Like eric said chinups(palms towards) hits more biceps, if you want to really hit your lats and back, do pull ups. Fairly wide grip head looking down and legs somewhat back... If you lean to far away with your shoulders(move your elbows forward) you over compensate with your bis'... Head down, bring your elbows straight down to your sides. Get the form down on pull ups and you'll be happy with the results.... One of the best back exercises.... IMO

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You come into the world weak, and you will leave the world weak. What you do in between is up to you!