Single set versus Multiple Sets – new research

There has been an ongoing debate in the strength training and bodybuilding communities for about 40 years as to whether a single set of an exercise is superior for building size and strength than training with multiple sets.  The idea that a single set of an exercise might be more effective than traditional multiple set training was first popularized in the 1970s by Arthur Jones, inventor of Nautilus strength training equipment.

Based on his training observations, Jones believed that a single set per exercise taken to the point of failure- a training method that is commonly known as high intensity training (HIT)- was the most effective type of training for improving both strength and size.  In a series of published bulletins widely circulated throughout the strength and bodybuilding communities, Jones made his case for the superiority of single set training, sparking heated debate on the issue that continues to this day.

The debate drew the attention of exercise physiologists around the world, resulting in a growing body of research data examining the issue.  However, despite an abundance of research studies physiologists were not able to resolve the issue.  The main problem was that the research was equivocal; some studies supported the idea that a single set was more effective than multiple sets, other studies found multiple sets produced greater increases in strength and size, but most studies found no statistical difference in results between the two training methods.  In short, there was no consensus in the research.

In general most research indicates that multiple sets tend to produce somewhat larger increases in strength and size.  However, the issue is that the difference in results between the two has not been large enough to definitively say that multiple sets are superior.  On average multiple sets produce a few percentage points greater increase in strength and size, usually in the range of 2-10%, but this difference has not been large enough to be statistically significant (statistical significance is important to show that the results are not just a matter of chance).

With research unable to declare a clear winner the debate continued unabated.  Despite the lack of consensus the physiological community generally accepted multiple sets to be superior to a single set, which drew some very vocal and deserved criticism from a few scientists.

In response to these critics a number of “meta-analyses” have been conducted by researchers in recent years to see if the conflict could be resolved.  A meta-analysis is essentially a study of studies.  It is a way of analyzing the results of multiple studies on the same research hypothesis to see what can be learned by looking at the entire body of research data as a whole versus the examining the results from individual studies.  A meta-analysis can often more powerfully estimate the “effect size”, the true difference in results, in comparison to the smaller “effect size” of a single study.  Measuring “statistical significance” is different than measuring “effect size”.  The advantage of measuring effect size via a meta-analysis is that it may reveal actual differences that were missed by examining the statistical significance of the results of the individual studies comprising the meta-analysis.

Let’s have a look at these meta-analyses and see if they have finally put to rest the whole single set versus multiple set debate.

Strength Studies

The first meta-analysis was conducted by Rhea et al (4) in 2002.  Examining 16 studies Rhea reported that 3-set training produced superior results to 1-set training.  In 2003 Rhea et al (5) conducted another meta-analysis, this time of 140 published studies, and concluded that 4-sets produced maximum strength gains in both trained and untrained subjects.  Both of these studies received some criticism due to the criteria Rhea used for study inclusion and also for his statistical analysis methods.

A third meta-analysis conducted in 2004 by Wolfe et al (6) of 16 studies found multiple sets to be superior to a single set in trained subjects and in programs lasting 17 to 40 weeks.  As in both Rhea’s meta-analyses, Wolfe’s study received some criticism for his statistical analysis methods.

Aware of the criticism of the previous three analyses, Kreiger (3) conducted a fourth meta-analysis in 2009 specifically designed to improve upon the limitations of the previous studies.  He examined 14 studies with 92 effect sizes measured across 30 groups of subjects comparing 1-set, 2-3 sets, and 4-6 sets.  He found that 2-3 sets produced 46% greater increases in strength than 1 set in both trained and untrained subjects.  Interestingly, he also found no difference in results between 2-3 sets and 4-6 sets.  Performing more than 3 sets did not produce a greater increase in strength.  Kreiger’s study strengthens the findings of both of Rhea’s previous studies.  There were some differences between Wolfe’s findings and Kreiger’s findings in terms of the effect of volume of training but Kreiger’s study also strengthened Wolfe’s finding that multiple sets produce superior results to a single set.  Finally, a 2010 meta-analysis of 72 studies by Frohlich et al (1) found single set training to be the equal of multiple set training for short training periods but multi-set training to be superior over longer periods of training.

In summary, there is now a consensus in the research literature supporting the idea that multiple sets are superior to single set training for increasing muscular strength.

Size Analysis

All of the meta-analyses cited above examined differences in strength gains; none examined the issue as to whether single or multiple-set training elicited greater muscle size gains.  Increases in strength are caused by both neural and hypertrophic changes and it is possible that the superiority of multiple sets for increasing strength might be due to a greater neural effect and not hypertrophy.  It is possible that multiple sets might be superior for increasing strength but not size so this issue needed to be resolved also.

In 2010 Kreiger (2) addressed this topic with another meta-analysis designed to determine if multiple set training elicited greater muscle hypertrophy compared to single set training.  Examining 55 effect sizes across 19 groups in 8 studies he found that multiple sets produced 40% higher increases in muscle hypertrophy regardless of the training status of the subjects or the length of the training program.  Kreiger also concluded that the 46% greater increase in strength from multiple sets revealed in his earlier meta-analysis was largely due to greater hypertrophy and not neural factors.

Interestingly, while Kreiger found no significant difference in hypertrophy from 2-3 sets or 4-6 sets he did find a trend for greater hypertrophy with 4 or more sets.  One weakness of his analysis was a limited number of studies that utilized 4 or more sets so he stated that no definitive conclusion could be reached as to whether 4 or more sets was superior to 2-3 sets for inducing muscle growth.

Summary

The debate as to the superiority of single versus multiple set training has been on-going for around 40 years.  High intensity training (HIT), originally popularized by Arthur Jones in the 1970s, promotes the idea that single set training is superior to traditional multi-set training for improving both strength and size.  Until now research on this topic has been equivocal and unable to resolve the dispute.  However, six recent meta-analyses have confirmed that multiple set training produces greater increases in both strength and size than single set training in both trained and untrained subjects.

References:

 1.       Frohlich M, Emrich E, Shmidtbleicher D., Outcome effects of single-set versus multiple-set training- an advanced replication study. Res Sports Med. 2010 Jul;18(3): 157-75

 2.       Kreiger JW., Single vs. multiple sets of resistance exercise for muscle hypertrophy: a meta-analysis. J Strength Cond Res. 2010 Apr; 24(4): 1150-9

 3.       Kreiger JW., Single versus multiple sets of resistance exercise: a meta-regression. J Strength Cond Res. 2009 Sep; 23(6): 1890-901.

 4.       Rhea, MR, Alvar, BA, and Burkett, LN. Single versus multiple sets for strength: a meta-analysis to address the controversy. Res Q Exerc Sport 73: 485–488, 2002.

 5.       Rhea, MR, Alvar, BA, Burkett, LN, and Ball, SD. A meta-analysis to determine the dose response for strength development. Med Sci Sports Exerc 35: 456–464, 2003.

 6.       Wolfe, BL, Lemura, LM, and Cole, PJ. Quantitative analysis of single- vs. multiple set programs in resistance training. J Strength Cond Res 18: 35–47, 2004.

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