Understanding Set Extenders or Intensifying Techniques
There are many set extending techniques or intensifying techniques. Some people call them advanced training techniques, although I’m not a fan of that name.
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High frequency training is catching popularity quickly, but many old school bros and their diehard fans still don’t believe in training muscles multiple times a week. The traditional way of thinking was, let’s dedicate one day to a specific muscle, annihilate it with endless sets, and let it rest the entire week.
But screw tradition, what does the research show? Is once a week the best way to do it or can training muscles more frequently be beneficial?
Before I answer all this, here are a few caveats just so we understand each other crystal clear.
Many bodybuilders and coaches claim the more advanced you get as a lifter, the less frequency you need. They claim a beginner should start with full body training then progress to an upper/lower split as an intermediate, and eventually graduate to training each muscle only once per week once considered advanced.
Well, this first study smashes that idea handily.
One of the first well designed studies compared training frequencies of once per week with 3 times per week in trained subjects (1). Volume was equivalent between groups, so the number of weekly sets was equal. Despite this, the group training each muscle 3 times per week got better growth.
So the whole “train muscles less frequently as you get advanced” idea is completely wrong.
Not only can advanced trainees train muscles frequently, we have evidence to suggest the more advanced you get, the more important frequency becomes. Here’s why:
You can increase the magnitude of muscle protein synthesis or potentially lengthen it by increasing volume within the workout (4). This is not a bad idea, but studies show each workout session seems to have an upper limit for volume before extra sets do nothing and can even compromise hypertrophy (5). Assuming all sets are taken to true failure, this upper limit is around 8-10 sets per workout per body part for most people (17,18).
So as you can see, an advanced lifter would benefit from training muscle groups multiple times a week especially if they’re already near their per workout volume limit for a body part.
I know there’s some meathead who’s about to argue training muscles frequently forces you to train them too closely during the week and not allow for enough recovery.
This isn’t true. If you distribute your number of recoverable sets intelligently throughout the week, there’s no issue with training muscles more than once per week. In fact, full body consecutive day training has been shown to produce the same results as spacing the same workouts with rest days in between, even in trained subjects (7,8).
In fact, trained lifters can recover within 24 hours after 4 sets to failure on a muscle, within 48 hours after 5 sets, and within 72 hours after 12 sets (19,20,21).
Paz et al found 4 sets of bench pressing to failure was recovered within 48 hours (32).
I think high frequency skeptics have had bad experiences with training muscles frequently because they mistakenly took their original high-volume workouts and duplicated them across the week resulting in an exponential increase in weekly volume that couldn’t be recovered from. In reality, increasing frequency means distributing your volume not necessarily duplicating it.
For example, if you’re currently training chest for 20 sets in one day, to increase frequency, you’re not supposed to train chest for 20 sets four days a week. That’s moronic. Instead, you should be training chest for 5 sets four days a week. Same weekly volume, but higher weekly frequency.
Now each set is of higher quality and performance because they’re not done in the same fatiguing session.
When optimal volume is distributed intelligently, studies never show high frequency training to be more fatiguing in advanced subjects. In fact, the opposite occurs.
If you’re able to distribute the same work for a muscle group across the week, you get less fatigue and potentially enhanced recovery due to more frequent blood flow (22,23).
Alright now that we’ve established training with higher frequencies is optimal for advanced lifters, let’s look at it’s relationship with volume because this is where the truth really comes out.
When you train with higher frequencies, the volume you do is of higher quality meaning the sets aren’t as fatiguing, allowing you to lift more weight/reps (9). Think about it, if you did 20 hard sets of legs in a workout, you would be deeply fatigued after about 10 sets. The remaining 10 sets won’t be very productive sets.
But if you split those 20 sets into 3 different workouts with 6-7 sets per workout, all of those sets will be much more productive resulting in more total pounds lifted despite doing the same 20 weekly sets.
However, despite lifting more total weekly pounds with higher frequency training, the muscle growth is generally the same when weekly sets is equal (10). So even though this article is about frequency, it’s vital to remember weekly set volume is still more important.
But with higher frequencies, you’ll likely get extra reps or at worse, get the same reps in a less fatigued state which is why higher training frequencies for hypertrophy is not more injurious no matter what bro split fan boys will say (24). In fact, splitting set volume up into multiple session produced greater muscle activation in the same movement, so if anything, higher training frequencies for hypertrophy training are less injurious (25).
Anyways, when weekly volume (number of sets) is equal, frequency only shows significant additional hypertrophy when going from training a muscle once per week to at least twice per week (11). Going from twice a week to three times a week with the same volume is not as clear, but unlikely to be significantly beneficial (11,12).
James Krieger, one of the researchers behind many frequency studies also found a trend that higher frequency training is more likely to make a difference when weekly volume is above 12 sets because high weekly volumes would surpass the per workout upper volume limit if done in only one workout per week (13).
So beyond training a muscle twice a week, frequency seems to be a tool to distribute volume based on preference or allow for increasing weekly volume without hitting the upper limit per workout (12). But reviews and clusters of studies are hard to look at when training experiencing and frequency comparisons are so different. Let’s look closer at some more studies, especially newer ones.
The first study compared training a muscle 5 times per week with a full body split vs training a muscle once per week with a traditional body part bro split (14).
The full body group gained more muscle in every measure. Strength gains was comparable except squat 1-rep max was higher in the full body group also.
When looking closer at the actual study design, you can make an argument that biceps and triceps were actually trained twice a week in the body part split group, so this could be evidence that there are benefits to training a muscle more than twice a week even when volume is equal.
The next study looked at training a muscle 3 times per week vs training a muscle 6 times per week (15). It found no difference in hypertrophy between groups after 6 weeks and at face value indicates that training a muscle more than 2-3 times a week doesn’t have added benefits when volume is equal.
However, the study design implemented only 12 weekly sets per body part. It’s still possible that with a high training volume, frequency above 3 times a week will produce more gains as it allows you to avoid the per workout upper volume limit mentioned earlier. In addition, this study had the same exercises for the high frequency group throughout the week.
In addition, Colquhoun had a similar design showing 6x trended strongly towards more growth over 3x per week (26). This shows that many of these studies are underpowered because the duration is too short and muscle growth is already a slow process as is.
The infamous unpublished black market study known as the Norwegian Frequency Project done in elite level lifters also found 6x grew more than 3x per week. This study also included women which is note worthy later.
The next study is also interesting (16). It compared training a muscle 3 times per week to 2 times per week in advanced lifters while implementing 36 weekly sets for the legs and 24 weekly sets for upper body muscle groups. This design would allow the 3 times per week group to shine as they would have “optimal” volume distribution. However, the muscle growth was the same between groups which would indicates there is no hypertrophy benefit to training muscles more frequently than twice per week even in advanced lifters.
This study is limited in that volume load was equated between groups which could mask the potential benefits of the higher frequency group.
Gomes et al did find a trend that 5x per week grew more muscle than 1x per week in trained men while experiencing soreness and despite a bad high frequency training program (22).
Bartolomei et al is the only study finding less frequency was superior than higher frequency in trained lifters with a good study design (27). In this study, 2x per week outperform 4x per week, but only in the quads and traps.
However, Crewther et al found 3x outperformed 1.5x per week in trained lifters (28).
Gender is another consideration. If you look at female physiology, they recover better than men within and between training sessions.
Most training frequency studies are done in men, but 2 studies included a mix of trained men and women. They found trends that 3x beats 1x per week (29,30).
The only study done exclusively in trained women was an old one comparing training 7x per week to splitting those same workouts into double training sessions per day (14x per week). Indeed 14x per week grew more muscle in their only hypertrophy measure (31).
Before I sum everything up and give you science based frequency recommendations, it’s important to note that study conclusions are based on averages. You might personally benefit from more or even less than the general recommendations of science because of individual differences.
Science itself even has a paper showing how individuals can respond drastically different to various training frequencies (10). That being said, a higher training frequency is generally better especially if you’re an experienced and know how to distribute your volume along with programming exercises for high frequency training.
With low/moderate training volumes (8-15 sets per body part per week), evidence reveals that:
So if your planned training volume for a body part is low/moderate, you can train it as frequently as you’d like as long as you train it at least twice a week.
With high training volumes (15-25+ sets per body part per week), evidence reveals that:
If your planned training volume for a body part is high (like during a specialization phase), training it at least 3 times a week is most optimal just to be safe.
As always, no matter what your training frequency is, always be sure to distribute volume as evenly as you can.
Stay tuned my friends, I’ll be writing a second part to this article about different training splits and their various pros and cons. Hint, hint, if you couldn’t already tell, body part bro splits suck.
Amirthalingam T;Mavros Y;Wilson GC;Clarke JL;Mitchell L;Hackett DA; “Effects of a Modified German Volume Training Program on Muscular Hypertrophy and Strength.” Journal of Strength and Conditioning Research, U.S. National Library of Medicine, pubmed.ncbi.nlm.nih.gov/27941492/.
Heaselgrave SR;Blacker J;Smeuninx B;McKendry J;Breen L; “Dose-Response Relationship of Weekly Resistance-Training Volume and Frequency on Muscular Adaptations in Trained Men.” International Journal of Sports Physiology and Performance, U.S. National Library of Medicine, pubmed.ncbi.nlm.nih.gov/30160627/.
M;, Marshall PWM;Cross R;Haynes. “The Fatigue of a Full Body Resistance Exercise Session in Trained Men.” Journal of Science and Medicine in Sport, U.S. National Library of Medicine, pubmed.ncbi.nlm.nih.gov/28716692/.
Rodney. “Dissociated Time Course of Recovery Between Strength and… : The Journal of Strength & Conditioning Research.” LWW,
Miranda H;Maia MF;Paz GA;de Souza JAAA;Simão R;Farias DA;Willardson JM; “Repetition Performance and Blood Lactate Responses Adopting Different Recovery Periods Between Training Sessions in Trained Men.” Journal of Strength and Conditioning Research, U.S. National Library of Medicine, pubmed.ncbi.nlm.nih.gov/28195973/.
Gomes, Gederson. “High-Frequency Resistance Training Is Not More Effective… : The Journal of Strength & Conditioning Research.” LWW,
Abaïdia AE;Delecroix B;Leduc C;Lamblin J;McCall A;Baquet G;Dupont G; “Effects of a Strength Training Session After an Exercise Inducing Muscle Damage on Recovery Kinetics.” Journal of Strength and Conditioning Research, U.S. National Library of Medicine, pubmed.ncbi.nlm.nih.gov/27227793/.
Ochi, Eisuke, et al. “Higher Training Frequency Is Important for Gaining Muscular Strength Under Volume-Matched Training.” Frontiers, Frontiers, 28 May 2018, www.frontiersin.org/articles/10.3389/fphys.2018.00744/full.
Hartman MJ;Clark B;Bembens DA;Kilgore JL;Bemben MG; “Comparisons between Twice-Daily and Once-Daily Training Sessions in Male Weight Lifters.” International Journal of Sports Physiology and Performance, U.S. National Library of Medicine, pubmed.ncbi.nlm.nih.gov/19124903/.
Colquhoun RJ;Gai CM;Aguilar D;Bove D;Dolan J;Vargas A;Couvillion K;Jenkins NDM;Campbell BI; “Training Volume, Not Frequency, Indicative of Maximal Strength Adaptations to Resistance Training.” Journal of Strength and Conditioning Research, U.S. National Library of Medicine, pubmed.ncbi.nlm.nih.gov/29324578/.
Bartolomei, Sandro. “A Comparison Between Total Body and Split Routine… : The Journal of Strength & Conditioning Research.” LWW, 2020,
Crewther, B T, et al. “The Effects of Two Equal-Volume Training Protocols upon Strength, Body Composition and Salivary Hormones in Male Rugby Union Players.” Biology of Sport, Institute of Sport in Warsaw, June 2016, www.ncbi.nlm.nih.gov/pmc/articles/PMC4885621/.
“Comparison of 1 Day and 3 Days Per Week of Equal-Volume… : The Journal of Strength & Conditioning Research.” LWW, journals.lww.com/nsca-jscr/Abstract/2000/08000/Comparison_of_1_Day_and_3_Days_Per_Week_of.6.aspx.
Thomas, Michael, and Steve Burns. “Increasing Lean Mass and Strength: A Comparison of High Frequency Strength Training to Low Frequency Strength Training.” TopSCHOLAR®, digitalcommons.wku.edu/ijes/vol9/iss2/5/.
M;, Häkkinen K;Kallinen. “Distribution of Strength Training Volume into One or Two Daily Sessions and Neuromuscular Adaptations in Female Athletes.” Electromyography and Clinical Neurophysiology, U.S. National Library of Medicine, pubmed.ncbi.nlm.nih.gov/8187678/.
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