Some practical thoughts on number of repetitions


There is no doubt that lifting weights is becoming increasingly popular among wide population. There are some details that matter, althought almost nobody is thinking about them. For example, I have always been wondered if lifting to failure gives some special benefits or just makes your system more fatigued… Or, people have been promoting the idea that low reps were ideal for strength development, moderate reps (somewhere between 6-8 reps on the low end, and 12 to 15 on the high end) were best for building muscle, and high reps were best for building strength endurance, etc. Is this really true? Well, to some extent YES! Let’s discuss a bit…

Research has shown that when training with the same number of sets to failure, the rep range (as determined by the weight on the bar) does not matter. Yet, there are quite large differences in the volume load (sets x reps x weight) and time under tension between sets done with 8,10 and 12 reps to failure. This clearly showes that neither volume load (sets x reps x weight) nor time under tension are directly related to the amount of muscle growth that is stimulated by a strength training workout. The dosage of mechanical tension on individual muscle fibers determines hypertrophy (in other words, tension on the muscle is the major signaler for growth), so the last 5 reps of a set to failure are probably the ones that stimulate hypertrophy (by Chris Beardsley). Of course, there is more to say about those extra details (muscle damage, metabolic stress / time under tension, motor units recruitment, ROM, tr. volume, mind-muscle connection) but that’s for another topic… Theoretically, you can do your sets 2-3 reps short of failure (limiting peripheral and CNS fatigue) in order to do more sets (and therefore more “effective reps” in the same workout). But it depends on your available time, and your own tolerance to fatigue and failure (at least). It’s not that simple…

During a set or workout of multiple sets of a single strength training exercise, fatigue accumulates. When training at a closer proximity to muscular failure, the accumulated fatigue is even greater – which makes sense. And fatigue is also greater when training in higher rep ranges. Indeed, training closer to failure does cause greater fatigue than training with a couple of reps in reserve (RIR). However, this effect is very specific to the rep range that is used. Training with heavy loads involves far less fatigue (both during and after a session) than training with moderate or light loads (if going to failure or close to, with normal tempo). In fact, one research showed that the benefits of training with 2 RIR are actually completely removed if we use a 10-12RM load instead of a 5RM load for the workout. We will definitely experience more fatigue (not a good thing) when training with higher reps and with closer proximity to failure. So, you can go to failure with heavy loads (the weight you can lift up to 5 times) since it involves lower fatigue (but not if you lift with 413 tempo i.e. – which can even give you fatigue and hypertrophy similar to higher reps most probably). As we said (some researchers), you can also go to failure if training with 10-12RM since there are no significant benefits stopping 2 RIR in terms of fatigue. But wait, there actually might be a benefit considering less CNS fatigue e.g. with most people in this case – so everything is individual… Also, I don’t think hypertrophy stimulus will be MUCH better if we do all the 12 reps, and it’s a big question if going to failure with higher reps will recruit all the motor units because of the CNS fatigue (maybe only during the first, or two sets when fatigue isn’t accumulated yet). MORE ON THIS BELOW… So, I would always consider finishing sets with 1-2 reps in reserve (short of the failure) for athletes at least (in the end, it all depends on the main goals, therefore choices should be simple and smart – low risk & high reward). It’s mentally easier as well. Of course, max strength development (up to 5 reps per set, normal tempo) should be always done to failure because it doesn’t cause significant fatigue (if you want to be sure though, you can do 1 RIR – all the high-threshold motor units will be probably recruited/trained anyways, unless you believe that only the unilateral max lifts can recruit all the m. units because of the “bilateral deficit” – characterized by a reduction in the amount of force from a single limb during maximal bilateral actions…, also, how difficult is to recruit all the m. fibers of one muscle depends on the muscle itself as well – i.e. it’s much easier to recruit all of them when training biceps, than quads…). When it comes to 12+ reps, take the very similar philosophy to the “10-12RM” one (even more and sooner CNS fatigue in this case though). All of these is why the method where you decrease number of reps from set to set (while increasing load) “kills 2 birds with 1 stone” – hypertrophy & max strength (plus, a bit higher rep range during the first set “wakes up” many athletes very well for later much heavier loads). Of course, there is no max effect on both when it comes to this method, but you can use it if needed.

Some studies showed that, when it comes to untrained lifters, training to failure might be more effective per set (for hypertrophy), but it can give you more fatigue if doing more sets, and that fatigue can be detrimental to hypertrophy. But, anyways, if you are doing only 3 sets (let’s say 10 RM), it will be probably more beneficial if you go to failure than stopping shy of failure. But, when it comes to trained lifters, most studies showed that lifting to failure will NOT be more effective for hypertrophy (it matters to some degree though, but it’s not statistically significant). This is great, you can actually do a bit more volume (sets) because you will not be that fatigued (which is great for hypertrophy long-term).  

Remember one thing, in a short-term, intensity is the most important training variable for strength gains (up to 5 reps, 2-3-4 sets per exercise i.e.), but over the longer term – training volume plays progressively larger role (it depends on many things though… i.e. if an athlete doesn’t need much hypertrophy because there is no contact with opponents among other things, then we need to pay more attention to max strength training – it will make more benefits from the performance, injury reduction and recovery standpoint, but still we need to have a short hypertrophy phase in the beggining – off season). Training volume is very important for hypertrophy (4-6 sets of 8-15 reps per exercise i.e.). If you solely do high-intensity-low-volume stuff, you will make strength gains pretty quickly (which is good if one is relatively ready and the competition is very close), but you probably won’t develop enough muscle mass to keep making solid progress over the years. All in all, long story short, that’s why volume is more important if you are far away from competition, and intensity closer to comp. And, everything depend on your goal(s).

Some people take it to the extreme, and assume that any muscle growth outside of the “hypertrophy range” will be minimal or nonexistent. Other people will assent to the idea that you can still grow a bit with low-rep or high-rep training, but that your results will still be notably better if you stick to the “hypertrophy range.” Sure, you may be able to build a little muscle doing heavy sets of 3 or 20+ rep “pump sets,” but you’d grow more if you stayed in the hypertrophy range. Hmm, wait a minute, many people think that high reps are for toning, but some NEWER papers showed that they build just as much muscle as low reps if you push your sets close to the failure. With that said, long story short, pushing too many sets to failure will likely hinder your muscle-building progress. It’s definitely ok to go to failure, but not with every single set (12-20 sets per WEEK, per muscle group, is something that experienced lifters found as an optimal …maybe even less if you go high reps often).

The assumptions about lower reps/higher weights building more strength and higher rep/lower weights building more strength endurance have largely been validated. You can still gain strength with light weights/high reps and moderate weight/moderate reps, but strength gains are generally better with heavy, low-rep training. Conversely, you can build absolute muscular endurance (how many times you can move a set load, regardless of your 1RM) with low rep and moderate rep training, but you can build a lot more with high rep training, and high rep training is generally the only way to improve relative muscular endurance (how many times you can lift a certain percentage of your 1RM).

The “hypertrophy range” of roughly 6-15 reps per set may produce slightly better results per unit of time invested than low rep and high rep work. However, on the whole, the advantage you get from working in the hypertrophy range isn’t nearly as big as people seem to think; maybe a ~10-15% advantage per unit of effort invested at most.

“You can absolutely grow effectively when training with low reps and high reps. In fact, mechanistic  work has shown that although different rep ranges trigger similar elevations in protein synthesis, the signaling pathways activated to produce that growth response are actually somewhat different. You’re probably missing out on some growth if you confine yourself to a single rep range, even the “hypertrophy range.” My assumption is that individual signaling pathways would habituate to a single stimulus faster than multiple signaling pathways would habituate to slightly different stimuli. Due to the sheer amount of variability we’re looking at, both within studies and between studies, it’s probably not wise to assume that a single rep range will be the best for everyone. Some people and some exercises just seem to do better with higher reps or lower reps. I think instead of asking yourself, “Is this rep range better than this other rep range in some objective physiological sense?” you’re better off asking yourself, “What allows me to get in the most high quality sets during each session and during each week?” High quality sets refer to those that employ exercises that are likely going to be limited by the muscle you’re trying to train, through the longest range of motion you can maintain with safe form, taken within 2-3 reps of failure, and performed when you’re adequately recovered from your previous set (generally around 1.5-2 minutes of rest for isolation lifts, and 3-5+ minutes for heavy compound lifts).” – Greg Nuckols

For some people, heavy sets of 3-5 reps will – for lack of a better term – “burn out their CNS”, meaning that after a couple of challenging sets, they just feel fried and the rest of their workout suffers. I know, we have mentioned previously that CNS fatigue is not high after heavy load / low rep lifts, but there are some people who will experience it way more than others. So, again, everything is individual – and personal experience is key!

For other people, sets of 12-15+ reps will just crush them metabolically, especially for exercises like squats and deadlifts, meaning they can’t get in much high quality work after a couple of hard sets. As Greg N. says, maximizing hard sets within a session is also why stopping 2-3 reps shy of failure – especially on heavy compound lifts – is generally a good idea; a set to failure generally takes more out of you than a set stopped a bit earlier and limits how much more quality work you can handle. Also, don’t forget that velocity-based training studies have found that training closer to muscular failure impairs gains in high-velocity strength. Training with higher volumes probably have the same effect. In general, higher volumes are good for gains and not bad for strength, but low volumes are best for high-velocity strength.

‘Essentially, I think people have gotten the cause and effect mixed up: It’s not that there’s something magical about the “hypertrophy range” that makes it meaningfully better than other intensity ranges when other training variables are controlled for. It’s that simply being able to do more hard training tends to produce better results, and most people tend to be able to do the most hard training when they do the majority of their work in that intensity range.” – Greg Nuckols

With that in mind, your goal should be to find the rep range for each lift that allows you to get the most high-quality, hard work in.

I found one very interesting statement few years ago: During a single set to muscular failure, there are likely 5 stimulating reps. These reps are the ones that contribute to gains in muscular size. It seems that the volume that causes hypertrophy is not the total number of reps in a set. It is only those final reps before muscular failure when motor unit recruitment levels are high enough to allow high-threshold motor units to be recruited. WHEN TRAINING FOR HYPERTROPHY, volume is not the number of sets or raps that you do. It is the number of stimulating reps that you do. These are not the same thing! A program can involve a very high number of sets and reps, but if each set is done with a large number of reps in reserve, the stimulating volume can be very small.” – Chris Beardsley

But, the idea that the last 5 reps before failure are “effective reps,” and therefore the ones that REALLY matter for hypertrophy, doesn’t actually have all that much experimental support.

Chris also claims that, when training with multiple sets to failure, we achieve the same hypertrophy regardless of the weight on the bar. This is because only the last 5 reps of a set trigger growth. These stimulating reps are where recruitment is high (all fibers are working) and bar speeds are slow (tension is high).

There are two primary reasons one should expect the last 5 reps before concentric failure to be the ones that really matter for hypertrophy:

  1. Around 5 reps from failure is approximately the point where full motor unit recruitment occurs.
  2. Near failure, when shortening velocities are low, each recruited fiber is experiencing more mechanical tension (force), and is thus receiving a larger stimulus to grow.

Since 85-87% of 1RM is approximately a 5RM load for most people, it’s thus believed that you recruit basically all motor units from the very first rep when training with 5RM loads, or during the last 5 reps during a set to failure. The second reason I’ve seen put forth for why the last 5 reps are the ones that really matter comes from research showing that muscle EMG (electrical activity, which should be roughly associated with fiber recruitment and discharge rate) increases early in a set, and plateaus at a high level approximately 3-5 reps before failure…

But, we simply can’t get the same (or similar) amount of muscle growth when doing 5 reps (if done with “normal” tempo), compared to reps within the “hypertrophy range”. Tempo is very important (e.g. if the same number of sets done, we can get similar or even greater hypertrophy by doing 5 but very slow reps, then by doing 12 faster reps that are not too close to failure). But remember, Christian Thibaudeau says that, if we are increasing time under load by increasing duration of the eccentric phase or adding isometric actions in a set, it decreases the amount of growth (hypertrophy) you can stimulate because you will use lighter weights and will not be able to cause as much mechanical loading, or muscle damage, or mTOR activation, however by using eccentric-isometric method you will improve movement control, learn the movement skill (optimizing movement), improve muscle-mind connection… It has its purpose, but it’s not the best way to train for hypertrophy. So, don’t worry too much about time under tension when performing big compound movements (but it could be very useful for isolation movements if we talk about hypertrophy…). Number of reps is a variable that will have way stronger impact on muscle growth, in his opinion.

Last but not least, one good study showed that, if we do our sets between 40-80% of 1RM (if training to failure or close to, 1-3 RIR), hypertrophy is similar (if done with same number of sets, if we do higher % of 1RM we probably need a bit more sets to reach the same level of hypertrophy as if we do more reps but less sets). So number of reps doesn’t matter that much as long as we do hard sets (but, as we saw, volume does matter a lot – …I would say 3-6 sets per exercise is plenty, 3-5 times a week). Everything below 25% of 1RM (even if going to failure) will give quite a bit less muscular growth. All in all, hard sets between 30-80~85% of 1RM is the way to go when we talk about hypertrophy. Everything below 30% and above 85% approximately gives you a bit lower hypertrophy per set (gradually). But anyways, who wants to train at 30% of 1RM with so many reps?! Maybe single-joint moves sometimes (i.e. biceps curls), but if we are talking about big compounds – it’s not fun at all. We, of course, still need to change ranges/reps in order to reach the full growth potential. When we talk about strength (max) development, it needs to be hard sets for sure (to failure, or 1-2 RIR), but load needs to be 75%+ for maximum effect. And, those sets need to be high quality as well (first 5 sets are of the highest quality in most experiences, whether you do 3 or 5-6 reps per set – the more reps and sets we do the quality decreases in most cases).

Ok, we can discuss this very interesting topic forever, but I bet you got the gist. There are many parts of the topic to think about… Your welcome!

PS: One practical question for the end: Do you get larger strength gains per set from training closer to failure? Can you maximize strength gains from being far from failure? What I have heard from Greg N. is that strength gains are pretty similar (or no significant difference) whether or not sets are taken to failure. Some studies showed a bit more strength gains when you stop further away from failure (possibly because of the CNS fatigue when going to failure, among other things). For instance, if your main goal is strength development, if you do a set of 5 reps (around 85-87% 1RM), you will get maybe even better results if you do only 2-3 reps (max effort “speed”). If you’re not too worried about growth at the moment (but want to build strength short-term, and limited), stay a bit further away from failure. But, if you want more strength (powerlifting…), you need to build muscle prior or along with that (so, everything depends on your goals). Also, people who struggle recovering from strength work they do – for any reason (when you go closer to failure), short to moderate term they will get solid strength effects by lifting far from failure (less stressful). If you topically go 1-2 reps short of failure, but have stressful life and not recovering well, just cut 1-2 reps more from the same load and you will get the same (or very similar) strength gains, while making your workouts much easier and potentially recovering better (you will not grow much from that, but at least in terms of strength effects, it should work pretty well short to moderate term – this is ideal for athletes, especially when closer to competition). Again, this is a great strategy for gaining strength short to moderate term.

For the love of movement,