Jun 2012 04
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The optimal number of sets one should perform in a weight training routine is the subject of often heated debate. Proponents of ‘heavy duty’ or ‘HIT’ training insist that one set per exercise, performed to momentary muscular failure, is all that’s needed to trigger maximal increases in strength and growth.

While the heavy duty/HIT advocates are often quite vocal and insistent, the scientific evidence does not back their claims.

One For You, Three For Me

Most studies looking at this topic have compared one set of an exercise with 3 sets. While not all studies detected differences, overall the three set regimens produced superior results. A 2009 review of the research by James Krieger, published in the Journal of Strength and Conditioning Research, found that 2 to 3 sets per exercise were associated with 46% greater strength gains than 1 set, in both trained and untrained subjects[1].

The effect of even higher numbers of sets is less clear; 4–6 sets resulted in only 13% greater gains than 2–3 sets. Before you write higher set counts off as largely a waste of time, realize that this figure was derived from very limited data[2]. A mere 2 studies included in the review incorporated 4 or more sets per exercise. For some reason, exercise scientists repeatedly choose 3 sets as the comparison point in these studies, even though real world bodybuilding and strength training routines frequently utilize much higher set counts.

Thankfully that’s starting to change. A year ago I reported on a study in which Terzis and colleagues compared workouts utilizing 1, 3 and 5 sets of 6 reps[3]. They examined post workout changes in anabolic signalling proteins, and found the activity of these proteins to be higher after that 3-set routine compared to after the 1-set routine, and to be even higher again after the 5-set routine.

However, this was a short-term study that only examined acute changes in anabolic markers after a single workout; it does not tell us what would happen in terms of actual muscle growth and strength gains if the workouts were continued longer term. Would these acute changes in anabolic signalling proteins caused by higher set counts translate into real world increases in strength and hypertrophy over the longer term?

According to new research, the answer is yes.

One vs Four vs Eight Sets. And the Winner is…

A recent joint study by Aussie and Kiwi researchers compared the effect of one set of squats performed twice a week, with 4 and 8 sets also performed bi-weekly[4].

The researchers took healthy men (mean age 28) who had been weight training twice a week or more for at least the last 2 years, then randomized them to 3 different groups. In order to achieve some kind of standardized baseline, all groups performed the same routine for the first 2 weeks (a 3-way split routine with 4 sets of six exercises per session, using 6–12 reps).

After this ‘washout’ phase, the participants started their assigned routines. The only lower body exercise was the barbell squat, which one group performed for 1 set twice a week, while the other groups squatted for either 4 or 8 sets twice a week.

All groups used 80% of their 1-rep max on the squat, and performed the lift to momentary muscular failure (ie, the point at which performing another repetition in good form would not be possible). The multiple set groups rested 3 minutes in between each set of squats.

The average number of reps per set of squats performed by the 1, 4 and 8 set groups was 10.9, 7.7 and 7, respectively (average rep counts for the initial set were 10.9, 7 9.0 and 8.2, respectively).

Prior to beginning their working working set/s of squats, a warm-up set of 10 bodyweight reps was allowed, followed by a 10 rep set at 50% 1RM, then single repetitions at 60 and 70% 1RM.

As for the upper body, all participants followed the same routine, irrespective of the number of squat sets they were assigned to perform. A 2-way split program was used (A program: chest-shoulders-arms, B program: back and squat training), so that each muscle group was trained twice weekly.

This phase of the study lasted six weeks, and was then followed by a four week ‘peaking’ phase in which all participants once again performed the same program. This program combined low repetition, high load resistance exercise movements (4 exercises per session, 4–12 RM training intensity), with high intensity ballistic exercise movements (two exercises per session of either jump squat, bench press throw, dumb-bell snatch, barbell push-press). Four sessions per week were performed during this period, with each muscle group trained twice weekly. All participants performed the same squat prescription during this phase, with a 3 set x 4-RM prescription.

Dietary records indicated no change in the participant’s usual diets during the course of the study.

Body mass, fat mass, and 1RM squat were tested at the start of the 6-week phase, at weeks 3 and 6 of this phase, and at week 10 (the end of the 4 week consolidation phase).

So…What Happened?

At the end of the 6 week phase, the single set group had increased their 1RM squat by a mean 16.5 kilograms. Little additional gain was made during the subsequent 4-week consolidation phase (+0.9kg). Body mass increased over the 10 weeks by a statistically non-significant 0.5%, while fat mass decreased by a significant 2.0%.

The four set group increased the 1RM squat by a mean 20.9kg during the 6-week phase, and a further negligible 0.9kg during the 4-week peaking phase. Body mass decreased by a non-significant 0.5% and fat mass decreased by a significant 1.8%.

And the eight-set group?

They increased their mean 1RM in the squat by a mighty 32kg over the first 6 weeks, and a further 5kg during the following consolidation phase. Bodyweight increased by a statistically significant 1.5% while fat mass decreased by a significant 1.6%.

There are a few interesting findings to arise from this study. The most obvious is that, in males still on the right side of 30 and with previous weight training experience, a six week routine incorporating 8 sets of squats to failure produced far greater strength gains than a routine featuring only 1 set to failure.

The changes in body mass were minimal, with only the 8-set group adding any significant amount of bodyweight. In the face of accompanying fat loss, we can safely assume that this extra weight was lean mass (i.e muscle tissue, glycogen, etc). Keep in mind that for normal weight individuals wishing to achieve substantial increases in muscular bodyweight, a significant calorie surplus is essential. In this study, however, the participants kept eating their normal diet, which would automatically curtail any potential muscular bodyweight gains. Had the subjects been instructed to eat a minimum of 500 extra calories per day, much larger increases in lean mass would have occurred.

High vs Medium vs Low Responders

Another thing this study looked at is the percentage of low, medium and high responders in the study. High responders (n = 13) increased their squat strength by 29.4% compared to 14.3% for medium responders (n = 6), and 2.6% for low responders (n = 13). There was a proportionately higher number of low-responders in the single set group, which may simply have been an artefact of poorer strength gains produced by the single set routine (the other possibility is that, during randomization, a higher number of genetically-determined low responders were by chance assigned to the 1-set group, a possibility that while unlikely cannot be conclusively confirmed or refuted as the obtainment of genetic data was not a part of the study protocol). As this was a parallel-group trial and not a crossover study, we don't know whether more of the low responders would have become high responders on the multiple set routines.

“Nonetheless,” as the researchers stated, “that the numbers are so clearly skewed to associate high volumes with responsiveness lends some weight to the argument that regardless of categorical variables, high training volumes are preferred in order to develop strength.”

The other interesting observation is how little strength gain occurred during the consolidation phase. After a period of intense high volume training, a ‘deload’ phase consisting of lower volume and/or intensity is essential to consolidate one’s gains. Otherwise, one faces the very likely possibility they will sink into overtraining, suffer burn out, and unravel much of the gains achieved during the high volume phase. Properly designed deloads can not only consolidate previous gains but produce supercompensation, in which further gains are achieved as the body regroups and 'peaks' after the high volume work.

In this study, the 4-week peaking program prescribed after the 6-week randomized training period was only effective for high responding participants, regardless of the squat protocol they followed during the prior six weeks. Exactly why this was so is not clear.

I Feel the Need, the Need for Starting Speed

One last finding of interest was that, after the 10-week training routine, all participants, irrespective of their assigned squat volume, experienced declines in the rate of force development during the early phases of muscular contraction as measured on an isokinetic leg extension device. Theoretically, this would mean slower contractions and possibly poorer performance in activities requiring quick, explosive muscle contractions.

However, before all you power athletes log into eBay to unload your gym equipment, keep in mind that the leg extension is an isolation movement that measures activity of the thigh muscles, whereas the squat develops not only the thighs but also the buttocks, lower back, and hamstrings. Real life performance effects of the squat out on the field might be significantly different from those observed on a dynamometer that utilizes the isolated leg extension movement.

That said, the finding is still noteworthy and can’t be dismissed out of hand. The researchers speculated that low-level fatigue was the most feasible explanation. Whether a non-failure routine or a routine that also included plyometric or lighter explosive squatting movements during the initial six-week phase would have produced different results is something that future research will have to answer.

In Summary

This study adds to the significant volume of research showing that multiple sets are superior for strength gains than single sets. The further gains seen on the 8-set routine compared to the 4-set routine suggest that in previous studies where no significant differences were seen between 1- and 3-set routines, the relatively small difference in volume may have been insufficient to elicit any significant difference in strength gains.

As for muscle hypertrophy, there is a dire shortage of studies in which participants are assigned not just to differing weight routines but also instructed to consume a calorie surplus. Studies of this type are desperately needed to help ascertain optimal training protocols for budding bodybuilders and those looking to gain additional muscle for sport/the beach/the bedroom.

One more thing I'd like to add: For any fellow 'early adopter' types that want to incorporate this information into their own routines, my advice would be not to start doing 8 sets to failure of every single exercise you currently perform. Pick a key exercise for the major bodyparts, such as squats, bench, rows/chins/pulldowns, hang cleans/power cleans, and work it for 8 sets. Run everything else or 3-4 sets and take it from there, otherwise you'll have a new companion called Ova Tré Ning. After doing your first 8 sets of squats to failure, I'm sure most of you will know where I'm coming from...

Also, this study tells us nothing about training to failure as compared to non-failure, as all groups performed their work set/s to failure. Older lifters, individuals subject to significant life stressors, or those with symptoms of what is popularly referred to as "adrenal fatigue", should seriously consider stopping 1 or 2 reps short of true failure.


  1. Krieger JW. Single versus multiple sets of resistance exercise: A meta-regression.  Journal of Strength and Conditioning Research, 2009; 23 (6): 1890–1901.
  2. Krieger J. Determining Appropriate Set Volume for Resistance Exercise. Strength and Conditioning Journal, 2010; 32 (3): 30-32.
  3.  Terzis G, et al. The degree of p70S6k and S6 phosphorylation in human skeletal muscle in response to resistance exercise depends on the training volume. European Journal of Applied Physiology, 2010; 110: 835–843.
  4. Marshall PWM, et al. Strength and neuromuscular adaptation following one, four, and eight sets of high intensity resistance exercise in trained males. European Journal of Applied Physiology, 2011; 111: 3007–3016.


Anthony Colpo is an independent researcher, physical conditioning specialist, and author of the groundbreaking books The Fat Loss Bible, The Great Cholesterol Con and Whole Grains, Empty Promises.

Copyright © Anthony Colpo.

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