How often should you train each muscle per week? Once a week? Twice a week? Somewhere in between? A sizeable body of research has emerged over the last decade suggested that training each muscle twice a week might be superior for both strength and muscle growth. For that reason, this has become the most common recommendation this day. But not so fast. You can gain muscle hitting each muscle less often than twice a week under one condition…
Many of the older studies that compared training each muscle one versus two times per week failed to equalize the volume (number of weekly sets) between the test groups. As you know if you read my previous blog on tracking your training volume, counting your weekly sets is an excellent metric to have on your radar to make sure you’re doing enough training to optimize gains, but not too much to tip you into overtraining.
Recently, one group of researchers carefully designed a study where the weekly training volume was matched. They discovered something very interesting that has helped to finally answer this question, “How often should you train each muscle per week?” But before reviewing this study, let’s look at what people are doing in the real world to build muscle.
Frequency And Volume Practices Of Successful Competitive Bodybuilders
In 2013, a survey of 127 competitive male bodybuilders was conducted and the results were published in the Journal of Strength And Conditioning Research (Hackett, et al). There were three interesting findings about bodybuilders who had reached the competitive level.
1. The majority did approximately 4 sets per exercise of 4 different exercises per muscle group, totaling approximately 16 sets.
2. The number of workouts per week ranged between 5 and 6 sessions a week.
3. The majority (69%) trained each muscle only once a week using body part split routines. All 16 of their sets were performed in one weekly session.
None of this is surprising. This style of training is fairly standard for bodybuilders who are gifted and advanced enough to compete. (High volume, high number of weekly workouts, multiple exercises per body part, each muscle only hit once a week).
But despite the fact that these bodybuilders walk around with some of the most impressive bodies on the planet, not all of their methods have been tested in a scientific manner. It has simply been assumed that if the best competitors are doing it, then it must work for everyone.
Scientific-minded people often respond by noting that athletes who are genetically superior and or who use performance-enhancing drugs may be getting results in spite of their training methods, not because of them. You also may hear comments like, “Sure they look great, but if they used a more optimal training schedule, they’d look even better.”
Critics of bodybuilding-style training methods suggest that the genetically average and drug-free, as well as people who simply train for health, recreation, and looking better, might do worse following the methods of advanced competitors who have certain advantages.
One of the biggest questions about bodybuilding-style training has been whether training each muscle only once a week – an unquestionably low frequency – is optimal. Another question is whether the average trainee would get better results training each muscle more often (closer to twice a week, or somewhere in between, like once every four to six days).
Weekly Training Volume, Training Frequency And Muscle Growth
To answer this question scientifically instead of just asking athletes what works for them, research on training frequency began in earnest about a decade ago. In evidence-based bodybuilding, this has been one of the hottest topics right to this day.
A number of studies have compared the effects of once versus twice a week frequencies. These studies produced mixed results, but many of them suggested that training each muscle twice a week might in fact be superior to once a week for both strength and muscle growth. The problem is, there were limitations with many of the older studies.
The most blatant flaw was when they didn’t match the weekly volume between the test groups. Another is that the subjects were beginners with no training experience.
Based on our current understanding of the muscle growth process, we know there’s a direct relationship between volume and growth. Increasing volume (adding sets and exercises) increases muscle growth, up to a point. (Do too much however, and you end up under-recovered and over-trained)
Suppose a lifter increased training frequency from once to twice a week, and in the process, bumped up their weekly sets from 8 to 16. Assuming the increase didn’t lead to overtraining, we would predict that the 16 sets per week group would make more gains because they did twice the work.
But if we really want to know the effect of training a muscle once or twice a week, we have to control that all-important variable: weekly volume
How Often Should You Train Each Muscle: What The Latest Research Says
In 2021, a group of exercise scientists from Brazil (Bartolomei et al) designed a study that was controlled by equalizing the volume between both test groups.
Even though there are piles of research papers on the training frequency topic, this was the first one to ever compare the effects of one versus two sessions per muscle group per week in trained subjects when the volume (sets) were equated.
The study was further improved by using only subjects who had substantial training experience (2 to 8 years of previous lifting) and they were not using steroids. In addition, testing was done in multiple measurements including muscle strength, size, and endurance. Muscle growth was meticulously measured, including ultrasound testing for actual muscle thickness.
The subjects in this study followed a lifting program using exercises, sets, and reps similar to what bodybuilders use in traditional muscle-building workouts. One group trained each muscle 2 times per week with 8 sets per workout (16 sets per week), and the other trained each muscle 1 time per week with 16 sets per workout (also 16 sets per week, ie, the volume was equated). Every set was taken to failure (RPE 9.5 to 10), which helped equalize for the intensity of effort.
Even though the volume was equated and the subjects studied were a homogenous group, the researchers still hypothesized that training muscle groups twice a week would induce significantly greater gains in muscle size, strength and endurance compared to training muscle groups only once a week, with the same number of weekly sets in total.
Contrary to the hypothesis, after 8 weeks, there was no significant difference in muscle gain between the groups. Here was the main finding of the study:
Training a muscle group only once a week is as efficient as training twice a week for increasing muscle size, strength and endurance, given the condition that weekly volume is the same.
These results run contrary to much of the previous research, which had led almost the whole fitness industry to make strong recommendations to train each muscle twice a week, not once a week.
It hasn’t been uncommon in the fitness community, especially on social media, for bodybuilders who work each muscle once a week to be mocked and called “bros” and their methods “bro science.” They were criticized if their only evidence was “It works for me” or “I’m winning contests.” But now there is evidence.
In this In their own words, the researchers said,
“This study shows that training muscle groups once and twice per week are both viable strategies to increase muscle strength, endurance and hypertrophy.”
What made the difference was how well the variables were controlled. Not only did they equate for volume, they also noted that in many of the previous studies the subjects had been untrained beginners, middle-aged men, or elderly women. In these populations, doing a high volume in one session (16 sets in this case) may have been far more work than they could handle without seeing overtraining symptoms that actually held back gains. (Or, in reverse, beginners often see greater gains than experienced lifters, regardless of the program used).
There was one new and interesting finding, that was partially in agreement with the hypothesis: They noted a small but possibly meaningful increase in upper body endurance with two training sessions per body part per week. It’s also worth noting that there were minor differences in the effect sizes that may have favored the twice a week condition, they simply were not significant enough to say it was superior.
While hypertrophy gains seem similar with higher and lower frequency training if volume is equated, there is also some evidence that higher training frequencies are better for strength gains. When choosing a training schedule that’s something to consider if strength is a priority for you. There is a reason powerlifters don’t follow competitive bodybuilder split routines.
Limitations To The Existing Research
While the Brazilian study improved on previous study designs, it still had limitations, as most studies do. One was that it only lasted 8 weeks. Muscle growth is a slow process, and it’s possible results may have diverged over a longer time period.
Also, even though the subjects were trained, they did not all train the same way prior to enrolling in the study. Some of them reported doing only 10 sets or less per muscle group on a regular basis. Increasing to 16 sets alone may have been an overload that unlocked more muscle growth.
Similarly, the majority of the subjects were only training each muscle once a week before the study, so the group that did twice a week may have been seeing additional muscle growth purely due to the novelty effect. That leads us to another question…
What About Using Different Training Splits And Frequencies Throughout The Year?
It’s safe to say that both higher and lower training frequencies can be effective when the volume is matched and the program design is appropriate for an individual. That being the case, since muscle growth may be stimulated by novelty, some experts are now suggesting that changing your training frequency throughout the year may be a good strategy to optimize muscle growth.
More long term research is needed to confirm this, but the evidence supports the idea that if you change your training frequency over the course of a year instead of always sticking to the frequency that you’re used to, this might produce better gains.
This means that while we should pay attention to how we respond personally to various training frequencies, and you can choose programs based on your personal preference alone, we might want dispense with the idea that there even exists one frequency that is superior to others across the board.
In other words, it doesn’t hurt to train each muscle twice a week at times, once a week at times, and somewhere in between at other times. You may also want to try different split routines as well.
In practical terms this means you might do a 2-day split for a few months, then switch to a 3-day, 4-day, or even 5-day split (the classic “bro split). It’s not wrong to think even full-body workouts (no split) could be put into the mix even as an advanced physique athlete, as long as the desired training volume can be achieved by the end of each week.
If you’ve heard advice before to “mix things up,” we now may want to extend that beyond simply changing exercises and lifting techniques, but also changing up your lifting frequency regularly rather than looking for one “best” way. This doesn’t mean program hopping, but it might mean trying a new training schedule as often as every three months or so.
This is one of the reasons that we offer multiple training program options for our members at Burn the Fat Inner Circle. In fact, we have over a dozen flagship training plans and are now adding new ones every quarter.
One of the popular body part splits is the 4 day split with 4 workouts per week. You can see that means each muscle is worked only once per week. We call this the 4 X 4 Muscle and Physique program.
This is our newest program at Burn the Fat Inner Circle that’s schedule to be released next week – free for all current members.
If you’re not a member yet and you’re interested in checking out a wide variety of different split routines designed for optimizing muscle gains and physique transformation you can learn more on the pages below:
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Train hard and expect success!
Tom Venuto, Author of Burn the Fat, Feed the Muscle Guide To Flexible Meal Planning
Founder and CEO, Burn the Fat Inner Circle,
The support community for all-natural, no-BS body transformation
About Tom Venuto
Tom Venuto is a natural bodybuilding and fat loss expert. He is also a recipe creator specializing in fat-burning, muscle-building cooking. Tom is a former competitive bodybuilder and today works as a full-time fitness coach, writer, blogger, and author. In his spare time, he is an avid outdoor enthusiast and backpacker. His book, Burn The Fat, Feed The Muscle is an international bestseller, first as an ebook and now as a hardcover and audiobook. The Body Fat Solution, Tom’s book about emotional eating and long-term weight maintenance, was an Oprah Magazine and Men’s Fitness Magazine pick. Tom is also the founder of Burn The Fat Inner Circle – a fitness support community with over 52,000 members worldwide since 2006. Click here for membership details
Bartolomei, S, et al, A comparison between total body and split routine resistance training programs in trained men. J Strength Cond Res 35(6): 1520-1526, 2021.
Hackett D et al, Training Practices and Ergogenic Aids Used by Male Bodybuilders, Journal of Strength and Conditioning Research, Volume 27 – Issue 6 – p 1609-1617, 2013.
Schoenfeld BJ, Grgic J, Krieger J. How many times per week should a muscle be trained to maximize muscle hypertrophy? A systematic review and meta-analysis of studies examining the effects of resistance training frequency. J Sports Sci. 2018 Dec 17:1-10.
Schoenfeld BJ, et al, Effects of resistance training frequency on measures of muscle hypertrophy: A systematic review and meta-analysis, Sports Medicine, 46(11), 1689-1697, 2016