Im part of another forum & a guy recently posted a piece on this, ill quote some of what he said, see what you think. "First off Lets look at the latisimuss dorsi themselves. Most bodybuilders fail to completely develop lats more often than not, this occurs due to wrong hand spacing and grip. One common mistake is using wide grip on lat pull downs and chin ups. Bodybuilders believe that a wider hand spacing provides more stretch, greater range of motion and that it will bring out BACK THICKNESS. But 1. you cant change the shape of a muscle and 2. the only place the lats have to grow is outwards... nowhere else. But the truth is opposite A wide grip provides LESS stretch for lats than you'd get with a narrow grip. Furthermore the wide grip actually PREVENTS greater range of motion by allowing the upper arms less rotation at the shoulder joints. Now lets look at grip. Your biceps are strongest when your hands are supinated. since biceps primary action is supination of the forearm and NOT elbow flexion..just yet. supination THEN flexion. Yet most bbers work their lats with their hands pronated turned away from them - which puts them at their weakest. Since biceps are more important supporting muscle for lats, you'll be able to work your lats harder if you use a supinated grip when you do chin ups. Understanding the specific actions of muscles is most important and a vital step towards efficient bodybuilding. You should be looking to make exercises easier instead of harder, thus being more productive using more weight. Lastly as for stretch.. you can see it yourself. : Put your hands up in the air wider than shoulder width...or wider if you like.... and stretch your arms out as far as you can... see..not much stretch.. now put them well above your head as far as you can..... just like the da vinci drawing with the man in the circle.. put them together above your head and now stretch.... see. so for optimal lat stretching you should hold one hand on the wall further towards the other arm...and tilt your pelvis up from the OPPOSITE side that you want to stretch. CONCLUSION: To work lats optimally, do pull ups with underhand shoulder width grip...and INITIATE MOVEMENT from your shoulder joint. move your lats and not your arms... so your chest should almost touch the bar. ARCH your back as much as you can when dpoing pull ups since lats are also inserted at the pelvis (iliac crest), exhale on the way up. "