It’s not uncommon for individuals to train with only a single rep range in their whole program.
Of course, this isn’t bad, positive adaptations will unquestionably still take place.
But as we’ll examine in this article, training with different rep ranges may provide a variety of potential benefits.
When I say training with different rep ranges, I’m mainly referring to training an exercise with different rep ranges on different days of the week.
But training a specific muscle group with different exercises performed with different rep ranges also applies. For example, you may train your quads with leg presses, squats, and leg extensions either in a session or weekly schedule. You may train the squats with sets of 6 repetitions, the leg extensions with sets of 12 reps, and the leg extensions with sets of 25 repetitions.
Let’s dive straight in.
Table of Contents
Part I: What Combining Rep Ranges Does Not Do
Before detailing what training with different rep ranges can do, it’s worth understanding what it doesn’t do, as a misconception around this exists.
As mentioned in other articles, per set, reps between 6 and 35 are similarly effective for increasing overall muscle size, provided those reps are performed to or close to failure.
Some speculate despite the similar increases in muscle size, low and higher reps may grow different muscle fiber types.
Very broadly, muscles contain slow and fast-twitch fibers.
Slow-twitch fibers are highly fatigue resistant but produce low forces. Fast-twitch fibers produce high forces but are very fatigable.
It’s speculated lower reps with heavier loads preferentially grow fast-twitch fibers, while higher reps with light loads preferentially grow slow-twitch muscle fibers.
So combining low and higher reps in a program ensures optimal development of all fiber types.
Yet, the evidence suggests this isn’t quite correct.
A meta-analysis by Grgic et al. combined the results of 5 studies.
In the papers, the high reps involved around 20-40 reps performed to or close to failure with loads between 30 and 50% one-rep max, while the low reps involved 3 to 10 reps performed to or close to failure with 75% to 90% one-rep max loads.
It was found both low and high reps similarly grew the slow and fast-twitch muscle fibers.
Thus, so long as reps are performed to or close to failure, both low and higher reps are similarly effective at developing slow and fast-twitch fibers.
Part II: What Combining Rep Ranges Can Do
Though different rep ranges produce similar hypertrophy, including similar slow and fast-twitch fiber hypertrophy as just established, other fitness attributes are optimized with either higher or lower reps.
So training with different rep ranges can be a highly efficacious way to concurrently develop different fitness attributes.
This can be great for overall health and well-being, a point notable for non-professional or non-competitive lifters.
Lower reps better optimize the maximum load you can lift for a single rep (termed your one-rep max), via increasing your skill with heavier loads and better promoting neural adaptations that enhance your ability to recruit and expose your muscle fibers to tension.
The literature consistently finds strength is notable for longevity (one, two, and three). One cohort study found regardless of muscle mass, low muscle strength was independently associated with an elevated risk of death from all causes in individuals above the age of 50.
Lower reps with heavier loads may potentially be superior for bone strength. Though high reps can certainly enhance bone density, the literature seems to more consistently find heavier loads produces greater effects (one and two).
Higher reps, of course, better promote endurance adaptations.
Numerous studies indicate higher reps more effectively increase the number of reps you can complete with a given percentage of your one-rep max.
These endurance gains may be explained by higher reps better-producing mitochondria and blood vessel alterations.
Mitochondria are components within muscle fibers that play a crucial role in generating energy for things including muscle contraction, and more blood vessels increase the ability of the body to deliver oxygen and nutrients to the muscle, as well as remove waste products.
For example, a 2019 Canadian study found as we’d expect, training to failure with a 30% one-rep max load was similarly effective for slow and fast-twitch fiber hypertrophy to an 80% one-rep max load, yet increases in the content of several mitochondrial-related proteins were superior when training with a 30% one-rep max load.
Having healthy mitochondria function and numbers plays a crucial role in overall health.
As for blood vessels, one study actually found no statistical difference in capillarization between training with 20-25 reps or 8-12 reps, yet the percentages did favor the 20-25 reps.
Physiologically, there’s reason to believe higher reps would more consistently produce the formation of new blood vessels, as the stimuli that achieves this is hypoxia and shear stress, two things that are going to be enhanced with higher reps.
Over the long-term, concurrent development of various fitness attributes achieved through training with different rep ranges may not only benefit overall health but also potentially hypertrophy.
Let’s explore this.
Part III: Training With Different Rep Ranges Superior for Hypertrophy?
Most studies find no difference in hypertrophy between training with a single rep range or training with different rep ranges (one, two, three, four, five, six, seven, and eight).
But a limitation is these studies largely last 12 weeks or less.
In the long-term, as just alluded to, there could be a difference between the two.
For example, a 2003 study from the USA found in previously untrained women training for 9 months, compared to training with the same rep range, training with different rep ranges per week ultimately lead to greater increases in fat free mass.
Now, this is far from strong evidence, it’s just one study conducted on previously untrained women, and fat-free mass is far from the most precise muscle growth measurement.
Nevertheless, an array of potential paths exist by which training with different rep ranges could benefit hypertrophy.
Firstly, we know lower reps optimize neural adaptations that enhance your ability to recruit and expose your muscle fibers to tension.
This is notable because mechanical tension is the primary hypertrophy stimulus. That is, muscle fibers can detect the tension they produce and transduce it into a signaling cascade that produces hypertrophy.
Thus, having a better ability to recruit and expose your muscle fibers to tension via neural adaptations can enhance the overall mechanical tension you experience during your set of repetitions.
The fact is not all individuals have an equal capacity to recruit and expose their fibers tension. Moreover, it can only depend on the muscle in question.
One study established around 15.5% of the muscle activation potential of the quadriceps was inaccessible to individuals, whereas these values were 5% for the elbow flexors and calves.
So in cases where muscles cannot be easily recruited from the onset, neural adaptations from lower reps may change this and enhance one’s ability to expose a muscle to greater overall mechanical tension.
Secondly, the endurance benefits provided by higher reps, such as the formation of new blood vessels like capillaries may have hypertrophic benefit.
Interestingly, some data indicates capillarization (the formation and development of a network of capillaries) may have associations with hypertrophy.
A 2017 study from Canada found in older men, those with the higher capillarization of fast-twitch muscle fibers from the vastus lateralis ultimately saw the greatest fast-twitch fiber hypertrophy in response to lifting weights.
Another 2019 study found similar things in older men, subjects with greater capillarization of vastus lateralis fibers saw greater vastus lateralis hypertrophy.
In younger individuals, a fascinating 2022 study from Canada found those who saw the greatest fast-twitch fiber capillarization from aerobic training in the vastus lateralis, tended to see greater vastus lateralis fast-twitch fiber growth in response to 10 weeks of resistance training.
On top of this, it’s important individuals recognize lifting weights is fairly aerobically demanding, despite what it may seem.
For example, a 200m sprint (something considered very anaerobic) still involves a 29% contribution from the aerobic system.
Also, recovery between sets, performance on later sets in a session, and recovery between sessions are going to be reliant on the aerobic system to a large degree.
So the aerobic adaptations provided by higher reps can enhance all of these things.
Finally, higher rep ranges are more painful than lower reps, but developing this capacity to withstand pain and continue can be beneficial. Getting accustomed to the pain associated with a set of 20-30 reps to failure is going to make a set of 8 reps to or close to failure feel like a breeze.
I should note dedicated aerobic training is going to be superior for aerobic adaptations (especially central adaptations related to the heart) versus higher reps, so this is also one reason why I believe aerobic training can be of great utility to lifters, plus it just makes you feel great. More on this in the future…
In any case, I still believe high reps have their place even if you’re performing aerobic training, as remember mitochondria and blood vessel adaptations are specific to the muscles being trained, so high reps can help spur aerobic adaptations in muscles not involved in your dedicated aerobic training modality.
Part IV: Training With Different Rep Ranges Superior for Strength?
The research tends to find that training with different rep ranges does produce greater strength adaptations versus training with a single rep range.
However, a notable limitation is the groups training with different rep ranges ultimately train more frequently with lower reps versus the groups training with a single rep range, so this may explain the greater strength gains rather than using the different rep ranges per se.
So more research is needed to determine if training with different rep ranges truly enhances long-term strength gains.
In any event, this data at least shows training with different rep ranges is unquestionably going to be effective for strength gains.
Part V: Summary
Both low and high reps similarly increase fast and slow-twitch fiber size, so training with different rep ranges on the assumption the different rep ranges preferentially target slow or fast-twitch growth is incorrect.
However, training with different rep ranges can be effective for concurrently developing different fitness attributes, something beneficial for overall health and longevity.
Furthermore, there are potential avenues by which training with different rep ranges could potentially enhance long-term muscle growth.
As for strength, more research is needed to determine if training with different rep ranges is superior.