When it comes to body-weight exercises, they don't come much tougher than the wide-grip pullup. Even if you're a competent chin-up master, you'll find the wide-grip much more taxing. This can be a good thing, though, as switching to a wider hand spacing recruits different muscles and gives your training new purpose.
The lats are the winglike muscles that run up your side from your hip bone to your armpit. While any pullup or chin-up variation hits your lats to a degree, going wider is more effective for lat development. Pullups are also performed with an overhand grip, as opposed to an underhand grip as used for chin-ups, and this makes a difference, too. According to Brad Longazel of the Complete Performance Institute in Kentucky, wide overhand pulls activate the lats more than wide or narrow underhand pulls.
Retracting for the Rhomboids
If you think of the pullup as just an up-and-down movement, you're selling yourself short. To work the rhomboids -- the muscles in the middle of your upper back -- retract your shoulder blades as you reach the top of the movement. For this move, sometimes referred to as the sternum pullup, strength coach Jon-Erik Kawamoto recommends bringing your sternum to the bar, pulling your shoulder blades back and pushing your chest out to maintain tension on the rhomboids.
Go Fat for Forearms
Holding all of your body weight throughout a set of wide-grip pullups requires tremendous grip strength, which puts strain on your forearm muscles. Take this forearm and grip aspect a step further by increasing the thickness of your pullup bar. Strength coach Charles Poliquin advises wrapping tape around your bar or using specialized rubber fat grips to increase its diameter.
Perhaps surprisingly, wide-grip pullups work your core muscles, too. Your midsection doesn't actually move during the pullup, but Boston-based trainer Eric Cressey notes on his website that you need good anterior core control to perform pullups and that the lats play a major role in developing core strength. So if you're building your lats, you're strengthening your core at the same time. Due to their increased difficulty over narrow-grip chin-ups, you'll have to work harder to maintain balance and stability when doing wide-grip pullups, so your core will get a much tougher workout.