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When working out with weights, what is the impact of the trade-off between

  • the amount of weights used
  • the number of times an exercise is repeated

For example, I can perform an exercise 3 sets x 10 reps with 20kg weights but only 3 sets x 7 reps with 25kg weights. What will be the difference of these two exercises on the body?

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1 Answers1

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Your goals and your current level of progress determine the number of sets and reps.

Possible Goals

Training for strength, power, endurance and hypertrophy all require a different number of sets and reps:

  • Strength (how much weight your muscle can move) is best developed by lifting as much weight as possible. This is probably best achieved with 5 or less reps. Strength is expressed in how much you can lift one time, so the closer you train to 1 rep at a time, the more specific you are training for strength.
  • Power (how much your muscle can move quickly) is best developed by moving heavy weights very fast. This is best achieved with very few reps, something like 2 or 3 in a set, but you have to use slightly less weight so that you can move it faster.
  • Endurance (how long your muscle can keep doing its job) is best developed by lifting a weight many times, which requires many, many more reps: at least 15. You'll have to use a lot less weight in order for this to be possible.
  • Hypertrophy (how big your muscles are) is best developed by achieving momentary muscular failure, and with overall training volume. Moderate weight works best for this purpose, since it is heavy enough to quickly make one unable to lift it, but not so heavy that failure to lift is dangerous. Most people use 6-12 reps for this purpose, but there may or may not be anything special about this range. Multiple sets and exercises are useful for achieving high total workout volume.

This is well explained by a chart in the article I linked to:

Sets, reps, rest periods for different goals

Three sets of 7 at 25kg will demand and develop more strength than three sets of 10 at 20kg would. The sets of 10 would promote greater hypertrophy and require more strength-endurance and conditioning. The difference is not going to be terribly significant, however, since 7 and 10 aren't too far apart.

Doing fewer reps with heavier weights requires and develops more strength and less conditioning than more reps with somewhat lighter weights. Doing more reps with slightly lighter weights may, in some circumstances, for some exercises, produce more hypertrophy (mass gain). Fewer heavier reps is better for strength; more reps (but still as heavy as possible) is better for size.

Though the original on page 60 of Rippetoe & Kilgore's Practical Programming is better (the gradations from range to range are less stark) this chart from reddit does an excellent job explaining the effects of different rep schemes: Weight training repetitions table

Doing fewer repetitions with heavier weights builds strength most effectively. Doing more repetitions (circa 4 to 12), with weight that is still challenging, builds mass most efficiently. Doing more than 12 repetitions in a single set is generally best for endurance as opposed to strength. (See this answer for more information.) Does this mean that someone who is diligent with a 12-rep program can't get strong? Heck no! People get strong with 12-rep sets all the time. But if raw strength is their goal, they could probably achieve that goal faster with sets of, say, 3 or 6.

A novice generally does best with a focus on strength and some hypertrophy. Three sets of five or five sets of five are the two most common set/rep schemes. The weight must be heavy enough to make more than 5 sets very difficult.

Note that there is very little about these rep ranges in and of themselves that produces desired attributes. It is how these rep ranges relate to elements of training such as volume, intensity (that is, proximity to 1RM), and muscular exhaustion that determines the effects of training. Notice also that hypertrophy produces strength and power, and strength and endurance enable hypertrophy.

The following "map", from the Starting Strength site, explains the relationship of this volume-to-purpose relationship to sports. It refers to the three metabolic pathways: phosphagenic, glycolytic, and oxidative. The phosphagenic pathway is used when we do a very small number of reps in a set (3 or less, whereas higher-rep sets use the glycolytic pathway (approximately 4 to 12, though it depends on how vigorously one is working out). The oxidative pathway is for even higher rep ranges (e.g. 20), and is more commonly associated with longer duration, repetitive exercise like distance running or bicycling. It is explained in more detail in this article. sports-to-metabolic-pathway chart

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Dave Liepmann
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  • I continue to be amazed at your insightful and thorough answers. Well done @DaveLiepmann. Serious question though - are you on the Starting Strength franchise payroll? – Mike S Dec 11 '12 at 23:11
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    @MikeS Uh, no, I just found the book to do its job in a way that resonated with me. I plug other programs and authors, too, in the appropriate contexts--Kurz on exercise science, GreySkull LP for upper-body enthusiast novices, paleo/Weston A. Price diets, and so on. If Mark Sisson would write a to-the-letter "do this if you're a novice" workout program, I'd probably plug that more than SS. – Dave Liepmann Dec 11 '12 at 23:22
  • The 'effect scale' on the first image you listed doesn't make sense. Why is the grey in the center darker than the grey above it? – Parseltongue Aug 20 '13 at 20:57
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    Actually, following the Reddit link gives you a much higher resolution version of the same image, and everything makes sense now: http://i.imgur.com/UrF1U.png – Parseltongue Aug 20 '13 at 20:58
  • @DaveLiepmann, What if you want all? Strength + power + endurance? – Pacerier Jun 03 '15 at 21:43
  • @Pacerier Then train in multiple rep ranges, either in different mesocycles (month- or six-week-long period) or with weekly or daily undulating periodization (DUP). Or be more specific with your goals: if it's for sport, then train the sport plus supplemental work to train what the sport does not. – Dave Liepmann Jun 04 '15 at 09:25
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    I must say I don't really understand this chart from reddit. Almost all of the dark (= optimum) areas are in the 1-5 range, so why would anybody ever train anywhere within the 6-20 range (as bodybuilders do)? – s427 Mar 10 '16 at 11:56
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    @s427 A) if your goal is sarcoplasmic hypertrophy (that is, big muscles) or something else not served best by 1-5, B) if you have limitations on working in the 1-5 range, like you're using movements inappropriate for high-intensity/high-load work – Dave Liepmann Mar 10 '16 at 12:07
  • Thanks for your answer. B) makes sense, but A) is precisely what I don't understand, since (according to the graph) sarcoplasmic hypertrophy is not optimal in that range, but rather around 20 reps. Yet people training for mass almost always recommend the 8-12 range. – s427 Mar 11 '16 at 10:02
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    @s427 1) "the original [chart] on page 60 of Rippetoe & Kilgore's Practical Programming is better (the gradations from range to range are less stark)" 2) just like doing singles and doubles is optimal for strength but sets of 5 or more are used in strength programs to get the benefits of hypertrophy, working in in 8-12 provides benefits other than pure hypertrophy. – Dave Liepmann Mar 12 '16 at 19:32
  • You didn't mention anything about "Speed" goal, may I ask why? – Eido95 Jun 04 '16 at 15:51
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    @Eido95 For the purposes of this question I omitted speed training concerns since training for speed in the context of lifting weights is almost identical at this level of detail to training for power. A full speed training regimen would involve other techniques to achieve other attributes but isn't in scope here. – Dave Liepmann Jun 05 '16 at 20:02
  • Wow, where is that “the formula for getting fit” graphic done? – TylerDurden Jul 13 '23 at 17:53
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    @Seekinganswers as mentioned in the text, it's from the men's journal – Dave Liepmann Jul 13 '23 at 21:43