A Brand New Day
CC Photo Credit: Thomas Hawk

As far as I know, Energy System Development is a term coined by Mark Verstegen, Founder of EXOS (formally Athlete’s Performance).

Mark’s a smart dude, but also the term obviously describes the intent, much the same way Neuromuscular System Development encapsulates training for the nervous systems and muscular systems.

Most people only know about ‘Aerobics,’ or ‘Aerobic Training,’ or what I often hear people talk about in terms of ‘cardio,‘ and maybe a few refer to as ‘conditioning.’

Aerobic simply means, ‘with oxygen,’ and only compromises one of three energy systems.

Two are actually Anaerobic Pathways — which if you’re wondering, basically means, ‘without oxygen.’

We are capable of producing energy in an oxygen environment and in an environment exclusive of oxygen.

Oxygen is a catalyst for energy production, your aerobic energy system is actually far more efficient at generating energy via the production of adenosine triphosphate (ATP) — the most basic component of energy that your body utilizes — but at the expense of speed and a lower power output.

You can’t sustain a high level of energy output for too long, before the aerobic system must kick in to cope with the energy demands.

The other obvious drawback is that exclusive training of the aerobic system won’t really contribute much in the development of the other two energy systems, while training the other two energy systems leads to dramatic improvement of the aerobic system, as shown most notably in the Tabata Study. Though keep in mind that those involved in that study, still did about seventy minutes of aerobic work per week. Something to think about…

Too much time spent in the mythological ‘fat-burn zone‘ or too much low-level aerobic training is often thought to lead to the degradation of muscle tissue, making your body less metabolically active throughout the day.

However, most of that has to do with shear energy balance, and the fact that people can’t keep their energy balance above maintenance levels. Burning more energy than you take in, without the protein intake and resistance training to support muscle retention, will degrade more muscle tissue, even in the absence of aerobic training.

Thus, spending some time training in that aerobic zone is usually a good idea, all the same. Higher intensity forms of exercise thicken the walls of the heart when done to excess, while aerobic training results in greater elasticity of the heart. That quality appears to be associated with better heart health, even though higher intensity forms of energy system training still yield a lot of the same benefits.

The other important consideration is that aerobic training improves recovery from strenuous exercise and helps you recover better between sets of higher intensity exercise.

Basically everything has it’s pros and cons, you should be aware of that, and then cater your ‘cardio’ to improve what’s important to you.

1. The Quick System

AKA: ATP-CP Phosphagen System (Alactic Anerobic Energy System)

This is your immediate or shortest duration energy system, lasting roughly no longer than 10 seconds.

You’ll find this energy system heavily involved in sports like javalin, shot-putting, American Football, Baseball and short sprints.

It basically uses the ATP stored directly in your muscles, to produce energy quickly.

It’s actually a pretty powerful energy system, but the obvious limitation is endurance. It’s questionable how trainable this system actually is.

A lot of NMSD is actually geared to this system and strength training, particularly explosive strength, with less than 5 reps is often within this system already, but in terms of everyday health and performance an ESD day of training geared to this system most likely has sprint variations of an exercise with longer periods of rest.

For example, a 10 second sprint followed by 60 seconds of rest. Sprint intervals like this are often characterized by quick or short duration work periods, with longer rest periods as high as ten times the duration of the work portion.

Often energy system work in this realm is characterized by 6-20 times the amount of recovery relative to your work period, or enough time to allow a chemical process to restore ATP again within the muscle. Depending how how high the intensity is, or you want it to be.

For example, 40m, 60m, 80m and 100m sprints are mostly geared to this energy system, and are among my favourite protocols for maintaining cardiovascular fitness via this system.

Often I’ll just do a quick sprint, walk back slowly and repeat.

However, sprinting is also technical, so you need to show technical proficiency to work on them, otherwise you’re best off with a bike, rower or something with less of a learning curve.

The nice thing about this type of training, is that you can do significantly less but get great health benefits, while better preserving metabolically active muscle tissue, so they are relatively time efficient. If you discount the fact that you need long rest intervals anyway.

Personally, I’d rather sit around for a few minutes between bouts of intense exercise, than to do mindless steady state work — though I still force myself to do some of that too…

The more work you do in this realm, the more muscle mass is also likely to be preserved (by comparison to the other two), but in my opinion shouldn’t be at the expense of occasionally working on the other two energy systems.

The downside of this type of training is that it’s hard to recover from, so you can’t do it often and it’s questionable how much you can do in conjunction with resistance training (not very much as they are very similar).

Most sprint coaches theorize that this kind of work can only truly be tolerated about twice a week, some might lean to a max of three times a week, but the consensus on this type of training is generally unanimous in the sense that you need more recovery time when utilizing higher intensity training protocols.

About 72 hours or more for high intensity sprint work that is above 90% effort or close to 100%.

Some coaches also question the trainability of this energy system, noting that improvements to the energy system itself seem moot relative to the neuromuscular improvements. I don’t completely agree.

I’d note that big improvements within a 10-12 second interval can be less than tenths of a second. A tenth of a second is the difference between first and third at the most recent Brazil Olympics for the 100 m, or less than the difference between third and sixth for more perspective.

I recommend using it sparingly a few times a year, in low doses (less than 20-30 minutes not including warming up), followed by resistance training (rather than on separate days), with aerobic training done on off days to aid in recovery.

It is however more relevant for athletes in power sports than the average Joe or Jane.

2. The Medium System

AKA: Glycolytic System (Lactic Anaerobic Energy System)

The glycolytic system or your sugar system, still requires energy expenditure in an environment without oxygen like the ATP-CP system, but after about 10-12 seconds the body basically starts utilizing simple carbohydrates or glucose as a fuel source, rather than pure ATP.

Sugar requires some breakdown and chemical changes to occur for this system to be effective and training this system leads to a better utilization of glucose and a greater duration of exercise at a higher intensity.

This system is predominantly used in Power Sports like Soccer, Basketball, Hockey, Rugby, and 200m, 400m, 800m track events.

The downside?

Lactic Acid build-up, which isn’t as bad as most people think, however, it still creates a burning sensation as your body produces the acid  — which is actually a fuel source, basically your body in an anaerobic state produces lactic acid  — and eventually will disallow you from continuing at that intensity.

This is also often referred to as the Lactate Threshold or Anaerobic Threshold (whatever you want to call it), but your body is good at dealing with it for about 90-120 seconds, depending on training, before it has to start utilizing the aerobic energy system and your power output has to drop.

It’s maintaining this intensity past your initial threshold, that makes training this energy system so vital, in so many activities.

The nice thing about this system though, is that with a little bit of rest, you can tax it pretty heavily and train a lot of similar qualities to your aerobic system at the same time — as a side note, these energy systems actually have a bit of a cascade effect in that ATP-CP can contribute to Glycolytic System development, which can lead to Aerobic system development, but the opposite is not true, you can’t train your aerobic system and significantly develop your ATP-CP system really.

Your energy systems work together, not in isolation.

A good example of training protocols that develop this system would be 30 seconds on, 60 seconds off intervals or basically anything where the work is less than about 2 minutes and characterized by at least an equal amount of rest but upwards of three times the amount of rest to work, in terms of a ratio, or even less rest than work, as in the Tabata protocol.

Less rest to work ratios typically mean you can’t hold out as long, which is why the basic Tabata approach is only 4 minutes — though contrary to popular opinion, there was still about 70 minutes of steady state aerobic work in that study, everyone conveniently ignores…

If you want to improve fatigue resistance, you lower the rest interval, if you want to improve the quality of the contribution of the glycolytic system to training, you typically use longer rest intervals, especially as they relate to sports.

45 seconds on, three minutes off, as in most hockey shift scenarios, is still an example of Glycolytic Interval Training.

*Note more rest is needed when training the quick energy system, less for the medium, and even less for the long system.

One of my favourite and according to Dr. Steven Boutcher at the University of South Wales, perhaps the most effective for fat loss (per time spent, and if using a bike for comparison), is an 8 seconds on, 12 seconds off protocol. 

A major advantage to this protocol, is that the rest permits you to keep your output fairly high, though the majority of the work ultimately ends up in the aerobic training realm. Try it for 4-5 minutes.

Interval training in these zones, has been shown to make significant improvements in markers for aerobic and cardiovascular health. However, their positive influence over insulin sensitivity might also be useful for weight loss, improving metabolic rate and muscle mass maintenance.

You can also limit training in this area significantly, perhaps even to only 20-30 minutes or less in a training session, while getting similar results (or better) to the typical long-slow distance aerobic work that many people still do for fat loss and weight loss.

In a pinch it’s a great substitute for longer more boring styles of aerobic training, but again, you might not want to utilize it more than two (maybe three) times a week for optimal use.

Typically you’ll still need about 36+ hours of recovery between bouts for ideal performance. You can’t just use high intensity training protocols all year round either, despite how some people might approach it these days.

Be careful mixing it with resistance training protocols as it’s still relatively high intensity (most moderate set lifting is in the glycolytic zone).

What’s interesting is that a great deal of athletic research indicates that this system can be trained rather sparingly and the benefits last for quite some time. It’s highly trainable.

Meaning the benefits of doing glycolytic training three times a week (I’d skip resistance training this week or use very low volume anyway) for one or two weeks can last 6-12 weeks. Ultimately, you can probably get away with a week of this type of training every 2-3 months, with maybe the odd maintenance session here or there and get a lot of the benefits.

A fun little fact about most interval research is that most of the benefits shown are seen in short windows, and they don’t necessarily continue to advance beyond those windows.

Just because it’s been shown that higher intensity interval training has been shown to be very effective at eliciting metabolic and aerobic improvements, doesn’t mean you should just completely forget about aerobic training.

A lot of people these days hammer the @#%* out of this system in particular, expecting to somehow improve. If that’s you, you might want to consider spending some time on #1 or probably more on #3.

Just saying…

Anaerobic training is stressful on the body and harder to recover from in high quantities. Not to discourage you from using it, but a lot of it usually just ends up being aerobic training anyway.

I recommend a few phases of each type of training each year, with a few sessions here or there, depending on how they are planned to maintain during the rest of the year.

Of course, this all depends on your objectives.

3. The Long System

AKA: Aerobic System

At the end of a high intensity interval training session, your last interval might have as much as 40% contribution of the aerobic system.

In other words, it’s always there, always helping you last longer.

If you have decent aerobic fitness than your resting heart rate will typically be around 60 BPM.

If you’re not there on a regular basis, then you might want to mix more into your routine for general health purposes than the other two for now. I think it’s something worth focusing on maintaining.

This system is predominantly used in endurance sports such as long, typically slow (relative to their power sport counterparts) distance cycling, triathlons, marathons, kayak racing, and swimming.

I get it, it’s boring, I’m not a fan of doing the same thing ad nauseam for long periods of time either.

The main disadvantage being the time requirement (also boredom) but the main advantage being that aerobic training can be done almost daily. It’s much easier to recover from that other forms of energy system training.

It’s definitely associated more so with that, than anything else, but pretty much anything that keeps you at a moderate heart rate (about 130-150 BPM) for 20-30 minutes will have an aerobic training effect. Even brisk walking is of benefit and is worth considering on days you’re not lifting or doing some other form of cardiovascular activity.

Honestly, I don’t recommend average people stretch it out beyond 60 minutes, and I usually keep them in that 20-30 minutes zone because I’d rather more frequency than duration, generally. If you have an endurance sport objective, obviously you’ll have to stretch it out longer than that to 90 minutes.

The aerobic system can handle low-medium intensity activities for about 90 minutes in duration or longer, depending on training.

If you’re ever heard the term ‘bonking’ or are familiar with the practice of ‘carb-loading’ in endurance sports, then you are probably aware of this limit, in that your body can only store so much fuel.

Once you run out of this fuel you can make yourself feel rather sickly. However, aerobic training makes better utilization of fat as a percentage of work, so it’s often effective to combine with resistance training (which preserves/builds muscle mass) for fat loss purposes. That’s why so many bodybuilders use brisk up-hill walking on a treadmill for cutting purposes.

Typically the average human being stores enough fuel for comfortably about 20 miles worth of activity in the aerobic zone, but training can change this, as can genetics.

If your goals are suited to endurance sports, then you will want to do a considerable amount of training this system still.

Aerobic energy system training also what most people seem to think of when they hear the term ‘cardio,‘ but as you can see above, it’s only one of three systems.

It’s more for improving recovery for other things, more than anything else. It stimulates a different part of your autonomic nervous system (parasympathetic) which can lead to improved relaxation and stress relief. Not a bad thing if you’re a high strung work-a-holic these days, whereas the two above might aggravate your stress levels, making things worse rather than better.

Aerobic training is also more associated with cognitive/mood/energy benefits than higher intensity forms of exercise, but there is a lack of research on this for the other two. Most of these benefits appear to need about 20 minutes of aerobic activity strung together though, despite the popularity of short workouts like the seven minute workout (it has benefits, just not necessarily these).

Aerobic activity increases the elasticity of the heart to a much greater extent (higher intensity forms of exercise appear to thicken the heart, though the jury is out as to how detrimental heart wall thickening might be) than high intensity exercise, which may be of significant benefit.

Unlike the Anaerobic pathways, training your aerobic system yields little improvements in speed, power or strength and is associated with degradation of lean tissues.

However, you are mostly in a state of aerobic energy expenditure all day, every day, anyway. So muscle loss probably has more to do with negative energy balance, than aerobic work per-se. Muscle degradation is easily combatted by utilizing some of the other methods above, as well as utilizing resistance training and adequate protein intake.

See: Why Strength Training is Important.

I’ll note that research into this interference effect suggests that non-weight bearing aerobic activities (like biking/swimming) do not have a significant interference effect when kept to less than three times a week for no longer than about 20-30 minutes at a time. Something to consider if you’re attempting to gain muscle via resistance training but want to maintain some different aspects of cardiovascular health along with with.

Walking, is predominantly aerobic, and yields numerous health benefits, not to mention provides many people a much needed break within the day.

I’m not saying Aerobic training is bad or good really. For fat-loss, you can use it more frequently and recover better from it, but it might not have the muscle preserving effects of the other two. Something to consider is that the other two can’t be done as often, nor for as long.

I think a mix is generally best as they have slightly different benefits/downsides.

Going for a walk or light hike between workouts is a great activity for ‘active recovery‘ days and low level blood flow has been shown to reduce muscle soreness from previous workouts.

Even if it’s only a placebo effect, light swimming and cycling (notice non-weight bearing endurance activities…) have also been shown to reduce muscle soreness when done between harder workouts.

Despite popular opinion, there are aerobic methods that don’t include long continuous bouts of exercise. As long as you keep your heart rate in an aerobic zone, sled work can be aerobic, rope work can be aerobic and a variety of interval protocols can be aerobic. Don’t limit yourself to just long slow distance work (that’s how I prevent myself from being bored with it) if it doesn’t appeal to you.

Get a heart rate monitor and keep yourself in that aerobic zone for 20-30 minutes using other methods if you like, or use rate of perceived exertion (5-6 out of 10).

I sometimes like to think of it as breathing through my nose, if you have to breathe through your mouth, there is a good chance it’s become more anaerobic (or is approaching it) so back off, trying to breathe through your nose for the 20-30 minutes can be a reasonable indication that the intensity is low enough to be mostly aerobic.

Either needs to be fairly continuous though, even if you have chosen to use an interval approach.

My recommendation is 20-30 minutes of aerobic training (you could do more if you’re an endurance athlete) with a non-weight bearing modality, on days you don’t lift, or following about 1-6x a week depending on your objectives. Or tack on a little of it after lifting.


It is important to remember that these are more like guidelines, than rules.

We know that all three energy systems work interdependently, so it’s not exactly cut and dry.

For example, working your quick or medium systems, means your aerobic system is in use during the recovery period.

Doing resistance training will provide some benefits to these systems, depending on the type too.

If you want to optimize your training, it’s important to order any energy system work within a training session or workout appropriately, so that the quick energy system is developed first, then the medium system, finishing with the long system.

This is of course assuming that you plan to train 2 or more energy systems within a given session.

Also you are better served utilizing some form or combination of interval training in your weight loss efforts, instead of typical aerobic exercise.

[x_alert heading=”Summary” type=”success”]

  • Train all 3 energy systems on a semi-regular basis.
  • Be mindful of how you integrate these forms of training with resistance training.
  • Place emphasis on the Anaerobic System over the Aerobic System only a few times a year, the rest of the year should probably focus more on the aerobic system (for recovery and heart health), if you lift (and you should). Or at least be mindful of what you can actually recover from.
  • Your Medium Energy System means anything lasting 10-120 seconds, with typically up to 4 times the rest, but more often a 1:2 or 1:3 ratio.
  • Your Long Energy System will last roughly up to 20 miles which is typically where people bonk in Marathons without adequate training, or about 90-120 minutes (depending on your level of training) before your carbohydrate stores are depleted and additional carbohydrates must be consumed.
  • Intervals done in the Long Energy System typically have an inverse work to rest ratio (think walk-run protocol) or even. Often the rest is considerably shorter than the work phase, often 1:1, 2:1, 3:1 or even up to 10:1 or higher.
  • If training more than one system within a given workout, train the systems from quickest to longest.
  • All 3 systems work interdependently, not exclusively, so take most recommendations with a grain of salt.[/x_alert]