Why a Pump Doesn’t Build Muscle

295 pound bench press

Nov 17 2016

What’s up guys? Tim from RazorStrength here, busting apart a training principle that has been propagated for far too long.

I’m sure you’ve seen the videos of “hard-core” bodybuilders (who to be fair are 100% jacked) who knock strength training and claim getting jacked is all about totally annihilating muscles when they train them.

“You don’t want to be doing heavy sets of 5s on the bench to grow”

“You need to cut that weight in half and do it for 20 reps to blow up your chest”

I’ve got to admit – it does sound good.

That they’re as jacked as they are because they put in crazy amounts of effort per session and curl till their biceps nearly explode. You watch them do some crazy squat drop-set and fall on the floor, and admit yes that does look hard – if I could do that surely I would be as big as them.

Reality check. Nope, that’s not even slightly true. Getting a pump (as good as it feels) is not the optimal method to build muscle.

You can use pump style training to grow, yes, but there is more to it than that. A massive body of research has proven that rep ranges are in-fact irrelevant in training volume controlled studies (more on training volume later), and that there is no extra benefit to performing higher rep, pump-inducing sets for increased size gains (Campos et al., 2002, Folland et al., 2002, Mitchell et al., 2012, Schoenfeld et al., 2014, & Van Roie et al. 2013).

If you’re interested in the research it’s all linked in the “References” section.

But why then do bodybuilders always preach high rep sets, massive amounts of time under tension, and skin-splitting pumps?

The problem with taking training advice from celebrity bodybuilders is the topic of another post. For today we’re just going to look at the science of it all.

You might be thinking, ok it might be possible, but surely it’s not optimal to train without ever getting a pump. More reps are more stimulus on the muscle right?

To look at this properly, we need to look at the determining factors of muscle hypertrophy (growth). When training for hypertrophy there are three main keys to worry about (Schoenfeld, 2010):

• Mechanical Tension
• Metabolic Stress
• Muscle Damage

Let’s dig into these in a bit more detail.

Mechanical Tension

This is quite simple. When you perform resistance training and lift weights, you are applying an external force to your joint, which your muscles resist. This resistance is mechanical tension – your muscles are working to resist the weight.

Essentially, the more tension you can put your muscles under, the more hypertrophy you will experience. That’s why 30lb dumbbells will grow your arms more than 15lb dumbbells.
So to increase mechanical tension, what can you do?

1. Use heavier weights
2. Increase the time under tension (slower reps, isometrics)

More on this in a bit.

Metabolic Stress

Secondly, we have metabolic stress. What is it? Essentially all it refers to is the reliance on anaerobic adenosine triphosphate (ATP) production in your working muscles. This leads to a build-up of metabolites and eventual fatigue.

Now if that confused the hell out of you, let me quickly explain it in simple terms.

Your body has three energy systems to produce something called ATP. ATP is the energy your muscles use, like fuel for your car. If you run out of fuel, your muscles fatigue and you can’t perform any more reps.

So back to the three energy systems, they function very similarly to gears in your car – they trade power for sustainability. You could be cruising along the highway in third gear – using a hell of a lot of gas and having to stop every 50 miles to refuel, but at the same time if someone tried to pass you – you sure as hell could put a stop to that.

Or you could be cruising in 5th or 6th gear and not have to stop for gas anywhere near as often – but that guy in his GTR is always going to zoom past you without competition.

That is exactly how your body’s energy systems work.

You could use your slowest energy system to provide you with a small amount of energy for hours on end (like a marathon runner), or you could use your fastest energy system to provide you with a very large amount of energy, but only for a very short time (like a powerlifter). This slow energy system is called the aerobic system, and we will disregard this for weight training – it really only applies for constant exercise lasting longer than 2-5 minutes.

When we’re lifting weights, the main two you’re using is your ATP-PC system and anaerobic glycolysis. The powerhouses.

Stick with me here.


The ATP-PC system is very powerful, but also has a very short duration. Essentially it uses something called phosphocreatine (which is stored in your muscles) to instantly resynthesize (create more) ATP in your muscles once you run out. The problem is, phosphocreatine is limited. You only have a small pool available in your muscles. Once you’ve used it all up, you fatigue.

Side note: This is why creatine works for most people, it gives you a larger pool of phosphocreatine to work with, so you can resynthesize more ATP and get more reps before you fatigue. You can read more here if you’re interested.

You can only use this system for a maximum of about ten seconds before you use up all your phosphocreatine and are unable to resynthesize any more ATP.

When you see someone lift a weight for 1-6 reps, this system where the majority of the energy is coming from.

Anaerobic Glycolysis

Anaerobic glycolysis is slightly different – you get slightly less power than the ATP-PC system, but it lasts longer (up to about roughly 2 minutes). This system uses glucose (carbohydrates that you’ve eaten) in order to fuel contraction, in a fairly complicated reaction that I won’t go into here. Ok Good.

But How Does That Apply?

After that lengthy explanation, to cause a high amount of metabolic stress in a muscle, you need to exhaust your anaerobic system (anaerobic glycolysis and ATP-PC). This is done optimally with high rep sets that take longer than ten seconds – this exhausts your ATP-PC system and begins ramping up anaerobic glycolysis.

This is where you feel a burn in the muscle and often end up with the “pump”. The extra blood-flow is a side-effect of this system working to generate ATP.

But hang on Tim.

You said at the start that you don’t need a pump to build muscle. And you don’t, which I will explain right after we talk about muscle damage. Which is coming right up.

Muscle Damage

This is the shortest and sweetest of the three. To get muscle damage, all you need to do is apply a force which stresses the muscle, which is pretty much gym training in a nutshell. This is really side effect of the other two factors – mechanical tension and metabolic stress cause muscle damage.

It has been shown that the eccentric (muscles lengthening under tension) portion of lifting weights is what causes the most muscle damage. Think when you lower a bicep curl slowly.

Also unfamiliar movements – you’ll notice when you try a new bench press or squat variation you tend to be sore – tend to cause a lot of muscle damage and soreness. The soreness is known as DOMS (delayed onset muscle soreness), and is closely correlated to muscle damage. You remember that feeling after your first chest day ever? Yeah, that’s DOMS.

Practically, all you need to know is that when you cause muscle damage, the muscle undergoes elevated protein synthesis, and grows back bigger and stronger than it was previously, in order to be better equipped to handle the stimulus again.

The more you do this – the more you grow.

Ok Great, But What About The Pump?

Ok, you’re thoroughly equipped now to look at hypertrophy from a scientific standpoint. If you want to delve into further, very scientific and complicated detail – check out this literature review. But now we can talk about why training with this high rep, pump based workout style doesn’t necessarily build muscle any faster than lower rep training.


Let’s look at those three factors of hypertrophy again.

Muscle damage is roughly the same with both styles (low/high rep training). With lower reps and heavier weights, the eccentrics (which are primarily responsible for muscle damage) are more stressful on the muscle. With higher rep training, the eccentrics are less stressful, but there are more of them. This roughly equals out.

Moving on, mechanical tension and metabolic stress actually completely cancel each other out!

Think about it, if you use a heavier weight, that places your muscle under more tension than a lighter weight. However metabolic stress (which causes a pump) is minimal here, because reps are lower. However, if you use a lighter weight there is less mechanical tension, but much more metabolic stress! Anaerobic glycolysis has to work a lot harder due to the longer set duration and higher reps.

In this way rep range actually becomes irrelevant (within reason), because mechanical tension and metabolic stress will always act in opposite of one another. You can build just as much muscle with low rep training as high rep training – as long as you’re conscious of something called training volume. Again, we’ll talk about that in a bit.

So What Do You Need To Do To Build Muscle?

I hope you’re not hopelessly confused as there was a fair amount of science going on there.

This is part where I’ll give you the practical takeaways, so really, you don’t actually have to understand too much of the above. Just understand this:

To increase your muscle size – you can increase any of those three factors we talked about before:

• Mechanical tension
• Metabolic stress
• Muscle damage

I would recommend you only increase one at a time. If you try increase all of them at once that would be very hard to handle. Who are you, Mark Wahlberg?

Side note: This is related to periodization – a topic far too big to cover here. I cover it in full detail in this article.

Increasing Mechanical Tension

This is where it becomes fairly simple – to increase mechanical tension, all you need to do is become stronger. Heavier weights = more tension = more hypertrophy. Alternatively, you could slow down your lifting tempo, as slower reps will increase your time under tension. I look at both methods here.

Becoming Stronger

Becoming stronger is quite simple – use a lower rep range (4-6), rest more (2-5 minutes), focus on the compound movements (bench, squat, deadlift, row, strict press, pull-up), and try to incrementally put the weight up every week (by 2.5-5lb). You can see some example splits here.


On slowing your tempo for more mechanical tension – always lift as fast as you can through the concentric (muscles shortening under tension – i.e. the press of a bench press), as this will give you more strength gains. One study showed lifters doubled their bench press gains when pressing as explosively as possible, when compared to a controlled concentric tempo (read more here) The take-home – always perform the concentric explosively and control the eccentric for more time under tension.

If you’re going to slow down your reps – slow the eccentric only. A progressive plan could be increasing all your reps’ eccentric portion by 1 second per week. Stay within reason though – eccentrics over 3-5 seconds will drain your energy for the concentric phase of the lift.

Getting stronger is the best method for more mechanical tension.

Increasing Metabolic Stress

To increase metabolic stress, you require longer working sets which are more taxing on your anaerobic glycolysis system. All you need to do is increase your reps per set. What I would recommend is to have a rep bracket (i.e. 6-10 or 8-16 reps – it doesn’t have to be one those two though, pick your own if you want), which you increase by 1-3 reps per week. Once you reach the end of that bracket, increase the weight and go back to the start of the bracket.

For example, say you bench press twice per week, 8 reps of 185lb. That’s great for your first week, but the week after you go for 10 reps at 185lb. If you miss reps (say you can only get 9), that’s fine, do what you can and try for 10 next week.

The longer you’ve been lifting the harder this will be, so make your rep increase goal sensible. A good guideline is:

• <1 years lifting – 3+ reps per week
• 1-3 years lifting – 2 reps per week
• >3 years lifting – 1 rep per week

Bear in mind everyone is different and works well for one may work not at all for another. Change your goal appropriately and pick a rep range where you feel you progress the best. Some people just respond better to lower rep ranges while some respond better to higher reps.

Experiment. Measure your arm and chest girths and try a low rep block. Try it again with a high rep block. Try and do the majority of your training where you respond the best – do mix things up though!

Increasing Muscle Damage

This is an approach I would not recommend to perform 100% of the time, as muscle damage and DOMS is not fun and can limit future training. Not to mention it’s damn taxing on your nervous system!

The way I would treat it is as a training tool that you can use sparingly, but with off-cycles to allow yourself to recover. As muscle damage is mainly caused by eccentrics and unfamiliar movements, add more of these into your programme gradually.

Run a six week block where you add in one negative set (a set where a training partner lifts the weight up for you, then you lower is slowly over a count of 4-8 seconds) for your biceps and triceps per week, at the end of your workout.

By the end of the block you’ll have accumulated six extra eccentric sets per muscle group, causing much more muscle damage in your arms and spurring more hypertrophy. This can be a great intensity technique to mix up the stimulus on your muscles and spur growth.

Summing Up

Overall, what increasing any one of those three factors will do for you is increase something called training volume. Training volume is specific to individual muscle groups. It is simply the amount of sets you perform on that muscle group, multiplied by the amount of reps per set, multiplied by the amount of weight you used.

Volume = Sets x Reps x Weight Used

For example if you benched 200lb for 10 reps for 3 sets, that is 200 x 10 x 3 = 6000lb of volume on your chest.

Note: This assumes a constant lifting tempo – a longer tempo will mean more time under tension and more growth even though volume is technically the same.

If you increase any one of the above factors of hypertrophy (mechanical tension, metabolic stress, or muscle damage) – you are increasing your training volume. Go back through the article (if you want, I know it’s been a big read), and see exactly how increasing one of these factors will increase your training volume.

The over-arching statement is – to get big, to grow that precious muscle into a physique you can be proud of – you NEED to increase your training volume over time. Science supports it, I’ve explained it, so go get it!

I hope you enjoyed the article. If you’re interested in hearing more of what I’ve got to say, head over to www.razorstrength.com and check out some more of my other articles.

Everything I write (and record – I have a YouTube channel) is all about getting as jacked as you possibly can naturally, coming from a former skinny guy’s perspective.

I’ll see you guys there!


Tim Ross Razor Strength


Campos, G. E., Luecke, T. J., Wendeln, H. K., Toma, K., Hagerman, F. C., Murray, T. F., Ragg, K. E., Ratamess, N. A., Kraemer, W. J., & Staron, R. S. (2002). Muscular adaptations in response to three different resistance-training regimens: specificity of repetition maximum training zones. European Journal of Applied Physiology 88(1-2), 50-60. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/12436270

Folland, J., Irish, C., Roberts, J., Tarr, J., Jones, D., & Williams, A. (2002). Fatigue is not a necessary stimulus for strength gains during resistance training. British Journal of Sports Medicine, 36(5), 370-374. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1724546/

Mitchell, C. J., Churchward-Venne, T. A., West, D. W. D., Burd, N. A., Breen, L., Baker, S. K., & Phillips, S. M. (2012). Resistance exercise load does not determine training-mediated hypertrophic gains in young men. Journal of Applied Physiology 113(1), 71-77. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3404827/

Schoenfeld, B. J. (2010). The mechanisms of muscle hypertrophy and their application to resistance training. Journal of Strength and Conditioning Research, 24(10), 2857-2872. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/20847704

Schoenfeld, B. J., Ratamess, N. A., Peterson, M. D., Contreras, B., Sonmez, G. T., & Alvar, B. A. (2014). Effects of different volume-equated resistance training loading strategies on muscular adaptations in well-trained men. Journal of Strength and Conditioning Research 28(10), 2909-2918. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/24714538

Van Roie, E., Delecluse, C,, Coudyzer, W,, Boonen, S., & Bautmans, I. (2013). Strength training at high versus low external resistance in older adults: effects on muscle volume, muscle strength, and force-velocity characteristics. Experimental Gerontology 48(11), 1351-1361. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/23999311