Pull-ups measure your relative strength, which is an indicator of how strong you are in relation to your body size. According to Jason Hartman, U.S. Olympic Committee Strength and Conditioning Coordinator, there is no better exercise to develop upper-back strength and size. "Pull ups are a necessity for any program with the goal of increasing size and strength of the upper back," Hartman explains. Trainers commonly use pull-ups to assess an athlete's upper-body strength. The three exercises that will help you improve your pull-ups and relative strength quickly are negative pull-ups, assisted pull-ups and inverted rows.
Lowering Down: Negative Pull-Ups
Negative pull-ups can effectively increase your strength, ultimately leading to an improved number of pull-ups. Either have a training partner spot you or use a bench for assistance to get pulled into position with your chin above the bar. Keep your chest up and focus on tightening your lats before taking your feet off the bench. Hold this position for as long as possible before slowly lowering into the hang position. Once you've fully descended, the repetition is done. Repeat this exercise until you're too fatigued to hold the top position and/or lower in control.
Moving Up: Assisted Pull-Ups
Choose one of three props to help you perform an assisted pull-up -- an exercise band, an assisted pull-up machine or manual assistance from a training partner. You can do a larger quantity of pull-ups with assistance, which will eventually increase your strength and ability to perform a greater number of pull-ups without assistance.
If you're using an exercise band, loop it over the pull-up bar and place one foot into the hanging loop. Straighten your leg. Tension created by lengthening the band will unload body weight and provide assistance while doing pull-ups. In an article appearing in "Men's Fitness," performance-enhancement coach Jason Ferruggia recommends that you switch to lighter bands until you can do a few reps without a band.
Many gyms have an assisted pull-up machine. Follow the machine instructions for set-up and select your desired weight. The greater the weight you choose, the greater the assistance.
If you choose to have a training partner assist you, ask him to place his hands at the base of your lats and aid you to as you pull up.
A Different Angle: Inverted Rows
Set a barbell in the power rack at waist height. Lie under the barbell and grip it at the same width as you would for a pull-up. Hang beneath the bar with your legs straight and your feet propped up on stable bench at about the same height as the bar. Don't let your hips sag; activate your core and hip extensors. Pull your chest up to the bar and lower. Repeat until you cannot maintain solid technique and/or cannot bring your chest to the bar again.
What About Lat Pulldowns?
Lat pulldowns may also help you increase your pull-up strength, but this exercise is not as effective at training to improve at pull-ups as negative pull-ups, assisted pull-ups or inverted rows. When you perform a pull-up, you exert force on a fixed object and pull your body through space, making it a closed-chain exercise. In performing a lat pulldown, you move an object instead of your body, making it an open-chain exercise.