Muscle pump

Geschatte leestijd: 13 minuten

“The pump”, or “muscle pump” is the well-known muscle-enhancing effect of muscles engorging with blood during a workout. Is this effect merely temporary, or does it also contribute to muscle growth in the long term?

The Muscle Pump

What exactly is this “pump” that bodybuilders always rave about? In “Pumping Iron”, Arnold Schwarzenegger tells us he’s coming day and night. Not because he had so many groupies following him, nor because I’m talking about the X-rated version called “Pumping Irene”.

He says this because, according to him, the feeling of “the pump” is comparable to an orgasm. Although he later stated that it was somewhat exaggerated for the documentary, “the pump” is what millions of gym members aim for daily in the gym.

But what exactly is this “pump”, or “muscle pump”? Merely a temporary effect of increased blood flow to the muscle? A temporary and motivating glimpse into the future when you look in the mirror after training and think: “Damn, I look good. This is going well!”. Or rather a misleading and demotivating factor when you look in the mirror the next morning and see none of that effect?

The “pump” is all this and more. In this article, I will delve into what exactly causes “the pump” and what its effects are in the long term.

Also read the article: the workings of muscles

What Causes the Muscle Pump?

The pump has to do with differences in fluid balance both inside and outside cells, caused by a specific type of training [1,2]. When muscle fibers are tightly contracted, there is compression of the veins that carry blood away. However, the arteries that bring blood in remain open. Think of it as a balloon with a hose supplying water and another hose on the other end carrying the same amount away. If you squeeze the outgoing hose while the incoming hose remains open, the amount of water in the balloon will increase, and it will swell.

However, it’s not that simple. The blood brought to the muscle cell via the artery eventually arrives through smaller capillaries. Due to the pressure in the muscle cell, plasma leaks through small openings in the capillaries to the outside where it lands in the spaces between the cells (interstitium). This, in turn, causes so much fluid in these spaces that a part is pumped back into the already filled muscle cells. The muscle cell is thus filled with an excessive amount of blood (reactive hyperemia) [3].

This enhanced reperfusion results in a phenomenon commonly referred to by sports scientists as “cellular swelling” and by bodybuilders as “the pump,” whereby muscles become engorged with blood.

B.J. Schoenfeld,  Auckland University of Technology

Different Factors for Muscle Growth

I’ve taught myself to only look in the mirror in the morning, right after getting up. Then I see myself as I really look. Most want to look right after training when the muscles are pumped and they look much more impressive than usual. What works better for your motivation is personal. Especially when you start training, the pump can be incredibly motivating. It’s like you see immediate results from your training which is very encouraging to go train again the next day, especially when the effect is gone the next morning. The pitfall for beginners, however, is that they train the same muscle group(s) again the next day to see that pump again (usually chest and biceps). This, of course, is at the expense of the recovery from the previous day and thereby at the expense of real growth.

However, the question is whether the muscle pump itself was really just a temporary effect while the real results will be smaller and delayed. Research from recent years suggests that the pump itself also contributes to (real) muscle growth over time.

When we talk about muscle growth, we’re talking about hypertrophy, which is the result of the balance between new proteins that are produced in the muscles from amino acids on the one hand and existing proteins in the muscle that are broken down into loose amino acids. In short, the balance between protein synthesis and protein breakdown [1,6]. This balance is influenced by various factors such as mechanical stress and muscle damage [3].

Many studies have shown that mechanical stress is the main player in hypertrophy [7-11]. Simply training with heavy weights, therefore, that form as much stress as possible on the muscles. The studies that demonstrate its importance did so by working in situations where the influence of important muscle-building hormones was neutralized and muscle growth was still shown. If this was the end of the story, then you might wonder why you shouldn’t just do 1 or a few repetitions with as heavy a weight as possible, as powerlifters and strongmen are accustomed to.

In an earlier article, I already wrote about the discussions between Arnold Schwarzenegger and Mike Mentzer. Mike Mentzer focused mainly on mechanical stress by training as heavily as possible, while Arnold went for more repetitions and thus more muscle pump.

Effect of Muscle Swelling on Muscle Growth

In addition to mechanical stress, muscle swelling also plays an important role in muscle growth [12]. The swelling of the muscle cell is in itself a regulator of certain cell functions [13,14]. For example, muscle swelling stimulates protein synthesis and lowers protein breakdown [15-18]. Especially the fast muscle fibers (a muscle fiber is a cell) are sensitive to changes in fluid balance [4]. This may partly explain why fast muscle fibers are more suited for growth than slow muscle fibers [19-22].

Water Transport Channels: AQP4

These fast muscle fibers contain a high concentration of “water transport channels” called aquaporin-4 (AQP4)[1]. These channels facilitate the transport of plasma to these muscle fibers [4]. The effect of these water transport channels was shown, among other things, in a study where they were deactivated in rats, and a (small degree of) muscle atrophy occurred (muscle breakdown) [24]. However, the rats had to run in a wheel for the study. The rats with deactivated AQP4 ran less far than the rats with active AQP4, so it is unclear whether the decrease in muscle mass was caused by the smaller distance run or by deactivating the AQP4 itself.

Growth as Protection Against Swelling

The exact mechanism is still unknown, but it is suspected that muscle growth caused by muscle swelling is a way to protect the cell from damage. The pressure on the cell walls would be recognized as a danger, causing a signal in the cell that leads to processes that strengthen the cell [3,23]. One of these processes is the production of more protein in the muscles.

Improved Amino Acid Supply Through Hyperhydration

Other researchers point to improved amino acid supply due to the increased moisture content of a pumped muscle. For example, glutamine appears to be supplied better when a cell has more moisture [25].

More Help from Satellite Cells

In an article about the dual action of muscle memory, I explained that muscle growth can also occur because so-called satellite cells in the vicinity of muscle cells can donate their cell nucleus to the muscle cell. With the extra cell nucleus, the cell is able to produce more protein. Research on the workings of creatine (a well-known osmolyte that draws moisture into the muscles) has shown improved recruitment of these (cell nuclei of) satellite cells. A bit like with the rats, however, it is not clear whether this is due to increased hydration due to creatine or due to increased training intensity (and thus higher mechanical stress) due to creatine [26-31].

“Muscle Pump During Training”

Now that you know the theory, I will discuss the practice of the muscle pump below. How do you benefit most from the muscle pump during training? Or rather: How do you cause the greatest muscle pump during training?

Maximum Muscle Pump During Training

For clarity: There are multiple paths to muscle mass. I already briefly mentioned the discussion between Arnold Schwarzenegger and Mike Mentzer about the value of training with a muscle pump. When we see both men on stage, it’s clear that they both use a successful method for muscle growth. Moreover, variation remains important to continue benefiting from a certain type of training. Training for muscle pump is therefore not the only path to muscle mass.

Unfortunately, science cannot tell us much yet about optimal training for muscle pump. There are only a few studies that really looked at the effect of certain types of training on the muscle pump. Based on what we know about the cause of the muscle pump as explained in the previous article, however, we can logically think of many methods.

Muscle Pump Dependent on Energy System

The muscle pump is felt during typical “bodybuilding training” where the number of repetitions of an exercise is about between 8 and 12 with a corresponding weight[3]. In the various articles on this site about energy systems, you can read that with this type of load, aimed at muscle mass, you work partly in the “lactic acid system” and partly in the ATP system.

The body can supply energy to the muscles in different ways depending on the intensity and duration of activity. With this type of load, lactic acid and phosphates are produced, both of which act as so-called osmolytes, substances that attract moisture, causing the muscle to fill up further [1,2].

Maintaining Tension

To achieve a pump, local muscle activation must be high enough to occlude venous output; however, the contractions must be repeated for sufficient repetitions to allow for the pooling of blood.

B.J. Schoenfeld, Auckland University of Technology

It is therefore important that you contract hard enough to close off the veins that carry blood away from the muscles. Otherwise, you might think of doing many light repetitions for a lot of lactic acid. However, firstly, you would then train the wrong muscle fibers, namely the slow ones instead of the fast muscle fibers that are more suited for growth. Moreover, it’s possibly too light to ensure enough contraction to hold back the blood leaving the muscle.

At the same time, enough repetitions must be done to allow enough blood to flow into the muscle. Otherwise, you might consider doing just a small number of repetitions with a heavier weight. The contraction is then strong enough to close off the veins, but due to the small number of repetitions, there is not enough blood to retain and thus cause a muscle pump.

To retain the blood that is pumped into the muscle, the contraction must also be maintained for a long enough duration. This is an important argument for keeping the muscle under tension throughout the entire exercise [3].

Execution of Exercises for Muscle Pump

You can adjust every exercise to keep the muscles under tension for as long as possible [6,7]. For example, I have often written about concentrating on the eccentric phase of an exercise by performing it slowly. If you’re bench pressing, and you let the weight drop quickly, then you’re losing a lot of tension during that eccentric part of the exercise. If you let the weight down slowly, then you retain a larger part of the tension.

For “real” eccentric training, it’s worth noting that this does lead to great mechanical stress on the muscle (see previous article), but not to a great muscle pump. With real eccentric, or “negative” training, you are assisted during the concentric part (because the weight is too heavy for that), where the muscle thus partially relaxes.

In preparation for an interview with (the late) Ed van Amsterdam, I read that he was fond of “one and a half bench presses”. What he did during bench pressing was to follow a full repetition with a half repetition. The half repetition was then the lower part of the range of motion, so the part from where the bar leaves the chest to halfway where you would normally extend your arms. In an interview that never happened due to his passing, I wanted to ask him about the purpose of this.

I assumed that this was because with the half reps the chest muscles are more isolated from the triceps. If you consider that from that point normally the triceps take over a large part of the load and the chest muscles thus work less, such a half repetition is also a better method to optimize the muscle pump in the muscles [3].They get less opportunity to “rest” in the part where the triceps would take over some of the work.

Leave Your Ego in the Locker Room

When you’re getting dressed for training, leave your ego in the locker room. Keeping the muscle under tension throughout the entire exercise means that you will be able to do fewer repetitions or have to work with less weight because it requires much more energy. There’s no rest point in the exercise. If you’re concerned about how much you impress others with the weight you can handle, then you actually welcome that rest point. You’ve seen Ronnie Coleman’s DVDs. So you’re constantly shouting “Lightweight, baby!” where, of course, you want to have the heaviest possible weights in hand to make it clear that the remark is meant to be humorous and not literal.

If you want to pump up your muscles instead of your ego, then don’t swing around with too heavy weights where you do everything to make it as easy as possible for the muscle, but instead make it as difficult as possible by using the correct technique (depending on your goal what “correct” is).

In other words: “Train the muscle, not the movement or your ego”

Dropsets

Think, for example, of dropsets. With dropsets, a set is directly followed by another set with lighter weight. This can be repeated one or several times, for example until you can only do a few repetitions of bicep curls with dumbbells of just 4 kilos. In practice, of course, this is precisely the moment when the prettiest girl in the gym walks by and thinks: “light weight”, but you don’t care since your ego is still in the locker.

Research indeed shows that more lactic acid is produced by going directly to a next set with a lighter weight after a first set. In the 2003 study, a set with 90% 1RM (a weight that is 90% of the weight with which you can do one repetition) was followed by a set with 50% 1RM, 70%1RM, or again 90% 1RM. The dropset thus consisted of only one extra set, while in practice usually several extra sets are done. Continuing with half the weight yielded, despite more lactic acid (and growth hormone) than continuing with 70% or the same weight [4].

Besides the increase in lactic acid, the muscle is also kept under tension longer and thus retains the blood longer.

Two years later, the same Japanese researchers conducted another study that showed that dropsets make muscles grow faster (measured by the size of the cross-section) [5]. However, the comparison with “normal sets” did not ensure that both ultimately came to the same amount of training. Therefore, it is unclear whether the extra growth was due to the method of the dropsets or simply due to the greater training volume.

Type of Exercise

There are too many different exercises and ways to perform them to place an overview here. If you try to feel it out a bit, you can figure out for yourself which exercises keep tension on the muscles the longest.

In general, we see that exercises with cables and machines keep the muscles under tension longer. However, there are many exceptions to this, often depending on the execution of the exercise or the alternative to it. Elastic bands are also very suitable for keeping a muscle under tension during an exercise, although it can be difficult to find the right resistance (they also tend to break quickly in my experience).

For example, with bicep curls with dumbbells, we often see that the upward (concentric) movement is carried too far so that the weight comes to rest on top of the forearm. With cable curls, people tend not to do this as much because you clearly feel that the last bit is pointless. Moreover, the tension stays on the biceps longer until this point is reached.

Tourniquet Training?

So, keeping the muscle under tension is one method to ensure that the veins carrying the blood away are sealed. But what is the effect if you do this directly by, for example, binding your arms or legs with a tourniquet? The answer to that follows in the next (and for now last) article about the muscle pump.

Much Still Unknown

There is still much unknown about the workings of the muscle pump. How long does it last depending on the way the pump was induced? What happens, for example, with the pumped chest muscles if you go directly to training biceps or triceps as most of us do after chest training. Do you then benefit less long from the muscle pump in the chest? Bodybuilders who “pump up” before they have to go on stage often only pump up the smaller muscle groups because they know that blood cannot be present in all muscles at the same time.

Much research will still need to be conducted to truly understand the workings of the muscle pump and to optimally utilize it for muscle growth.

References

1. Schoenfeld, Brad J. MSc, CSCS, CSPS, NSCA-CPT; Contreras, Bret MA. The Muscle Pump: Potential Mechanisms and Applications for Enhancing Hypertrophic Adaptations. Strength & Conditioning Journal: Post Author Corrections: December 23, 2013
2. Sjogaard G. Water and electrolyte fluxes during exercise and their relation to muscle fatigue. Acta Physiol Scand Suppl 556:129–136, 1986
3. Schoenfeld BJ. The mechanisms of muscle hypertrophy and their application to resistance training. J Strength Cond Res 24: 2857–2872, 2010
4. Frigeri A, Nicchia GP, Verbavatz JM, Valenti G, and Svelto M. Expression of aquaporin-4 in fast-twitch fibers of mammalian skeletal muscle. J Clin Invest 102: 695–703, 1998.
5. Sjogaard G, Adams RP, and Saltin B. Water and ion shifts in skeletal muscle of humans with intense dynamic knee extension. Am J Physiol 248: R190–R196, 1985.
6. Tipton KD, Wolfe RR.Exercise, protein metabolism, and muscle growth.Int J Sport Nutr Exerc Metab. 2001 Mar;11(1):109-32.
7. Hornberger TA, Stuppard R, Conley KE, Fedele MJ, Fiorotto ML, Chin ER, and Esser KA. Mechanical stimuli regulate rapamycin-sensitive signalling by a phosphoinositide 3-kinase-, protein kinase B- and growth factor-independent mechanism. Biochem J 380: 795–804,2004.
8. Miyazaki M, McCarthy JJ, Fedele MJ, and Esser KA. Early activation of mTORC1 signalling in response to mechanical overload is independent of phosphoinositide 3-kinase/Akt signalling. J Physiol 589: 1831–1846, 2011.
9. Spangenburg EE, Le Roith D, Ward CW, and Bodine SC. A functional insulin-like growth factor receptor is not necessary for load-induced skeletal muscle hypertrophy. J Physiol 586: 283–291, 2008.
10. Vandenburgh H and Kaufman S. In vitro model for stretch-induced hypertrophy of skeletal muscle. Science 203: 265–268, 1979.
11. Witkowski S, Lovering RM, and Spangenburg EE. High-frequency electrically stimulated skeletal muscle contractions increase p70s6k phosphorylation independent of known IGF-I sensitive signaling pathways. FEBS Lett 584: 2891–2895, 2010.
12. Schoenfeld BJ. Potential mechanisms for a role of metabolic stress in hypertrophic adaptations to resistance training. Sports Med 43: 179–194, 2013.
13. Haussinger D. The role of cellular hydration in the regulation of cell function. Biochem J 313: 697–710, 1996.
14. Haussinger D, Lang F, and Gerok W. Regulation of cell function by the cellular hydration state. Am J Physiol 267: E343–E355, 1994.
15. Grant AC, Gow IF, Zammit VA, and Shennan DB. Regulation of protein synthesis in lactating rat mammary tissue by cell volume. Biochim Biophys Acta 1475: 39–46, 2000.
16. Millar ID, Barber MC, Lomax MA, Travers MT, and Shennan DB. Mammary protein synthesis is acutely regulated by the cellular hydration state. Biochem Biophys Res Commun 230: 351–355, 1997.
17. Stoll BA and Secreto G. Prenatal influences and breast cancer. Lancet 340: 1478, 1992.
18. Lang F, Busch GL, Ritter M, Volkl H, Waldegger S, Gulbins E, and Haussinger D. Functional significance of cell volume regulatory mechanisms.Physiol Rev 78: 247–306, 1998.
19. Aagaard P, Andersen JL, Dyhre-Poulsen P, Leffers AM, Wagner A, Magnusson SP, Halkjaer-Kristensen J, and Simonsen EB. A mechanism for increased contractile strength of human pennate muscle in response to strength training: Changes in muscle architecture. J Physiol 534:613–623, 2001.
20. Adams G and Bamman MM. Characterization and regulation of mechanical loadinginduced compensatory muscle hypertrophy. Compr Physiol 2: 2829–2870, 2012.
21. Kosek DJ, Kim JS, Petrella JK, Cross JM,and Bamman MM. Efficacy of 3 days/wk resistance training on myofiber hypertrophy and myogenic mechanisms in young vs. older adults. J Appl Physiol 101: 531–544,2006
22.  Staron RS, Malicky ES, Leonardi MJ,Falkel JE, Hagerman FC, and Dudley GA. Muscle hypertrophy and fast fiber type conversions in heavy resistance-trained women. Eur J Appl Physiol Occup Physiol 60: 71–79, 1990.
23. Lang F. Mechanisms and significance of cell volume regulation. J Am Coll Nutr 26: 613S–623S, 2007.
24. Basco D, Blaauw B, Pisani F, Sparaneo A, Nicchia GP, Mola MG, Reggiani C, Svelto M, and Frigeri A. AQP4-dependent water transport plays a functional role in exercise-induced skeletal muscle adaptations. PLoS One 8: e58712, 2013.
25. Low SY, Rennie MJ, and Taylor PM.Signaling elements involved in amino acid transport responses to altered muscle cell volume. FASEB J 11: 1111–1117, 1997
26. Dangott B, Schultz E, and Mozdziak PE. Dietary creatine monohydrate supplementation increases satellite cell mitotic activity during compensatory hypertrophy. Int J Sports Med 21: 13–16,2000.
27. Philippou A, Halapas A, Maridaki M, and Koutsilieris M. Type I insulin-like growth factor receptor signaling in skeletal muscle regeneration and hypertrophy. J Musculoskelet Neuronal Interact 7: 208–218, 2007.
28. Zammit PS. All muscle satellite cells are equal, but are some more equal than others? J Cell Sci 121: 2975–2982, 2008.
29. Olsen S, Aagaard P, Kadi F, Tufekovic G, Verney J, Olesen JL, Suetta C, and Kjaer M. Creatine supplementation augments the increase in satellite cell and myonuclei number in human skeletal muscle induced by strength training. J Physiol 573: 525–534, 2006.
30. Vierck JL, Icenoggle DL, Bucci L, and Dodson MV. The effects of ergogenic compounds on myogenic satellite cells. Med Sci Sports Exerc 35: 769–776, 2003.
31. Willoughby DS and Rosene JM. Effects of oral creatine and resistance training on myogenic regulatory factor expression. Med Sci Sports Exerc 35: 923–929, 2003.