Originally posted by heavenhell:
Different movement pattern, different primary muscles involved.
x 2. you need to work specific to improve on specific areas.
for push ups, the agonist are your triceps and antagonist are your biceps. meaning, you will feel more strain on your triceps than your biceps and naturally you are training your triceps more.
if you want to improve chin up, the exercise you carry out should be as close to the movement of chin up as possible. my suggestion, if you can do a few chin ups, you should heed the advice of the first reply. otherwise, you can head down to the gym to use the assisted chin up or lats pull down machines.
before you start get some knowledge whether to train for strength or endurance too!
hope this helps.