Blog
03
02
2019

The Pump – What is it and what is it good for?

The pump… Akin to sex if you ask Arnold and for most lifters the determinant of a great workout and justification for a selfie.

But what is the pump?

Does it lead to muscle growth?

Is the pump a useful measurement in hypertrophy training?

What is the Pump

The pump is the feeling within a muscle after a hard and fatiguing set, typically achieved with moderate-higher rep training where the muscle become enlarged and ‘swollen’. It feels as though the muscle is burning, the skin as though it is about to split, which can be extremely uncomfortable in the periods immediately following the completion of a set. In many cases a good pump can also create the optical illusion that an individual is larger than they actually are.

A bitter sweet experience…

What causes the pump

When we lift weights, there are a number of neuromuscular processes that occur that lead to the sensation of the pump.

The external resistance aka tension placed on the body results in the nervous system (the software) recruiting the motor units within an individual muscle fiber (hardware). These fibres are recruited from smallest to largest (the size principle) depending on the magnitude/duration of tension and peripheral fatigue experienced leading to increased force production at slower velocities (force-velocity relationship). The fibers lengthen and shorten via the actin and myosin cross bridging cycle moving the bones and voila a rep is performed and gravity defied.

This is a very basic bitch overview of the process of muscle contraction, but serves as the foundation of understanding why and how a pump occurs.

For a more detailed and comprehensive insight into the physiology of muscle and how it grows, check out this article HERE.

I’m sure many of you are aware that as a set is taken closer to failure especially with higher rep training the sensation of the burn.

At a physiological level, the pump is likely due to a combination of two things:

  1. Metabolite build up within the muscle; and
  2. Increased motor unit recruitment and subsequent fatigue of training using light-moderate loads with a close proximity to failure – leading to the sensation of effort.

The pump and metabolic stress are used synonymously by many and a commonly held belief is that the sensation of cell swelling is a useful determinant of not only an effective workout, but muscle growth.

So let’s examine this further…

What is metabolic stress & does it cause muscle growth?

Simply put, metabolic stress is the accumulation of metabolites induced by exercise, such as lactate, inorganic phosphate and hydrogen-ions. This primarily occurs when anaerobic glycolysis is the primary source of energy production for exercise.

It is commonly believed that the accumulation of metabolites that occurs during resistance training elicits a “metabolic stress” to the muscle fiber, and triggers a host of anabolic singling pathways, in a similar way to mechanical tension.

The theoretical model of how metabolic stress induces hypertrophic adaptations includes five key elements:

(1) Motor unit recruitment,
(2) Systemic hormone release,
(3) Muscle cytokine (myokine) release,
(4) Reactive oxygen species release, and
(5) Muscle cell swelling.

All of the above are thought to contribute to growth, but if you read this article HERE you will see why perhaps metabolic stress may only be correlated with muscle growth and NOT causative of growth.

Cliffs: The peripheral fatigue associated with hard training contributes to muscle growth by increasing motor unit recruitment and decreasing muscle fiber shortening velocity during strength training. These changes increase the mechanical tension experienced by the muscle fibers controlled by HTMU’s. So, as it stands, mechanical tension (the actual magnitude/duration of loading) is what appears to be causing the necessary changes in physiology that lead to hypertrophy, not necessarily the metabolite build up associated with the pump.

As a result, many have now assumed the position that the pump/burn is irrelevant for muscle growth.

However, I’m not so quick to dismiss the pump or metabolic stress as metrics in training for hypertrophy.

If you’re getting a muscle pumped, it’s likely that tension is being placed on the muscle and it may be indirectly predictive of growth, given that muscle groups that are most easily ‘pumped’ seem to grow the most.

Furthermore, in many cases when a pump is achieved, so too is fatigue. Both of which are very necessary when the goal is to get yolked.

I mean, there aren’t many folk who can get a wicked pump brushing their teeth. And brushing your teeth hardly exposes the muscle tissue to any significant magnitude of tension or fatigue, right?

Furthermore, whilst the pump/metabolic stress may not cause growth, in my experience they are useful metrics in training for a number of other reasons.

A case for monitoring metabolic stress aka the pump

1. Lift Execution

The pump has a great deal of utility in assessing the execution of a lift and how effectively the stress/tension was distributed to the target muscle (especially in isolation exercises). Getting a good pump during a set for a particular body part is a great indication that the muscle is being recruited.

If you’re getting wicked pumps in the right muscle(s), chances are you nailed your technique during a set and have exposed the muscle(s) to the tension necessary to cause growth.

If you lift with a poor range of motion, use excessive momentum to assist in completing reps or have poor form, then chances are the tension isn’t going to the muscle – theres a lot of leakage.

2. Focus of Attention

The pump can also be a great measure for focus of attention during a set/workout. During isolation exercises, an internal focus of attention (such as squeezing the muscle) has been found to increase muscle activation. If you are getting crazy pumps and metabolite build up (especially during isolation exercises), then chances are your attention is focused in the right area for single joint exercises.

If you’re getting distracted in a session, taking too long between sets, losing focus mid set or not mentally switched on, the pump can be diminished.

3. Fatigue Management

The pump can also be an assessment of residual fatigue accumulation. If recovery costs associated with hard and overloading training (central/peripheral fatigue, muscle damage or psychological stress) are chronically high (exceeding your recovery capabilities) then my experience has shown that pumps will generally diminish.

This can be useful in knowing when to reduce volume or deload or vary the stimulus to prevent non-functional overreaching.

4. Dialling in Pre Workout Nutrition

The degree of pump achieved within a set can be a gauge of appropriate pre workout nutrition strategies – aka better pumps are often associated with a well designed pre workout meal.

If I’m not ticking the boxes when it comes to macro/calorie and timing of my pre workout meal, I really struggle to get swole. Conversely, if I really dial in my pre workout nutrition (all else being equal) then the pumps and improvements in my sessions are noticeable. Therefore if your getting average pumps, you pre workout nutrition may be sub-optimal and need addressing, which can improve performance and in turn growth.

5. Glycogen Depletion

The pump can be a proxy for glycogen depletion, which is a function of energy restriction. This is important in the context of fat loss, as it can highlight the effectiveness of the diet itself in creating a calorie deficit. Additionally, in glycogen depleted states (during extended periods of energy restriction), decrements in performance are inevitable. Thus, the pump or lack thereof can help foresee a decrease in strength, which is useful for a number of reasons such as load/volume selection etc.

If you’re feeling overly flat for long periods of time, then the diet is working (which is great) and your performance will likely take a hit (not so great) and you will often need an adjustment in your program.

In closing…

Whilst the pump may not be a causative factor of muscle growth, it does indicate the presence of fatigue and can be a proxy for the effectiveness of your training and dietary strategies. Therefore, whilst it may not be a wise idea to continually chase pumps in training if your goal is to look like Arnie, keeping close tabs on your ability to feel the sensation of being ‘swole’ may be useful for other reasons.


author: Jacob Schepis

Jacob Schepis is the director of JPS Health & Fitness and one of Melbourne's best personal trainers. As Head nutrition consultant and Strength and Conditioning coach at JPS Health & Fitness, Jacob has transformed hundreds of physiques with his no nonsense, evidence based approach to training and nutrition!