One of the first questions a person asks when their gains begin to slow is, “How much is enough?” More specifically, how much volume do I need to grow? Volume is a function of reps plus sets. There are times when it’s also helpful to add how much total weight is lifted (i.e., work) but for the purposes of bodybuilding, we’re mostly concerned with reps and sets. Several bodybuilding greats such as Dorian Yates have claimed to do relatively low volume using at times only one or two all-out “work sets” per exercise. Others such as Kai Greene are known to use relatively high reps (15–20) on nearly all exercises. So which is it, high or low?
Let’s start with the ideal number of reps to stimulate growth. If you were hoping for a specific number, I’m afraid you’re going to be disappointed. The fact of the matter is the ability of a specific number of reps to stimulate growth is dependent on the condition of the muscle at the time the reps are performed. Because the muscle is in a constant state of adaptation (either increasing its condition, or decreasing its condition), the ideal number of reps to perform is a moving target. Weight load is obviously related to how many reps can be performed during a set, so let’s think about the ideal number of reps in terms of weight load. It’s been established that in an untrained lifter, which can be someone who’s just starting out or, conversely, someone who’s simply taken a long break from lifting, weight loads of ~65–75% one-rep max (1RM) corresponding to 15 to 10 reps is sufficiently heavy to cause significant muscle growth. In veteran lifters, weight loads up to 85% 1RM are required because of the conditioned state of the muscle.
Up to this point, we’ve really only spoken in terms of the number of reps per set. Counting the “total reps” per session is a way of quantifying volume as well. Counting total reps is probably a more accurate way of estimating time under load (TUL). Most of the training scenarios in research use anywhere from 8–12 total reps for single-set training and 24–36 reps for multiple-set training. In a review by Wernbom analyzing 70 different studies, it was concluded that measurable hypertrophy can be achieved using a wide variety of set-and-rep combinations, nevertheless the greatest anabolic response was obtained when using between 30 and 60 total reps per upper and lowerbody muscle group per session respectively. This means that one should try to hit at least 30 reps for each upper-body muscle group, and for those complex muscle groups such as pecs and lats, try to hit 30 reps per plane. - FLEX