Muscle Factor Training A New Paradigm

Reblogged from

Muscle Factor Training

A New Paradigm

You may be familiar with the old adage – heavy weights / low reps build strength & size, light weights / high reps build endurance.  This belief about the effects that different numbers of repetition have on the body has been repeated for many, many years.  I started lifting weights in 1982 and it was accepted as truth at that time.  This belief is even accepted wisdom in the exercise physiology community.  The exercise physiology textbook in my library, published in 1996, states, “Performing an exercise between 3-RM (repetition maximum) and 12-RM provides the most effective number of repetitions for increasing muscular strength.”(1)  The bottom line is that there is little to no debate as to the effect different numbers of repetitions have on the body.  If you want to increase strength and size, heavy weights and low reps is the universally agreed upon prescription.

From a practical perspective this has resulted in most or all resistance training programs recommending heavy weights and low reps exclusively.  Basically every strength training or bodybuilding program recommends repetitions of 20 or less.  During 15 years of following popular strength training literature I can recall only 2 instances where reps higher than 20 have been discussed and in only one of those instances was it even seriously recommended as a viable training method.

In the first case, in the early 1980s or so a professional bodybuilder (Johnny Fuller, if my memory serves me correctly) revealed that he preferred to train using 32 repetitions for most or all of his exercises.  At the time this was used as an example of the recommendation that each trainee needs to find what works best for him/herself, but I don’t recall that the article recommended such high reps for anyone else.  Nor did any follow on articles I ever saw suggest that trainees might experiment with reps in that high range.

In the second case, Muscle and Fitness magazine ran a few articles in the late 1980s about 100 repetition training.  This series was run after one bodybuilder in particular revealed that he used 100 reps for brief training periods a few times a year.  After that series of articles, I don’t recall ever hearing about this type of training again.

So, while the adage says heavy weight/low reps build strength and light weights/high reps build endurance, I do not believe that high rep strength training is commonly used or seriously considered as a viable training method by most trainees or their coaches.  It isn’t commonly recommended to those who are most interested in increasing strength and/or size, nor does it seem to be a part of the serious endurance athletes training methods.

Since the adage says light weights / high reps building endurance, and increasing endurance is a goal of endurance athletes, I began wondering why high rep strength training was not commonly used by endurance athletes.  Even though the primary goal of endurance athletes is to improve endurance, heavy weight / low rep strength training is what is most often recommended to them.  The reason strength training is believed to be beneficial for endurance athletes is that it increases the amount of force produced during contraction, resulting in an increase in power output and, presumably, endurance performance.  What about the second part of the adage though?  The part that says light weights / high reps build endurance.  One of the muscle factors contributing to power output is fatigue resistance.  Increased resistance to fatigue is just another way of saying that the muscle’s endurance increased.  I reasoned that if high rep resistance training really did increase endurance then perhaps it might be a beneficial training method for endurance athletes.  With that thought in mind I started searching the available research to see what had been done on this topic.  I found some exciting and surprising research for us to review.  Let’s get to it.

Heavy weight/low rep vs. medium weight/medium rep vs. light weight/high rep

The first thing I wanted to know was whether research supported the belief that heavy weights / low reps build strength and that light weights / high reps build endurance.  After all it wouldn’t be the first time that someone discovered that conventional wisdom was not completely accurate.  I thought it best to be sure.

The classic research on this topic was conducted by Thomas DeLorme in 1945 (3).  DeLorme’s research indicated that heavy weights do indeed build strength while higher reps build endurance.  DeLorme is even credited with the axiom that heavy weights / low reps build strength and high reps / light weights build endurance.  Quite a few other research studies on this topic have supported DeLorme’s findings hence the reason it is now accepted as conventional wisdom.

This is not to say that DeLorme’s original axiom has gone unchallenged though.  Several research studies (4,5) that have found that the primary adaptation to either high or low reps is an increase in muscular strength.  So even though it is accepted today that heavy weights / low reps builds strength and light weights / high reps builds endurance the fact is that some research has challenged this belief, suggesting that high reps primarily build strength, not endurance and resulting in conflicting data on the topic.

In 1982 two researchers from the University of Kentucky set out to resolve this conflict (6).  Specifically, they wanted to determine the effects of three different resistance training protocols – heavy weights / low reps (6-8 reps), medium weight / medium reps (30-40 reps), and light weights / high reps (100-150 reps).

They recruited forty-three untrained, healthy subjects and trained them with the bench press exercise three times per week for nine weeks with one of three training protocols.  The low rep group performed 3 sets x 6-8 reps maximum, the medium rep group performed 2 sets x 30-40 reps maximum, and the high rep group performed 1 set x 100-150 rep maximum.  Resistance was adjusted as needed to ensure each subject stayed in the appropriate rep range through the training program.

Before training began each subject was tested for their individual 1 rep maximum (1-RM), relative endurance and absolute endurance.  Relative endurance was determined by the maximum number of bench press repetitions they could complete with 40% of their 1-RM and adjusted as 1-RM changed, while absolute endurance was measured by how many reps could be completed with 27.23 kilograms.

At the end of the study all subjects were tested again for maximum strength, relative endurance, and absolute endurance.  All three groups improved maximum strength and absolute endurance.  The heavy weight / low rep group decreased in relative endurance while the other two groups increased relative endurance significantly.  The results of this study are shown in table 1.

Table 1:  Percent changes in max strength, absolute endurance, and relative endurance following strength training at three distinct repetition ranges

Training Group

% Change in Max Strength

% Change in Absolute Endurance

% Change in Relative Endurance

Heavy weight /

low rep




Medium weight / medium rep




Light weight /

high rep




As can be seen from the data in table 1, the results of this study support DeLorme’s axiom.   Heavy weight / low reps do build strength, while light weights / high reps build endurance.  However, in contrast to DeLorme’s axiom, note that all 3 rep ranges resulted in increases in maximum strength.  And all 3 rep ranges resulted in increases in endurance, with the exception of the relative endurance of the low rep group.  So while low reps increase maximum strength more than do high reps and high reps increase endurance more than low reps the point is that resistance training significantly increases both strength and endurance.  The researchers commented on this same point.

“The reader should note, however, that with the exception of the relative endurance task for the high resistance low repetition group, all training protocols demonstrated significant improvements on each of the three criterion tests.”

Anderson and Kearney’s research went a long way to resolving the conflicting data on DeLorme’s axiom – heavy weights increase strength the most, high reps influence endurance the most, but all resistance training results in improvements in both strength and endurance.

In 1994 Stone and Coulter modeled a study after Anderson and Kearney’s study with the exception of using a less extreme rep range for the high rep group (7).  Stone and Coulter had their subjects perform either 3 x 6-8 reps, 2 x 15-20 reps, or 1 x 30-40 reps.  The results of this program supported the findings of Anderson and Kearney.  Strength and absolute endurance increased for all three groups.  The low rep group improved strength more than the other 2 groups and the high rep group improved endurance more than the lower rep groups.

The bottom line is that while DeLorme’s basic axiom is generally supported by this research, the fact is that resistance training results in improvements in both strength and endurance but to varying degrees depending on how many repetitions are performed.

What about alternating rep ranges?

The studies cited above have compared one rep range to another, high reps vs. low reps for example.  In every study researchers had subjects perform just one rep range and in each case heavy weights / low reps increased strength the most.  What the researchers never examined was how a program of multiple rep ranges compared to a program consisting of a single rep range.

In 2004 a group of researchers tackled this very question in a fascinating study of varying combinations of high and low rep training (8).  This group speculated that a combination type program that included both low and high reps would be more effective than a periodized program consisting of single repetition scheme during each training period or phase.

To test their hypothesis they recruited 17 untrained subjects, divided them into two groups, and then trained each group twice per week for 10 weeks.  Subjects were tested for maximum strength and muscular endurance pre- and post-training.  The first 6 weeks of training was designated as phase 1 and both groups trained exactly the same during this phase. Workouts consisted of two exercises (leg extensions & leg presses) for 3 sets x 10-15 reps.  At the end of this first phase of training there was no difference between the groups; both had significantly and equally improved strength and endurance.  This is not surprising since both groups trained exactly the same during phase 1.

During the final 4 weeks of the study, both groups conducted 5 sets x 3-5 reps of each exercise.  One group, the combi-type group, added a single set of 25-35 reps following their final low rep set.  At the end of the training program the combi-type group had increased their strength 58% more than did the other training group (14.7% vs. 9.3% respectively).  The results are displayed in table 2.

Table 2:  Set and rep ranges for 2 training phases and percent change in strength following phase 2.

Training Group

Phase 1 training

Phase 2 training

% Change in strength after phase 2

Strength type group

9 sets x 10-15 reps

5 sets x 3-5 reps

9.3 %

Combo type group

9 sets x 10-15 reps

5 sets x 3-5 reps,

1 set x 25-35 reps


In their discussion of these findings, the researchers wrote,

“This suggests that the combi-type regimen caused a larger increase in dynamic muscular strength than did the strength-type regimen when combined with the hypertrophy-type regimen in a periodized fashion… This effect appears to be inconsistent with the classical principle operating in resistance-exercise training, in which low-repetition protocols are used for muscular strength and low-intensity, high-repetition protocols are used for muscular endurance.  Sensible combinations of high- and low-intensity protocols may therefore be more important to optimize the strength adaptation to resistance training.”

There were also significant differences in endurance between the two groups.  During phase 1 both groups increased endurance with no significant difference in the percent change.  However, the combo type group’s endurance continued to increase during phase 2, while the strength type group’s endurance decreased 4.2%.  The results are displayed in table 3.

Table 3:  Percent change in endurance following each phase of training and total percent change in endurance.

Training Group

Change in endurance, phase 1

Change in endurance, phase 2

Total Change in Endurance

Strength type group

28.5 %

-4.7 %

24.3 %

Combo type group

20 %

18.8 %

38.2 %

In summary, this study found that a combination program consisting of heavy weights / low reps and light weight / high reps was more effective for improving both strength and endurance than a traditional periodized training program consisting of a single rep range during each training phase.  This is truly a fascinating finding.

What Does All This Mean?

What are we to make of all this data on low and high rep strength training?  Based on this data I suggest that the evidence supports that resistance training consisting of a combination of reps is superior to a more traditional lower-rep strength training program.  While I’d like to see more research on this topic this data is enticing enough that I strongly recommend giving a combination of low rep / high rep training serious consideration.

Personally, I adopted a combination high and low rep program in 2007.  At that time I had been strength training consistently for 25 years (I started in 1982) and had tried pretty much every training program that had come down the pipe.  Changing to a combination program was the single best change I’ve ever made in terms of increasing strength.  Despite being in my mid-40s and many years past my prime I was able to increase my strength to the level it had been at during my mid-20s.  Too bad I didn’t discover this 25 years earlier.

What explains the results of a combination program?  What physiologically is happening within the body that produces such large strength gains?  Why does the addition of high rep training – training that has been conventionally viewed as endurance training – to a traditional low rep program produce greater gains in strength than a low rep program only?  I pondered this question for about a year until I finally arrive at the muscle factor model as the physiological explanation.  I believe this new model for how muscles function during exercise and how they adapt to exercise explains why a combination program is superior to single rep range training.  Based on this I chose the term Muscle Factor Training to describe combination training.

If you would like to try muscle factor training I suggest starting with the following. In addition to the low rep training you are already doing, add:

  • one set of 20 reps (range of 17 – 23 reps)
  • one set of 40 reps (range of 35 – 45 reps)

For example, let’s say your current training program includes 4 x 8-10 reps in the bench press.  You would replace 2 of those low rep sets with 1 set of 20 reps and 1 set of 40 reps.  Your new bench press program would look like this:

  • 2 sets x 8-10 reps
  • 1 set x 20 reps
  • 1 set x 40 reps


The old adage is that heavy weights / low reps build strength while light weights / high reps build endurance and a review of the research shows that the adage is basically true.  However, while that adage is basically correct it does not reveal the complete picture.  Strength increases from reps as high as 150 but if you are only doing one rep range then lower reps increase strength the most.

A combination of both high and low reps – what I call Muscle Factor Training – has been shown to increase strength significantly more than a traditional low rep, periodized type training program.  For those who are most interested in maximizing muscular strength and size this finding is significant and should be seriously considered when designing a strength training program.


1.  Katch, Katch, McArdle, Exercise Physiology, Energy, Nutrition, and Human Performance, 1996, Williams & Wilkins, pg. 427

2.  Muscle Limit Performance, Muscle Contractility

3.  DeLorme, Thomas L., Restoration of muscle power by heavy resistance exercise, Journal of Bone and Joint Surgery, 1945, 27:645-667.

4.  Stull G, Clarke D., High-resistance, low-repetition training as a determiner of strength and fatigability, Research Quarterly, 41(2), 189-193

5.  Clarke D, Stull G., Endurance training as a determinant of strength and fatigability, Research Quarterly, 41(1), 19-26

6.  Anderson T, Kearney J., Effects of Three Resistance Training Programs on Muscular Strength and Absolute and Relative Endurance, Research Quarterly for Exercise and Sport, 1982, 53:1, 1-7.

7.  Stone WJ, Coulter SP., Strength/endurance effects from three resistance training protocols with women, J Strength Cond Res 8:231-234.

8.  Goto K, Nagasawa M, Yanagisawa O, Kizuka T, Ishii N, Takamatsu K., Muscular Adaptations to Combinations of High- and Low-Intensity Resistance Exercises, J Strength Cond Res, 2004, 18(4), 730-737.


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