Whether you're working up to your first real pull-up or cranking them out in sets of 10, few back exercises are more efficient. Pull-ups target all your major back and pulling arm muscles at once, and, because they work so many muscles together, they're excellent preparation for everyday movements that demand the same coordination. That said, doing pull-ups every day is too much of a good thing; you should give your muscles at least 48 hours of rest between workouts.
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Give Your Muscles a Rest
The trauma that strength-training exercises such as pull-ups cause to your muscle fibers triggers satellite cells to rebuild the muscle. So it's not actually the pull-ups that strengthen you; it's the repair process that takes place afterward. A rest period of at least 48 hours gives your body time to complete the repair process, leaving you a little stronger and better prepared for the next round of exercise.
More Isn't Always Better
Light exercise can help you manage mild muscle soreness, but if your muscles are still very sore 48 hours after your last round of pull-ups, a longer rest is in order. If severe soreness continues, you've either hurt yourself or overdone the last workout. It's time to scale back your workouts and, if the soreness does not resolve quickly, consult a medical professional to diagnose and treat any injuries you've incurred.