Healthier Life: The science of size and building muscle effectively Published July 3, 2018 By Guy Leahy Health Promotion Flight KIRTLAND AIR FORCE BASE, N.M. -- Some of the most common resistance training questions I receive relate to increasing muscle size. With this in mind, here are some guidelines for using RT to maximize muscle growth. Let’s start by talking sets and reps. At one time, scientists thought there was a “repetition continuum,” which meant specific adaptions from RT were dependent on the number of reps performed per set. For example, sets of 3-5 reps built strength/power, sets of 8-12 reps increased muscle fiber diameter (a process known as hypertrophy), and sets of greater than 15 reps increased muscular endurance (such as push-ups). Recent research indicates this “continuum” is mostly untrue. For building muscle, the number of reps doesn’t matter all that much; sets anywhere from 6-25 repetitions are equally effective in increasing muscle hypertrophy, as long as the sets are performed to fatigue. Fatigue is critical; to maximize muscle size, all non-warmup sets need to be performed until you can’t lift the weight anymore. Sets of five reps or less to fatigue appear to improve strength a bit more than 6–25 reps and hypertrophy with less than five reps may be less, but the differences are small. As far as sets go, one set completed to fatigue will result in an increase in muscle size; 2-3 sets are better, and 4-6 sets are even more superior. There isn’t good data beyond six sets, so we don’t know if there are some set numbers which result in diminishing returns. What is important is the total number of sets per muscle group, per week. An optimal range appears to be between 12 and 18 sets per week. One common component of RT programs is to combine multi-joint exercises, such as a bench press, pull-up or leg press, with single joint exercises, such as a pec fly, bicep curl or leg extension. The idea behind this is to provide extra size stimulus by working muscles in isolation. Recent studies have tested this hypothesis and have found no evidence that this is true. Let’s use the biceps muscle as an example. Assuming total volume is held constant, bicep curls only, pull-ups only and bicep curls plus pull-ups all produce the same increases in biceps muscle size. This calls into question whether isolation exercises need to be performed at all, since adding biceps curls to pull-ups did not produce hypertrophy beyond what each exercise produced singularly. Does frequency matter? In untrained subjects, this does not appear to be the case, if weekly volume is the same. For example, if the goal is to reach 12 sets per week for any muscle group, 12 sets at 1 day/week, 6 sets at 2 days/week or 4 sets at 3 days/week all produce similar results. In trained subjects, however, frequency may matter to some extent. Research indicates trained subjects respond better to a three-times- per-week schedule than one time per week; and six times per week is no more beneficial than three sessions per week. The duration of between-set rest periods also effects hypertrophy. Studies that use one-minute rest intervals consistently show a blunted hypertrophy response compared to three and five rest intervals. The minimum recommended rest interval from published research to date is two minutes. Certain types of endurance training also appear to compromise hypertrophic responses. This “interference effect” is well documented for running. Running more than three days per week and/or more than 20-30 minutes per session will interfere with lower body strength, size and power; there is no effect on the upper body. Not all aerobic exercise modes produce interference; cycling and rowing do not have an interference effect. We do not have data on swimming or elliptical training, so we don’t know if an interference effect exists with those modes. There you have it — some evidence-based tactics to build muscle. For more information, contact Guy Leahy at 846-1186 or via email at guy.d.leahy.civ@mail.mil.