: How many reps are ideal for increasing muscle mass? Research In Ultimate Bodybuilding: The Master Blaster's Principles of Training and Nutrition Joe Weider says the following: I learned that the best repetition range

Very short answer : Low reps with high weights build muscle mass. High reps with low weights build endurance/stamina. Ideal reps ~ 8.

But you must try it with heavier weights and keep increasing the weight little by little over time. If you don't increase weight, you will not get results. When you keep on doing the same weights you get into maintenance zone. So be daring and believe that you can indeed lift more than you can imagine. :-)

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A comment pointer me to the website of Dr. Brad Schoenfeld, an apparent expert in the effects of training on muscle hypertrophy. He wrote an article for T-Nation in 2012 entitled Four Reasons You're Not Gaining Muscle which provides a much better answer to this question:

Mistake #1 : You're not varying your rep range.

The optimal number of repetitions for hypertrophy-oriented training is a source of ongoing debate in the fitness field. Although the research is by no means conclusive, evidence indicates that a moderate rep range (approximately 6-12 reps per set) is generally best for maximizing muscle growth.(1)

This is often referred to as "bodybuilding-style training" as it seems to provide the ideal combination of mechanical tension, muscle damage, and metabolic stress – the three primary factors involved in hypertrophic gains.(2) The problem is, most lifters seem to think this means all training should be carried out in this rep range and thus they rigidly adhere to the same loading patterns. Wrong assumption.

Understand that maximal muscular development is built on a foundation of strength. This mandates that at least some of your sets need to be carried out in the lower rep ranges (1-5 reps per set).

Stronger muscles allow you to use heavier weights, and thus generate greater muscular tension in the moderate repetition ranges that optimally stimulate hypertrophy. By increasing muscle tension without compromising metabolic stress, you're setting the stage for enhanced growth.

On the other end of the spectrum, high rep sets (in the range of 15 to 20 reps per set) also have a place in a hypertrophy-oriented routine. Provided that training is carried out at or near your sub-rep max, lower intensity sets help to increase your lactate threshold, the point at which lactic acid rapidly begins to accumulate in working muscles.

The problem with lactic acid is that beyond a certain point its accumulation interferes with muscle contraction, reducing the number of reps you can perform.(3) (Technical note: it's actually the H+ component of lactic acid that hastens the onset of muscular fatigue.)

Here's the good news: Higher rep training increases capillary density and improves muscle buffering capacity, both of which help to delay lactic buildup. The upshot is, you're able to maintain a greater time under tension at a given hypertrophy-oriented workload. In addition, you develop a greater tolerance for higher volumes of work–an important component for maximizing hypertrophy (see Mistake #2 ).

Take home message: Optimal muscle development is achieved by varying your rep range over time. This is best carried out in a structured, periodized program. Both undulating and linear periodized approaches can work, depending on your goals. Whatever scheme you employ, though, make sure you include the full spectrum of loading ranges.

Sure, hypertrophy training is probably best achieved with moderate rep sets, but higher and lower intensities are nevertheless important for optimizing muscular development.

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Is there an ideal rep range for increasing muscle mass, and if so, what is it?

There isn't ideal, but generally there is wide range, like 4-15. You must understand that everybody is different, for one low rep training will be the best and for other high reps will be good even on those complex exercises like bench presses and squats. Anyway for most people it's best to do less reps on multi-part complex exercises (presses, squats etc) and more reps on isolated exercises.

How much difference does the rep range make?

Depends on your body.

Why is there so much contradiction between sources?

Understanding your own body is the answer for many fitness questions :)

I'm not native English speaker, so if I wrote something wrong, please,let me know in comments :)

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Strength Endurance Continuum

The strength endurance continuum shows that strength and endurance are at opposing ends of a spectrum. Focusing on one end of the spectrum (for example strength) sacrifices the other (endurance).

People tend to view this scale as being a trade-off between strength and size, but as you'll see in a bit, this isn't entirely true.

Low Repetitions vs High Repetitions

In a paper entitled Muscular adaptations in response to three different resistance-training regimens: specificity of repetition maximum training zones, the authors concluded that only low-repetition (3-5 reps) and intermediate-repetition (9-11 reps) groups hypertrophied, with no significant increases shown in the high-repetition (20-28) group:

All three major fiber types (types I, IIA, and IIB) hypertrophied for the Low Rep and Int Rep groups, whereas no significant increases were demonstrated for either the High Rep or Con groups.

Moreover, the high-repetition group were shown to improve aerobic power and stamina:

The High Rep group, however, appeared better adapted for submaximal, prolonged contractions, with significant increases after training in aerobic power and time to exhaustion. Thus, low and intermediate RM training appears to induce similar muscular adaptations, at least after short-term training in previously untrained subjects.

Resistance Training Load

The paper shown in another answer entitled Resistance exercise load does not determine training-mediated hypertrophic gains in young men came to the conclusion that training load (percentage of 1RM, from 30% to 80%) in combination with training volume (1 or 3 repetitions) had no affect on hypertrophic gains.

In accordance with our previous acute measurements of muscle protein synthetic rates a lower load lifted to failure resulted in similar hypertrophy as a heavy load lifted to failure.

High vs Low Intensity

Update: This section is removed in response to comments as it's not related to the discussion and only misleads.

In Muscular adaptations to combinations of high- and low-intensity resistance exercises, the authors performed the following experiment:

Acute and long-term effects of resistance-training regimens with varied combinations of high- and low-intensity exercises were studied. Acute changes in the serum growth hormone (GH) concentration were initially measured after 3 types of regimens for knee extension exercise: a medium intensity (approximately 10 repetition maximum [RM]) short interset rest period (30 s) with progressively decreasing load ("hypertrophy type"); 5 sets of a high-intensity (90% of 1RM) and low-repetition exercise ("strength type"); and a single set of low-intensity and high-repetition exercise added immediately after the strength-type regimen ("combi-type").

They concluded that a combination of high and low intensity was more effective for optimizing the strength adaptation.

Answers to Questions

Is there an ideal rep range for increasing muscle mass, and if so, what is it?

Low to intermediate rep ranges (3-11 repetitions) have been shown to be more effective than high repetition ranges (20-28 repetitions). What happens between 11-20 repetitions isn't covered in the papers I was able to find, but I suspect that going as high as the 15 repetitions in Joe Stoppani's program will not be detrimental to gaining muscle.

I think it's important to get out of the mindset that rep range alone is the only factor to consider to increase muscle mass.

How much difference does the rep range make?

A big difference. Regardless of the rep range your body will change, be it for strength/mass or endurance.

Why is there so much contradiction between sources?

The biggest contradiction for me is that 8-12 repetitions is "best". This falls within the low to intermediate range, but there is no evidence (that I could find) to suggest that 8-12 is better than 5-8. Likewise, I suspect that same for Joe Stoppani's 12-15 rep range.

I can only imagine that, as in Joe Weider's case, people have anecdotally reported better results, and they have been taken as fact. This is a huge assumption of course.

Other Considerations

There are other variables that aren't covered in this answer. For example, the age and sex of the person training, and the amount of training experience someone has.

I only read the abstracts of the papers, because I'm not qualified to understand a lot of what's in the paper, so take it with a pinch of salt.

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A research paper entitled Resistance exercise load does not determine training-mediated hypertrophic gains in young men written in 2012 showed that a weight as low as 30% of 1RM can contribute to muscle growth, as long as you work to failure, which is around +30 reps and for >2 sets:

There was no correlation between phosphorylation of any signaling protein and hypertrophy. In accordance with our previous acute measurements of muscle protein synthetic rates a lower load lifted to failure resulted in similar hypertrophy as a heavy load lifted to failure

It is hard to provide any hard guide-lines as you can see from this.

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