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The Oxidative System and Strength Training

Performance Training

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Cardio will destroy your strength gains

We’ve all heard some variation on the above comment, highlighting how the progression seen from resistance and/or anaerobic (without Oxygen) training will be diminished with even the smallest amount of “Cardio”.

Trainers and coaches, new to the industry or otherwise, still widely recite the negative aspects of Cardio on any potential strength gains.

To approach this issue, firstly let’s begin by defining what we mean when we speak of Cardio in this sense.

We’ll keep it simple to start, Cardio is the obviously abbreviated term we use for Cardiovascular exercise. Break it down further and we’re talking about the Cardiovascular System specifically, the heart, blood and vessels as well as it’s supporting structures for function.

The purpose of the Cardiovascular System is the circulation of blood, and transportation of nutrients, to and from cells in the body. We’re talking about a closed system that constantly replenishes us with what we need to stay alive.

In combination with our Lymphatic System, the Cardiovascular System joins to create our basic Circulatory System.

With this definition in mind, we can make the assumption that anything that involves raising of heart rate and increasing circulation is therefore Cardiovascular training, in some respects this isn’t wrong…

Yet what do we actually mean when we use the label Cardio?

When we think of this type of training, many of us are quick to visualise slow, long distance activities that involve the use of monotonous machines that quickly leave us bored at the prospect.

Is this type of activity directed specifically in our goals towards our Cardiovascular System, for the improvement of transportation and circulation as defined, or are we actually talking about something different?

For this we need to take a look back at our basic Energy Systems and see what’s going on here.

In general, we seem to hold these widely assumed characteristics of what we term Cardio, low intensity, long duration. When we review our Energy Systems, under this definition therefore, we are entering the world of the Oxidative System.

As a quick recap from a previous introduction to Energy Systems, the manner in which we can transform energy within the body for use within exercise and activity, can be described at its very simplest of terms, as either requiring Oxygen (aerobic) or not requiring Oxygen (anaerobic) for metabolism.

Resistance Training for Strength/Power purposes, is widely considered to be an anaerobic activity due to the volume/intensity/duration at which weight is lifted requiring the use of mainly anaerobic energy sources, as we will expand upon in the paragraphs to follow.

Cardio however, by our own definition, requires near complete use of aerobic energy production due to its long duration/low intensity characteristics. We could therefore consider it the opposite end of on a spectrum.

When we consider these polar ends, it becomes quite clear as to why statements such as those with which we began, still exist. Utilising two ends of the spectrum simultaneously doesn’t seem to make a lot of sense.

Moving past the pedantics of defining terminology, this Insight is designed to outline that not only should Cardio, or as we’ll term from now on Oxidative Training, form part of your weekly sessions for the obvious cardiovascular benefits, but it may be one of the defining characteristics of how to get fundamentally stronger

  • It’s at this point that we must introduce a small caveat. If you are a highly competitive athlete that competes within single-effort, purely anaerobic activity, 100m Sprinter, Powerlifter, Olympic Lifting for example, you’re an exception to this training methodology due to the uniqueness of the performance environment with a single-effort requirement. This will form part of a subsequent Insight as to why at a later date, TBC…

If you’re a  regular gym-goer or weekend-warrior, team (Football, Rugby, Netball…) or individual-sport athlete (Badminton, Squash, Tennis…), requiring repeated bouts of activity  (i.e. perform, recover, go again) at any level, meet your new best friend, the Phosphagen-Oxidative System.

An understanding of this system is vital in ensuring that your training is goal-specific with the intention of developing transfer into the types of activities you take part in.

If you haven’t already, please take a few minutes to read through our training Insight into Energy Systems and Energy Substrates, both will provide some clarity for our expansion on the topic here.

As a brief overview;

We have four substrates for use in energy production:

  • Creatine Phosphate
  • Carbohydrates
  • Fats
  • Proteins

It’s from the breakdown and free-energy transfer of these molecules, that we can replenish the currency of our body, ATPAdenosine Triphosphate.

For this breakdown and resynthesis to occur, we have three major systems at play;

1) Phosphagen System (also called the ATP-PCr System)

  • Breaking down of ATP to ADP (Adenosine Diphosphate) and subsequent resynthesis using the enzymes ATPase and chemical compound Creatine Phosphate

2) Glycolytic System

  • Breaking down of Glycogen into Glucose (Glycolysis) for resynthesis of ATP via metabolism of Carbohydrates

3) Oxidative System

  • Breakdown of Glucose for use within subsystems for ATP replenishment, achieved via metabolism of Carbohydrates, Protein or Fats (Intensity vs Duration dependent)

Each of these systems have their natural benefit towards the type of activity we’re performing at any given time, both in execution and recovery. Yet as our introduction stated, for the purpose of this Insight, our focus will be on the two key players for our target audience, the Phosphagen and Oxidation System.

In intense workouts, many of us will have pushed ourselves to the point of feeling that hot, acidic burn within our muscles.

In line with this, we’re all fairly familiar with the cause, and term we apply, to this feeling… the dreaded build up of Lactic Acid…

However, we’d like to very quickly dispel this myth from the outset.

Lactic Acid has never, and will never be formed in the body. It simply doesn’t exist. There exists a fundamental misunderstanding regarding what’s happening in the body when we experience this sensation.

What is produced however is Lactate, a chemical outcome from the conversion of Pyruvate, an end-product of Glycolysis, into a usable form to enable resynthesis of ATP in subsequent reactions. It’s a component of metabolism, not the result, and its presence has little to do with the sensation attribute to the fictitious Lactic Acid…

Why does this matter?

Because it brings us neatly onto what’s actually important in the body and what really causes us to feel this way during high-intensity exercise with limited recovery.


Yes, Hydrogen, the single most abundant chemical on our planet. It quite literally gives life.

Why is Hydrogen present in the body during exercise?

When we consider the key benefits of generating ATP, we have the obvious advantage of providing energy for use within activity. We can move, exercise, metabolise, generally stay alive. All a result of this energy transfer caused by the breakdown and resynthesis of ATP.

What we often fail to consider in out thought process, is the secondary purpose of our function, bi-product threat management.

Hydrogen is a natural bi-product of the Hydrolysis (breaking down) of ATP. As the name suggests, Hydrolysis requires the presence of water for the reaction to occur.

If we take a look back at our basic breakdown of ATP, we’ll see it’s presence.

ATP + H2O  (Water) + ATPase = ADP + P + Energy + Hydrogen + Heat

In this metabolism, we use Hydrolysis in conjunction with ATPase, the enzyme that catalyses the breakdown of ATP, in breaking off a molecule of phosphate and generating our transfer of free energy.

However we’re left with a number of bi-products on the right of our equation as a result…

  1. ADP
  2. 1 Phosphate molecule
  3. Heat 
  4. 1 Hydrogen molecule

With ADP and 1 Phosphate molecule, we have the building blocks of ATP resythesis, no problem here.

However, as humans we have two big threats to our systems from this necessity for ATP breakdown/production for survival.

  1. The amount of heat we generate
  2. The level of Hydrogen within the body

Get too hot, and the system breaks down for obvious reasons through loss of allostasis. However, we have obvious mechanisms in the body to naturally prevent this, sweating would be a perfect example of this.

Yet dealing with Hydrogen is another matter entirely. The presence of Hydrogen is what alters blood pH towards acidic levels. Its unmodulated build up is what results in those memorable occruances with the so called Lactic Acid we all assume has occurred in our bodies.

Yet the design of each of our energy systems is to allow for replenishing of ATP supplies and the manageable Hydrolysis of ATP and its bi-products in response to exercise duration and intensity.

When we consider this management of threat to these bi-products in each of the Energy Systems, we begin to understand the role that each may have in managing the system balance.

ATP-PCr/Phosphagen System:

ADP + Creatine Phosphate = ATP + Creatine

This is a fairly simple one-step process of rephosphorylation to begin. Simple input, simple output.

Yet this system has no mechanism within to deal with the bi-products of both Hydrogen and heat that where created on breakdown of ATP to ADP, as shown in our Hydrolysis equation.

ATP + H2O  (Water) + ATPase = ADP + P + Energy + Hydrogen + Heat

We therefore see rapid onset and intensity or ATP breakdown for energy transfer, but with minimal sustainability of the system to provide the ATP needed.

Our Glycolytic System however, increases in complexity, seeing a small reduction in intensity but a greater capacity for duration compared to the Phosphagen System.

In the process of generating the 4 ATP molecules we produce from running the Glycolytic system, we lose 2 ATP molecules in the process. This occurs over a process of 10 enzymatic steps as illustrated below.

However, as part of the process, unlike our previous system, one of our enzymatic reactions (Step 6) takes two molecules of Hydrogen out of the equation. It therefore contains an inbuilt mechanism within the process that removes the build up of Hydrogen that occurs during Hydrolysis of ATP.

This however, is both a strength and a weakness of the system. Indeed, it can remove 2 molecules of Hydrogen, but what happens when our breakdown of ATP and Hydrogen production outweighs the capacity of Glycolysis to remove the bi-product?

Welcome back that hot, acidic, burning sensation we have from intense, moderate duration exercise. Not lactic acid, but Hydrogen accumulation…

Nothing compares to the capacity of the Oxidative System to manage not only ATP rephosphorylation, but management of Hydrogen and heat. In it exists multiple methods of which to replenish ATP and reduce the threat of hydrogen in the body.

Of these methods; the Krebs Cycle, Electron Transport Chain (ELC) and Beta Oxidation, it’s the capacity to shuttle the chemical Nicotinamide Adenine Dinucleotide (NAD), in combination with Hydrogen, from the Krebs Cycle to the ELC and back again, that provides this unique system capacity.

Through training, we can develop an unbelievable efficiency in this transportation system. Delivering NADH (NAD + Hydrogen) as a product of the Krebs Cycle, into the ELC for the generation of 28 ATP molecules, benefitting from the added bonus of the removal of the carrier Hydrogen molecule each time, returning back to the Krebs Cycle in its original form, NAD, for a few more rounds of transportation.

High-yield ATP production, Hydrogen removal and heat management, this has everything we look for in a effective, efficient, Energy System. Hence, why it can literally keeps us going for hours on end.

So after all this background Science, how does this apply to the use of Oxidative Training (Cardio) for improvements in Resistance Strength and Power Training?

Let’s add the pieces together of what we know so far…

  • Strength/Power Training is predominately Anaerobic Energy System usage (explosive, high intensity, short duration)
  • These Anaerobic Energy Systems cannot resynthesize ATP quickly enough for prolonged activity
  • They also contain limited capacity for the removal of bi-products such as Hydrogen
  • Build up of Hydrogen is limiting factor in recovery and performance

If we don’t have a robust Oxidative System that allows the effective resynthesis of ATP and remove Hydrogen during recovery, training begins to become Glycolytic.

Though energy production may be fractionally higher for ATP (2 molecules produced) during Glycolysis, we still don’t have an effective means of removing Hydrogen on a large scale (2 H+ molecules removed for 2 ATP produced) and thus performance will diminish.

At this late juncture, a practical example to illustrate may be useful…

Client A and Client B are both performing a high-intensity activity for a set duration with a standardised recovery period. Lets say a weighted Prowler Push (10secs duration) followed by 60secs of recovery for 10 rounds.

Client A has a questionable Oxidative System, pushing the Prowler a few times sees a diminishing return on intensity. Each time they end an anaerobic burst of activity, they lack the capacity to fall back on a developed Aerobic system on completion to maximise recovery. Their session is becoming more and more Glycolytic with every repetition. It starts to burn, performance drops dramatically.

Client B has a robust Oxidative System. They push the Prowler with high intensity for the duration, maximising the capacity of their Phosphagen System, and immediately begins to recover, all the while relying on the Oxidative System to replenish ATP in vast quantities and remove any harmful bi-products. Their recovery time ends and they go again… and again… and again.

As Client A is falling deeper and deeper into a acidic bath of muscle burn, Client B performs high-intensity rep after high-intensity rep.

It’s the same workout for both, yet we see vastly differing responses… Why?

The Oxidative System powers the capacity for Client A to recover from anaerobic activity optimally.

We’ve witnessed this time and time again in sessions. Set One we hit target weight/volume, Set Two, we struggle hitting the number of reps assigned, Set Three we miss it drastically, we increase the rest time (increasing oxidative recovery…!!!) and still fail on Set Four and Five.

We don’t recover quick enough to perform repeated bouts of exercise at high intensity.

Sure, more direct strength work may develop a greater overall output, as well as an increased tolerance towards this type of activity, but the key lies in the basics of Physiology.

There is inherent value across the entire spectrum for developing a robust Oxidative System.

So how do we apply this into our training?

Firstly, we take a look back into the requirements for development of our Energy Systems and look at this from two aspects;

  1. Exercise Recovery
  2. System Development
In terms of the development of our Anaerobic qualities (Strength/Power), Oxidative Recovery is a crucial part.

This is not to say we turn all repeat-bout individuals into aerobic monsters a la Marathon Runners (a conversation for another Insight entirely). But if we stress our Phosphagen System with short, highly intense bursts of activity, we need to maximise Oxidative Recovery to ensure we can go again at the same intensity in the shortest possible recovery period using the most efficient means possible.

Understanding work-to-rest ratio, or better yet, individualised Heart Rate Zones, is a fundamental component of personalising a workout to the individual at hand and maximising Energy System usage.

As a general guideline, Creatine Phosphate resynthesis (a requirement in ATP replenishment in the Phosphagen System) takes approximately 8 minutes. If you want maximal power output, be prepared to wait for that full recovery until the system allows.

Complete resynthesis of ATP, occurring primarily through Oxidative means, takes between 3-5mins. If you’re strength training in the lower rep range (3-5 reps or 3-10sec in duration) and this is your assigned recovery, you’ve got a decent shot at hitting your maximal numbers, any less and expect under-recovery to be a limiting factor.

Working above this rep range or duration and things will start to get Glycolytic. The key here is developing a buffer to Hydrogen build up without it becoming a repeat performance inhibitor, whilst improving Oxidative capacity to further aid in recovery.

Remember, the quickest way to replenish these systems is through our Oxidative methods, high ATP yield and effective Hydrogen removal.

But why stop there?

As previously stated, this DOES NOT require hours upon hours of tedious, long distance activity.

The longer the duration extends, the increased likelihood of Protein being utilised as an energy substrate within the Oxidative System due to alternate source depletion.

Adding in a simple 20-60mins of steady-state continuous activity on recovery/low intensity days, holding Heart Rate between 120-150bpm – 1/2 per week, is an incredibly beneficial method of creating that Cardiac Output development, as well as aiding in the recovery process through the use of Oxidative System capacities for regeneration.

For a more intensive targeted workout that develops the capacity to buffer against Hydrogen production, 10-20mins at +/- 5bpm Anaerobic Threshold (85-90% HR Max) with 1-3 repeats, will extend your ability to maintain high-intensity exercise before the Glycolytic System takes over the system entirely.

Here lies the power of our Phosphagen-Oxidative System. If you take part in any form of activity that requires you to perform repeated bouts of activity, the basic sciences are strongly in favour of combining the benefits of the Phosphagen System with the Oxidative System.

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