups as you can in a single set, while still maintaining your form. This will give you the ideal number of reps per set that you should begin with. When you're just starting out, aim to do around 60 reps a week, taking as many sessions as you need to complete them. Regular workouts with fewer reps will build your strength quicker than less frequent sessions of higher reps.
Once you can comfortably do 60 repetitions a week, increase the number, and continue to do so every time you notice your strength improving. You can also measure your improvement by going back to the original test -- doing as many reps in a single set as you can. You should be able to do more than you could the first time.
Maintaining Your Form
Throughout your pullup and chinup training program, maintain proper form. Start a pullup by gripping the bar with your palms facing away from you and your hands slightly wider than shoulder-width apart. Hang from the bar with straight arms, then pull yourself up slowly so you use only the strength in your torso, rather than momentum.
To do a chinup, start with the easiest grip, palms facing you, and hang from the bar with your arms extended. Use your back and shoulder muscles to pull you up, keeping your elbows tucked into your sides as you bend them. Once your chin has passed the height of the bar, inhale and slowly lower your body back down to the starting position before doing another rep. Your torso and legs should remain in line throughout each chinup.