High vs. low reps: which is better?

Fitness industry contains a curious paradox – although it is developing so rapidly and flourishes with emerging research and new knowledge, certain views remain unchallenged for longest stretches of time!

The “high vs. low reps” debate is a perfect example – and I’m certain that you have come across it yourself if you’ve been on your journey for a while.

“High reps are for toning!”

“You can only build muscle by lifting very heavy!”

“Only use certain rep ranges for certain goals!”

…do any of these statements sound familiar?

If yes, you are not alone! But does using high vs. low reps determine the outcomes of your programming, and if it does, what approach should you take?

Let’s investigate together! This science-packed blog will take you on a journey from learning about different types of muscle fibres all the way to recent research, and the findings may change the way you train forever!

Muscle fibres 101

To understand the reasoning behind using high vs. low rep ranges, we first need to get into a little bit more detail on the structure of our muscles!

In a nutshell, our muscles are comprised of fibres that can be described as either fast or slow twitch. It was an evolutionary advantage for us to develop both types – and most people have a 50/50% distribution of them in all muscle groups, give or take. 

These are designed for efficiently taking over different tasks.


  • Contract when low levels of force are required
  • Can remain engaged for prolonged periods
  • Are amazing for long-term sustained activities – such as walking or standing for extended periods! Our hunter gatherer ancestors really took advantage of their slow twitch muscle fibers when sustaining chases or looking for food sources all day without stopping!


  • Contract when lots of power is needed
  • Can only remain engaged for brief periods – after which they become fatigued
  • Give us the ability to sprint, jump, throw and fight – which, again, was an amazing evolutionary advantage for our ancestors

Initial research on high vs. low reps

Identifying different types of muscle fibres was nothing short of a breakthrough in exercise science!

Once the differences between the 2 types were discovered, it was also concluded that they respond differently during varying exercise types. For example, it was believed that slow twitch fibres are recruited during endurance aerobic activities or high rep resistance training exercise. Fast twitch fibres were thought to require sprinting or heavy load weight training to be recruited – and were also identified as responsible for muscle growth.

As a result, the following system of recommendations has been developed:

  • The repetition range for growing muscle is using a load that causes fatigue between 8-12, as this activates fast twitch muscle and stimulates release of hormones responsible for muscle growth
  • And consequently – “only low reps build muscle”, a belief that is very persistent even today!

The issue? Research methods leading to these conclusions may not have been comprehensive enough to paint the full picture!

For example, muscle activation was measured only by the use of surface electrodes detecting the electrical activity of muscle fibres (known as EMG). Almost all the original research has shown a higher EMG amplitude with lower reps than high reps, leading virtually everyone to believe that low reps were the best for muscle growth.

Challenging the beliefs

Recent studies found different results from using a wider variety of methods. Current approaches include ultrasound, various scans, as well as studying metabolic changes in actual samples of muscle tissue obtained before and after exercises. To put it simply, researchers have much more tools in their labs – which leads to very different findings!

One of the lead researchers in re-examining “high vs. low reps” myths is he Canadian Professor, Stu Phillips. Dr. Phillips reasoned that muscle fibres are recruited on a ‘needs basis’, called the size principle in exercise physiology. In a nutshell, this means that no matter when one gets close to failure – whether at 6 reps or at 30 – fast twitch muscle fibres will come to the rescue regardless to help complete the movement!

Multiple studies were conducted by Phillips’s research group, as well as other researchers, with the core findings suggesting that:

  • There is no difference between fast twitch fibre muscle recruitment between the low and high reps, PROVIDING the exercise was taken to failure. This is a very important distinction, as lifting a weight that is not at all challenging for you for a couple of reps will not promote muscle growth!
  • Anabolic hormones released in response to resistance training at any rep range had no effect on muscle growth
  • Older methods used to assess muscle fibre recruitment were proven not accurate
  • Muscle strength is best developed with lower repetition ranges, typically under 10 reps per set

So, even though the “low reps for muscle growth” concept is still cited back and forth, it’s based on very outdated information that appears largely oversimplified!

The main take home message? Effort is king – no matter what rep range is used!  Muscle is activated on an effort basis, and as you approach exercise failure, both fast and slow twitch fibres and maximally activated and exhausted.

Practical tips from recent research

In addition to the above, here are some practical tips on programming based on recent research!

  • Repetitions across a wide spectrum, from 6 and above, have the ability to engage fast twitch muscles and promote muscle growth.
  • Effort, causing fatigue or muscle failure, is the key factor for muscle growth
  • Certain exercises do not suit the low rep ranges, such as many exercises for the calves, lower back, core, shoulder stabilizers and forearms. No need to injure yourself trying, as results can be identical with lighter load and higher reps!
  • If you are someone who is intimidated by lifting heavy with low reps, or are recovering from an injury, fear not – you can still achieve great results with lighter load.
  • Similarly, having limited access to equipment – e.g. training at home or outdoors, does not have to limit your progress. Again, if effort is high, the results can be identical to going heavy!
  • Long term programming and body composition results are highly dependent on training variety. You should be constantly changing yourself in different ways! Having programs that utilize a wide selection of rep ranges can prevent boredom and hit the target muscles in all sorts of different ways.

My Booty & Core Program is largely built on the above principles and uses a variety of approaches to challenge you with no to minimal equipment! Find out more about the Program HERE - and sign up via this LINK!

I hope you found this information useful – and that it inspires you to try a variety of different approaches to training!

Much love,

Tony Boutagy and Rach