The frequency with which you train your back depends on your goals and your conditioning level. For general health and fitness, one or two times a week; for powerlifting, train your back twice a week. If you compete in weightlifting, your back will get trained to some degree every time you go to the gym. As an athlete, your training will be based upon your specific goals at the time. Your training intensity and volume also play a role in how quickly you can recover from your training.
Twice Weekly for General Fitness
If your goal is simply to develop a better physique, train your back twice a week with three days of rest between each training session. During your first workout, perform chin-ups, barbell or dumbbell rows, and hyperextensions for multiple high-repetition sets. Three to five sets of 10 to 15 repetitions per set helps build muscle and improves your tolerance for training volume. Three days later start your back workout with deadlifts but perform no more than three sets of five repetitions. Three sets of pullups and rows for five to eight repetitions each completes this higher-intensity workout. Rest for four days.
Powerlifters: Once or Twice a Week
If you compete in powerlifting you will train your back once or twice a week, depending on your program. If you bench twice a week, work your upper back with chin-ups and rows on these days. If you train three times per week, all of your back work needs to follow your deadlift training. Your total training volume is determined by your conditioning level and how close you are to a meet. If you are only a week or two out from competition, you may wish to drop some of your back work to allow yourself to recover.
Weightlifters Do Enough Already
The sport of weightlifting involves competing in the snatch and clean and jerk. Both exercises are highly technical, involve getting as much weight as you can over your head, and recruit your back. Your spinal erectors and your trapezius -- the muscles of the lower and upper back -- work hard during these lifts. The wide muscles of your back, the latissimus dorsi, contract to stabilize you during each lift. Some weightlifters do little to no extra back work, others do a few sets of rows at the end of one or two works just to focus directly on the latissimus dorsi, with barbell rows being the exercise of choice.
And If Your Goal Is Conditioning ...
If your goal is conditioning, train your entire body every workout. You should be training three times a week with one rest day between training sessions. You should work your back every training session. A few sets of chin-ups and rows following your squatting will work your back. If you train this often, avoid deadlifting, as you will not be able to recover before your next training session. If you wish to include deadlifts, do so on your last workout of the week where you can rest two days prior to training again. Limit your deadlifting to only a single set of five to eight reps.